LM25119PSQE/NOPB - NATIONAL SEMICONDUCTOR

LO1

LM25119

HO1

CS1

PGND1

UVLO

VIN

VCC1

HB1

SW1

CSG1

RAMP1

FB1

COMP1

VIN

AGND SS1 RT SS2 RES

LO2

HO2

CS2

PGND2

VCC2

HB2

SW2

CSG2

RAMP2

FB2

COMP2

VOUT1 VOUT2

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Design

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.

LM25119

SNVS680I –AUGUST 2010–REVISED APRIL 2018

LM25119 Wide Input Range, Dual Synchronous Buck Controller

1 Features

1• Emulated Peak Current Mode Control

• Wide Operating Range (4.5 V to 42 V)

• Easily Configurable for Dual Outputs or

Interleaved Single Output

• Robust 3.3-A Peak Gate Drive

• Switching Frequency Programmable to 750 kHz

• Optional Diode Emulation Mode

• Programmable Output From 0.8 V

• Precision 1.5% Voltage Reference

• Programmable Current Limit

• Hiccup Mode Overload Protection

• Programmable Soft-Start

• Programmable Line Undervoltage Lockout

• Automatic Switchover to External Bias Supply

• Channel2 Enable Logic Input

• Thermal Shutdown

• Leadless 32-Pin WQFN Package

2 Applications

• Industrial DC-DC Motor Drivers

• Telecom Servers and Routers

3 Description

The LM25119 device is a dual synchronous buck

controller intended for step-down regulator

applications from a high voltage or widely varying

input supply. The control method is based upon

current mode control using an emulated current ramp.

Current mode control provides inherent line

feedforward, cycle-by-cycle current limiting and ease-

of-loop compensation. The use of an emulated

control ramp reduces noise sensitivity of the pulse-

width modulation circuit, allowing reliable control of

very small duty cycles necessary in high input voltage

applications. The switching frequency is

programmable from 50 kHz to 750 kHz. The

LM25119 device drives external high-side and low-

side N-channel MOS power switches with adaptive

dead-time control. A user-selectable diode emulation

mode enables discontinuous mode operation for

improved efficiency at light load conditions. A high

voltage bias regulator with automatic switch-over to

external bias further improves efficiency. Additional

features include thermal shutdown, frequency

synchronization, cycle-by-cycle and hiccup mode

current limit and adjustable line undervoltage lockout.

The device is available in a power enhanced leadless

32-pin WQFN package featuring an exposed die

attach pad to aid thermal dissipation.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)

LM25119 WQFN (32) 5.00 mm × 5.00 mm

(1) For all available packages, see the orderable addendum at

the end of the data sheet.

Typical Application Circuit

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Table of Contents

1 Features.................................................................. 1

2 Applications ........................................................... 1

3 Description............................................................. 1

4 Revision History..................................................... 2

5 Pin Configuration and Functions......................... 3

6 Specifications......................................................... 5

6.1 Absolute Maximum Ratings ...................................... 5

6.2 ESD Ratings.............................................................. 5

6.3 Recommended Operating Conditions....................... 5

6.4 Thermal Information.................................................. 6

6.5 Electrical Characteristics........................................... 6

6.6 Switching Characteristics.......................................... 8

6.7 Typical Characteristics.............................................. 9

7 Detailed Description............................................ 11

7.1 Overview................................................................. 11

7.2 Functional Block Diagram....................................... 12

7.3 Feature Description................................................. 13

7.4 Device Functional Modes........................................ 18

8 Application and Implementation ........................ 19

8.1 Application Information............................................ 19

8.2 Typical Applications ................................................ 20

9 Power Supply Recommendations...................... 35

10 Layout................................................................... 35

10.1 Layout Guidelines ................................................. 35

10.2 Layout Example .................................................... 36

11 Device and Documentation Support................. 37

11.1 Community Resources.......................................... 37

11.2 Trademarks........................................................... 37

11.3 Electrostatic Discharge Caution............................ 37

11.4 Glossary................................................................ 37

12 Mechanical, Packaging, and Orderable

Information........................................................... 37

4 Revision History

NOTE: Page numbers for previous revisions may differ from page numbers in the current version.

Changes from Revision H (May 2016) to Revision I Page

• Moved automotive grade device LM25119Q references to data sheet SLUSD97 ............................................................... 1

• Changed Two-Phase Operation to Two-Phase Interleaved Operation section header....................................................... 19

• Added Interleaved 4-Phase Operation section..................................................................................................................... 20

• Added Two-Phase Design Example..................................................................................................................................... 32

Changes from Revision G (January 2014) to Revision H Page

• Added ESD Ratings table, Feature Description section, Device Functional Modes,Application and Implementation

section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and

Mechanical, Packaging, and Orderable Information section.................................................................................................. 1

Changes from Revision F (February 2013) to Revision G Page

• Changed LLP-32 to WQFN-32............................................................................................................................................. 11

9 10 11 12 1513 14 16

32 31 30 29 2628 27 25

SW1

HO1

HB1

VIN

HO2

UVLO

HB2

SW2

VCC1

LO1

PGND1

CSG1

CS1

RAMP1

SS1

VCCDIS

FB1

COMP1

EN2

AGND

COMP2

RES

FB2

VCC2

LO2

PGND2

CSG2

CS2

RAMP2

SS2

DEMB

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5 Pin Configuration and Functions

RTV Package

32-Pin WQFN

Top View

(1) G = Ground, I = Input, O = Output, P = Power

Pin Functions

PIN TYPE(1) DESCRIPTION

NAME NO.

AGND 12 G Analog ground. Return for the internal 0.8-V voltage reference and analog circuits.

COMP1 10 O Output of the channel1 internal error amplifier. The loop compensation network must be connected

between this pin and the FB1 pin.

COMP2 15 O Output of the channel2 internal error amplifier. The loop compensation network must be connected

between this pin and the FB2 pin.

CS1 5 I Current sense amplifier input. Connect to the high side of the channel1 current sense resistor.

CS2 20 I Current sense amplifier input. Connect to the high side of the channel2 current sense resistor.

CSG1 4 I Kelvin ground connection to the external current sense resistor. Connect directly to the low side of the

channel1 current sense resistor.

CSG2 21 I Kelvin ground connection to the external current sense resistor. Connect directly to the low side of the

channel2 current sense resistor.

DEMB 17 I

Logic input that enables diode emulation when in the low state. In diode emulation mode, the low-side

MOSFET is latched off for the remainder of the PWM cycle when the buck inductor current reverses

direction (current flow from output to ground). When DEMB is high, diode emulation is disabled allowing

current to flow in either direction through the low-side MOSFET. A 50-kΩpulldown resistor internal to the

LM25119 holds DEMB pin low and enables diode emulation if the pin is left floating.

EN2 11 I If the EN2 pin is low, channel2 is disabled. Channel1 and all other functions remain active. The EN2 has

a 50-kΩpullup resistor to enable channel2 when the pin is left floating.

FB1 9 I Feedback input and inverting input of the channel1 internal error amplifier. A resistor divider from the

channel1 output to this pin sets the output voltage level. The regulation threshold at the FB1 pin is 0.8 V.

FB2 16 I Feedback input and inverting input of the channel2 internal error amplifier. A resistor divider from the

channel2 output to this pin sets the output voltage level. The regulation threshold at the FB2 pin is 0.8 V.

HB1 30 P High-side driver supply for bootstrap gate drive. Connect to the cathode of the channel1 external

bootstrap diode and to the bootstrap capacitor. The bootstrap capacitor supplies current to charge the

high-side MOSFET gate and must be placed as close to controller as possible.

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Pin Functions (continued)

PIN TYPE(1) DESCRIPTION

NAME NO.

HB2 27 P High-side driver supply for bootstrap gate drive. Connect to the cathode of the channel2 external

bootstrap diode and to the bootstrap capacitor. The bootstrap capacitor supplies current to charge the

high-side MOSFET gate and must be placed as close to the controller as possible.

HO1 31 O High-side MOSFET gate drive output. Connect to the gate of the channel1 high-side MOSFET through a

short, low inductance path.

HO2 26 O High-side MOSFET gate drive output. Connect to the gate of the channel2 high-side MOSFET through a

short, low inductance path.

LO1 2 O Low-side MOSFET gate drive output. Connect to the gate of the channel1 low-side synchronous

MOSFET through a short, low inductance path.

LO2 23 O Low-side MOSFET gate drive output. Connect to the gate of the channel2 low-side synchronous

MOSFET through a short, low inductance path.

PGND1 3 G Power ground return pin for low-side MOSFET gate driver. Connect directly to the low side of the

channel1 current sense resistor.

PGND2 22 G Power ground return pin for low-side MOSFET gate driver. Connect directly to the low side of the

channel2 current sense resistor.

RAMP1 6 I PWM ramp signal. An external resistor and capacitor connected between the SW1 pin, the RAMP1 pin

and the AGND pin sets the channel1 PWM ramp slope. Proper selection of component values produces

a RAMP1 signal that emulates the current in the buck inductor.

RAMP2 19 I PWM ramp signal. An external resistor and capacitor connected between the SW2 pin, the RAMP2 pin

and the AGND pin sets the channel2 PWM ramp slope. Proper selection of component values produces

a RAMP2 signal that emulates the current in the buck inductor.

RES 14 O

The restart timer pin for an external capacitor that configures the hiccup mode current limiting. A

capacitor on the RES pin determines the time the controller remains off before automatically restarting in

hiccup mode. The two regulator channels operate independently. One channel may operate in normal

mode while the other is in hiccup mode overload protection. The hiccup mode commences when either

channel experiences 256 consecutive PWM cycles with cycle-by-cycle current limiting. After this occurs, a

10-µA current source charges the RES pin capacitor to the 1.25-V threshold which restarts the

overloaded channel.

RT 13 I The internal oscillator is set with a single resistor between RT and AGND. The recommended maximum

oscillator frequency is 1.5 MHz which corresponds to a maximum switching frequency of 750 kHz for

either channel. The internal oscillator can be synchronized to an external clock by coupling a positive

pulse into RT through a small coupling capacitor.

SS1 7 I An external capacitor and an internal 10-µA current source set the ramp rate of the channel1 error amp

reference. The SS1 pin is held low when VCC1 or VCC2 < 4 V, UVLO < 1.25 V or during thermal

shutdown.

SS2 18 I An external capacitor and an internal 10-µA current source set the ramp rate of the channel2 error amp

reference. The SS2 pin is held low when VCC1 or VCC2 < 4 V, UVLO < 1.25 V or during thermal

shutdown.

SW1 32 I/O Switching node of the buck regulator. Connect to channel1 bootstrap capacitor, the source terminal of the

high-side MOSFET and the drain terminal of the low-side MOSFET.

SW2 25 I/O Switching node of the buck regulator. Connect to channel2 bootstrap capacitor, the source terminal of the

high-side MOSFET and the drain terminal of the low-side MOSFET.

UVLO 28 I

Undervoltage lockout programming pin. If the UVLO pin is below 0.4 V, the regulator is in the shutdown

mode with all function disabled. If the UVLO pin is greater than 0.4 V and below 1.25 V, the regulator is

in standby mode with the VCC regulators operational, the SS pins grounded and no switching at the HO

and LO outputs. If the UVLO pin voltage is above 1.25 V, the SS pins are allowed to ramp and pulse

width modulated gate drive signals are delivered at the LO and HO pins. A 20-µA current source is

enabled when UVLO exceeds 1.25 V and flows through the external UVLO resistors to provide

hysteresis.

VCCDIS 8 I

Optional input that disables the internal VCC regulators when external biasing is supplied. If VCCDIS >

1.25 V, the internal VCC regulators are disabled. The externally supplied bias must be coupled to the

VCC pins through a diode. VCCDIS has a 500-kΩpulldown resistor to ground to enable the VCC

regulators when the pin is left floating. The pulldown resistor can be overridden by pulling VCCDIS above

1.25 V with a resistor divider connected to the external bias supply.

VIN 29 P Supply voltage input source for the VCC regulators.

Thermal Pad — Thermal pad of WQFN package. No internal electrical connections. Solder to the ground plane to reduce

thermal resistance.

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(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings

only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended

Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) These pins must not exceed VIN.

6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)(1)

MIN MAX UNIT

VIN to AGND –0.3 45 V

SW1, SW2 to AGND –3 45 V

HB1 to SW1, HB2 to SW2 –0.3 15 V

VCC1, VCC2 to AGND (2) –0.3 15 V

FB1, FB2, DEMB, RES, VCCDIS, UVLO to AGND –0.3 15 V

HO1 to SW1, HO2 to SW2 –0.3 VHB + 0.3 V

LO1, LO2 to AGND –0.3 VVCC + 0.3 V

SS1, SS2 to AGND –0.3 7 V

EN2, RT to AGND –0.3 7 V

CS1, CS2, CSG1, CSG2 to AGND –0.3 0.3 V

PGND to AGND –0.3 0.3 V

Junction temperature, TJ150 °C

Storage temperature, Tstg –55 150 °C

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

(2) The human-body model is a 100-pF capacitor discharged through a 1.5-kΩresistor into each pin.

(3) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

6.2 ESD Ratings VALUE UNIT

V(ESD) Electrostatic

discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1)(2) ±2000 V

Charged-device model (CDM), per JEDEC specification JESD22-C101(3) ±750

(1) COMP1, COMP2, RAMP1, and RAMP2 are output pins. As such they are not specified to have an external voltage applied.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)(1)

MIN MAX UNIT

VIN 4.5 42 V

VCC 4.5 14 V

HB to SW 4.5 14 V

TJJunction temperature –40 125 °C

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(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application

report, SPRA953.

6.4 Thermal Information

THERMAL METRIC(1) LM25119

UNITRTV (WQFN)

32 PINS

RθJA Junction-to-ambient thermal resistance 36.7 °C/W

RθJC(top) Junction-to-case (top) thermal resistance 20.9 °C/W

RθJB Junction-to-board thermal resistance 9 °C/W

ψJT Junction-to-top characterization parameter 0.2 °C/W

ψJB Junction-to-board characterization parameter 8.9 °C/W

RθJC(bot) Junction-to-case (bottom) thermal resistance 2.2 °C/W

(1) Minimum and maximum limits are 100% production tested at 25°C. Limits over the operating temperature range are specified through

correlation using Statistical Quality Control (SQC) methods. Limits are used to calculate Texas Instrument's Average Outgoing Quality

Level (AOQL).

(2) Per VCC Regulator.

6.5 Electrical Characteristics

Typical values correspond to TJ= 25°C. Minimum and maximum limits apply over –40°C to 125°C junction temperature

range. VIN = 36 V, VCC = 8 V, VCCDIS = 0 V, EN2 = 5 V, RT= 25 kΩ, and no load on LO or HO (unless otherwise noted).

PARAMETER TEST CONDITIONS MIN(1) TYP MAX(1) UNIT

VIN SUPPLY

IBIAS VIN operating current VSS1 = VSS2 = 0 V 6 7.3 mA

VVCCDIS = 2 V, VSS1 = VSS2 = 0 V 340 500 µA

IVCC VCC1 operating current VVCCDIS = 2 V, VSS1 = VSS2 = 0 V 3.9 4.5 mA

VCC2 operating current VVCCDIS = 2 V, VSS1 = VSS2 = 0 V 1.4 2 mA

ISHUTDOWN VIN shutdown current VUVLO = 0 V, VSS1 = VSS2 = 0 V 15 33 µA

VCC REGULATOR(2)

VCC(REG) VCC regulation 6.77 7.6 8.34 V

VIN = 4.5 V, No external load 4.4 4.46

Sourcing current limit VCC = 0 V 25 40 mA

VCCDIS switch threshold VVCCDIS rising 1.19 1.25 1.29 V

VCCDIS switch hysteresis 0.07 V

VCCDIS input current VVCCDIS = 0 V –20 nA

Undervoltage threshold Positive going VCC 3.8 4 4.2 V

Undervoltage hysteresis 0.2 V

EN2 INPUT

VIL EN2 input low threshold 2 1.5 V

VIH EN2 input high threshold 2.9 2.5 V

EN2 input pullup resistor 50 kΩ

UVLO

Threshold UVLO rising 1.2 1.25 1.29 V

Hysterisis current VUVLO = 1.4 V 15 20 25 µA

Shutdown threshold 0.4 V

Shutdown hysteresis voltage 0.1 V

SOFT START

Current source VSS = 0 V 7 10 13 µA

Pulldown RDSON 10 Ω

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Electrical Characteristics (continued)

Typical values correspond to TJ= 25°C. Minimum and maximum limits apply over –40°C to 125°C junction temperature

range. VIN = 36 V, VCC = 8 V, VCCDIS = 0 V, EN2 = 5 V, RT= 25 kΩ, and no load on LO or HO (unless otherwise noted).

PARAMETER TEST CONDITIONS MIN(1) TYP MAX(1) UNIT

ERROR AMPLIFIER

VREF FB reference voltage Measured at FB pin, FB = COMP 0.788 0.8 0.812 V

FB input bias current VFB = 0.8 V 1 nA

FB disable threshold Interleaved threshold 2.5 V

COMP VOH ISOURCE = 3 mA 2.8 V

COMP VOL ISINK = 3 mA 0.31 V

AOL DC gain 80 dB

fBW Unity gain bandwidth 3 MHz

PWM COMPARATORS

tHO(OFF) Forced HO OFF-time 220 320 430 ns

tON(min) Minimum HO ON-time CRAMP = 50 pF 100 ns

OSCILLATOR

fSW1 Frequency 1 RT= 25 kΩ180 200 220 kHz

fSW2 Frequency 2 RT= 10 kΩ430 480 530 kHz

RT output voltage 1.25 V

RT sync positive threshold TJ= 25°C 2.5 3.2 4 V

Sync pulse minimum width 100 ns

CURRENT LIMIT

VCS(TH) Cycle-by-cycle sense voltage

threshold (CS – CSG) RAMP = 0 106 120 134 mV

CS bias current VCS = 0 V –70 –95 µA

Hiccup mode fault timer 256 Cycles

RES

IRES Current source 9.7 µA

VRES Threshold CRES charging 1.2 1.25 1.3 V

DIODE EMULATION

VIL DEMB input low threshold 2 1.65 V

VIH DEMB input high threshold 2.9 2.6 V

DEMB input pulldown resistance 50 kΩ

SW zero cross threshold –5 mV

LO GATE DRIVER

VOLL LO low-state output voltage ILO = 100 mA 0.1 0.18 V

VOHL LO high-state output voltage ILO = –100 mA, VOHL = VCC – VLO 0.17 0.26 V

LO rise time CLOAD = 1000 pF 6 ns

LO fall time CLOAD = 1000 pF 5 ns

IOHL Peak LO source current VLO = 0 V 2.5 A

IOLL Peak LO sink current VLO = VCC 3.3 A

HO GATE DRIVER

VOLH HO low-state output voltage IHO = 100 mA 0.11 0.19 V

VOHH HO high-state output voltage IHO = –100 mA, VOHH = VHB – VHO 0.18 0.27 V

HO rise time CLOAD = 1000 pF 6 ns

HO fall time CLOAD = 1000 pF 5 ns

IOHH Peak HO Source current VHO = 0 V, VSW = 0, VHB = 8 V 2.2 A

IOLH Peak HO sink current VHO = VHB = 8 V 3.3 A

HB to SW undervoltage 3 V

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Electrical Characteristics (continued)

Typical values correspond to TJ= 25°C. Minimum and maximum limits apply over –40°C to 125°C junction temperature

range. VIN = 36 V, VCC = 8 V, VCCDIS = 0 V, EN2 = 5 V, RT= 25 kΩ, and no load on LO or HO (unless otherwise noted).

PARAMETER TEST CONDITIONS MIN(1) TYP MAX(1) UNIT

HB DC bias current VHB – VSW = 8 V 70 100 µA

THERMAL

TSD Thermal shutdown Rising 165 °C

Thermal shutdown hysteresis 25 °C

6.6 Switching Characteristics

Typical values correspond to TJ= 25°C. Minimum and maximum limits apply over –40°C to 125°C junction temperature

range. VIN = 36 V, VCC = 8 V, VVCCDIS = 0 V, VEN2 = 5 V, RT= 25 kΩ, and no load on LO or HO (unless otherwise noted).

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

LO fall to HO rise delay No load 70 ns

HO fall to LO rise delay No load 60 ns

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6.7 Typical Characteristics

Figure 1. HO Peak Driver Current vs Output Voltage Figure 2. LO Peak Driver Current vs Output Voltage

Figure 3. Driver Dead Time vs VCC Figure 4. Driver Dead Time vs Temperature

Figure 5. VCC vs IVCC Figure 6. Switching Frequency vs RT

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Typical Characteristics (continued)

Figure 7. Error Amp Gain and Phase vs Frequency

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7 Detailed Description

7.1 Overview

The LM25119 high voltage switching regulator features all of the functions necessary to implement an efficient

dual-channel buck regulator that operates over a very wide input voltage range. The LM25119 may be configured

as two independent regulators or as a single high-current regulator with two interleaved channels. This easy-to-

use regulator integrates high-side and low-side MOSFET drivers capable of supplying peak currents of 2.5 A

(VCC = 8 V). The regulator control method is based on current mode control using an emulated current ramp.

Emulated peak current mode control provides inherent line feedforward, cycle-by-cycle current limiting and ease-

of-loop compensation. The use of an emulated control ramp reduces noise sensitivity of the pulse-width

modulation circuit, allowing reliable processing of the very small duty cycles necessary in high input voltage

applications. The switching frequency is user programmable from 50 kHz to 750 kHz. An oscillator or

synchronization pin allows the operating frequency to be set by a single resistor or synchronized to an external

clock. An undervoltage lockout and channel2 enable pin allows either both regulators to be disabled or channel2

to be disabled with full operation of channel1. Fault protection features include current limiting, thermal shutdown

and remote shutdown capability. The undervoltage lockout input enables both channels when the input voltage

reaches a user selected threshold and provides a very low quiescent shutdown current when pulled low. The

32-pin WQFN package features an exposed pad to aid in thermal dissipation.

VIN

RES

UVLO

VCC2

FB2

SS2

0.8V

HB2

HO2

SW2

DISABLE

LO2

VCC2

DRIVER

CS2

A = 10

CLK 2

RAMP2

PGND2

COMP2

CSG2

EN2

AGND

VCC DISABLE

LOGIC

CHANNEL 2

UVLO

LEVEL SHIFT/

ADAPTIVE

TIMER

TRACK

SAMPLE

and

HOLD

EN2

LOGIC

CLK 2

1.2V

10 PA

VCC

UVLO

7.6V

REGULATOR

VIN

1.2V

VCC1

FB1

SS1

0.8V

HB1

HO1

SW1

DISABLE

LO1

VCC1

DRIVER

CS1

A = 10

CLK 1

RAMP1

PGND1

COMP1

CSG1

LOGIC DECODER/

DIODE EMULATION

UVLO

LEVEL SHIFT/

ADAPTIVE

TIMER

TRACK

SAMPLE

and

HOLD

CLK 1

1.2V

10 PA

VCC

UVLO

7.6V

REGULATOR

VIN

1.2V

CHANNEL 1

COMMON BIAS

GENERATOR

BIAS

0.8V

UVLO

LOGIC SHUTDOWN

STANDBY

CONTROL

THERMAL

SHUTDOWN

CHANNEL 1

CHANNEL 2

50 k:

VCCDIS

DEMB

VCC DISABLE

LOGIC

VCC

REGULATORS

LOGIC

DECODER

CHANNEL 1

CHANNEL 2

500 k:

50 k:

OSCILLATOR /

SYNC DETECTOR

CLK 1

CLK 2

10 PARESTART

LOGIC

HICCUP

FAULT TIMER

256 CYCLES

CHANNEL 1

STANDBY CHANNEL 2

STANDBY

CHANNEL 1

FAULT CHANNEL 2

FAULT

COMMON

LOGIC DECODER/

DIODE EMULATION

VCC DISABLE

LOGIC

RES Current

SS1 Current

SS2 Current

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7.2 Functional Block Diagram

COUT

VCC

VOUT

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7.3 Feature Description

7.3.1 High Voltage Start-Up Regulator

The LM25119 contains two internal high voltage bias regulators, VCC1 and VCC2, that provide the bias supply

for the PWM controllers and gate drive for the MOSFETs of each regulator channel. The input pin (VIN) can be

connected directly to an input voltage source as high as 42 V. The outputs of the VCC regulators are set to

7.6 V. When the input voltage is below the VCC set-point level, the VCC output tracks the VIN with a small

dropout voltage. If VCC1 is in an undervoltage condition, channel2 is disabled. This interdependence is

necessary to prevent channel2 from running open-loop in the single output interleaved mode when the channel2

error amplifier is disabled (if either VCC is in UV, both channels are disabled).

The outputs of the VCC regulators are current limited at 25-mA (minimum) output capability. Upon power up, the

regulators source current into the capacitors connected to the VCC pins. When the voltage at the VCC pins

exceed 4 V and the UVLO pin is greater than 1.25 V, both channels are enabled and a soft-start sequence

begins. Both channels remain enabled until either VCC pin falls below 3.8 V, the UVLO pin falls below 1.25 V or

the die temperature exceeds the thermal limit threshold.

When operating at higher input voltages the bias power dissipation within the controller can be excessive. An

output voltage derived bias supply can be applied to a VCC pins to reduce the IC power dissipation. The

VCCDIS input can be used to disable the internal VCC regulators when external biasing is supplied.

If VCCDIS > 1.25 V, the internal VCC regulators are disabled. The externally supplied bias must be coupled to

the VCC pins through a diode, preferably a Schottky (low forward voltage). VCCDIS has a 500-kΩinternal

pulldown resistance to ground for normal operation with no external bias. The internal pulldown resistance can

be overridden by pulling VCCDIS above 1.25 V through a resistor divider connected to an external bias supply.

The VCC regulator series pass transistor includes a diode between VCC and VIN that must not be forward-

biased in normal operation.

If the external bias winding can supply VCC greater than VIN, an external blocking diode is required from the

input power supply to the VIN pin to prevent the external bias supply from passing current to the input supply

through the VCC pins. For VOUT between 5 V and 14.5 V, VOUT can be connected directly to VCC through a

diode. For VOUT < 5 V, a bias winding on the output inductor can be added as shown in Figure 8.

Figure 8. VCC Bias Supply With Additional Inductor Winding

In high voltage applications, take extra care to ensure the VIN pin does not exceed the absolute maximum

voltage rating of 45 V. During line or load transients, voltage ringing on the VIN line that exceeds the absolute

maximum rating can damage the IC. Both careful PCB layout and the use of quality bypass capacitors located

close to the VIN and AGND pins are essential.

7.3.2 UVLO

The LM25119 contains a dual-level undervoltage lockout (UVLO) circuit. When the UVLO pin is less than 0.4 V,

the LM25119 is in shutdown mode. The shutdown comparator provides 100 mV of hysteresis to avoid chatter

during transitions. When the UVLO pin voltage is greater than 0.4 V but less than 1.25 V, the controller is in

standby mode. In the standby mode the VCC bias regulators are active but the controller outputs are disabled.

This feature allows the UVLO pin to be used as a remote enable or disable function. When the VCC outputs

exceed their respective undervoltage thresholds (4 V) and the UVLO pin voltage is greater than 1.25 V, the

outputs are enabled and normal operation begins.

TSW

5.2 10

R 948

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Feature Description (continued)

An external set-point voltage divider from the VIN to GND is used to set the minimum VIN operating voltage of

the regulator. The divider must be designed such that the voltage at the UVLO pin is greater than 1.25 V when

the input voltage is in the desired operating range. UVLO hysteresis is accomplished with an internal 20-μA

current source that is switched on or off into the impedance of the set-point divider. When the UVLO pin voltage

exceeds 1.25-V threshold, the current source is activated to quickly raise the voltage at the UVLO pin. When the

UVLO pin voltage falls below the 1.25-V threshold, the current source is turned off causing the voltage at the

UVLO pin to quickly fall. The UVLO pin must not be left floating.

7.3.3 Enable 2

The LM25119 contains an enable function allowing shutdown control of channel2, independent of channel1. If

the EN2 pin is pulled below 2 V, channel2 enters shutdown mode. If the EN2 input is greater than 2.5 V,

channel2 returns to normal operation. An internal 50-kΩpullup resistor on the EN2 pin allows this pin to be left

floating for normal operation. The EN2 input can be used in conjunction with the UVLO pin to sequence the two

regulator channels. If EN2 is held low as the UVLO pin increases to a voltage greater than the 1.25-V UVLO

threshold, channel1 begins operation while channel2 remains off. Both channels become operational when the

UVLO, EN2, VCC1, and VCC2 pins are above their respective operating thresholds. Either channel of the

LM25119 can also be disabled independently by pulling the corresponding SS pin to AGND.

7.3.4 Oscillator and Sync Capability

The LM25119 switching frequency is set by a single external resistor connected between the RT pin and the

AGND pin (RT). The resistor must be located very close to the device and connected directly to the pins of the IC

(RT and AGND). To set a desired switching frequency (fSW) of each channel, the resistor can be calculated with

Equation 1.

where

• RT is in ohms (Ω)

• fSW is in hertz (Hz) (1)

The frequency fSW is the output switching frequency of each channel. The internal oscillator runs at twice the

switching frequency and an internal frequency divider interleaves the two channels with 180° phase shift between

PWM pulses at the HO pins.

The RT pin can be used to synchronize the internal oscillator to an external clock. The internal oscillator can be

synchronized by AC coupling a positive edge into the RT pin. The voltage at the RT pin is nominally 1.25 V and

the voltage at the RT pin must exceed 4 V to trip the internal synchronization pulse detector. A 5-V amplitude

signal and 100-pF coupling capacitor are recommended. Synchronizing at greater than twice the free-running

frequency may result in abnormal behavior of the pulse width modulator. Also, note that the output switching

frequency of each channel is one-half the applied synchronization frequency.

7.3.5 Error Amplifiers and PWM Comparators

Each of the two internal high-gain error amplifiers generates an error signal proportional to the difference

between the regulated output voltage and an internal precision reference (0.8 V). The output of each error

amplifier is connected to the COMP pin allowing the user to provide loop compensation components. Generally a

Type II network is recommended. This network creates a pole at 0 Hz, a mid-band zero, and a noise-reducing,

high-frequency pole. The PWM comparator compares the emulated current sense signal from the RAMP

generator to the error amplifier output voltage at the COMP pin. Only one error amplifier is required when

configuring the controller as a two channel, single output interleaved regulator. For these applications, the

channel1 error amplifier (FB1, COMP1) is configured as the master error amplifier. The channel2 error amplifier

must be disabled by connecting the FB2 pin to the VCC2 pin. When configured in this manner the output of the

channel2 error amplifier (COMP2) is disabled and have a high output impedance. To complete the interleaved

configuration, the COMP1 and the COMP2 pins must be connected together to facilitate PWM control of

channel2 and current sharing between channels.

IN PERIOD

RAMP RAMP RAMP

V t

VR C

PERIOD

RAMP IN RAMP RAMP

V V 1 eR C

§ ·

u 

¨ ¸

IN S

RAMP 10 K V R

dVdt L

u u u

RAMP

Sample and

Hold DC Level

VIN x tON

10 x RS V/A

tON

RRAMP x CRAMP

RAMP =

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Feature Description (continued)

7.3.6 Ramp Generator

The ramp signal used in the pulse width modulator for current mode control is typically derived directly from the

buck switch current. This switch current corresponds to the positive slope portion of the inductor current. Using

this signal for the PWM ramp simplifies the control loop transfer function to a single pole response and provides

inherent input voltage feedforward compensation. The disadvantage of using the buck switch current signal for

PWM control is the large leading edge spike due to circuit parasitics that must be filtered or blanked. Also, the

current measurement may introduce significant propagation delays. The filtering, blanking time, and propagation

delay limit the minimum achievable pulse width. In applications where the input voltage may be relatively large in

comparison to the output voltage, controlling small pulse widths and duty cycles are necessary for regulation.

The LM25119 uses a unique ramp generator which does not actually measure the buck switch current but rather

reconstructs the signal. Representing or emulating the inductor current provides a ramp signal to the PWM

comparator that is free of leading edge spikes and measurement or filtering delays. The current reconstruction is

comprised of two elements; a sample-and-hold DC level and the emulated inductor current ramp as shown in

Figure 9.

Figure 9. Composition of Current Sense Signal

The sample-and-hold DC level is derived from a measurement of the recirculating current flowing through the

current sense resistor. The voltage across the sense resistor is sampled and held just prior to the onset of the

next conduction interval of the buck switch. The current sensing and sample-and-hold provide the DC level of the

reconstructed current signal. The positive slope inductor current ramp is emulated by an external capacitor

connected from RAMP pin to AGND and a series resistor connected between SW and RAMP. The ramp resistor

must not be connected to VIN directly because the RAMP pin voltage rating could be exceeded under high VIN

conditions. The ramp created by the external resistor and capacitor has a slope proportional to the rising inductor

current plus some additional slope required for slope compensation. Connecting the RAMP pin resistor to SW

provides optimum slope compensation with a RAMP capacitor slope that is proportional to VIN. This adaptive

slope compensation eliminates the requirement for additional slope compensation circuitry with high output

voltage set points and frees the user from additional concerns in this area. The emulated ramp signal is

approximately linear and the ramp slope is given in Equation 2.

(2)

The factor of 10 Equation 2 corresponds to the internal current sense amplifier gain of the LM25119. The K factor

is a constant which adds additional slope for robust pulse-width modulation control at lower input voltages. In

practice this constant can be varied from 1 to 3. RSis the external sense resistor value.

The voltage on the ramp capacitor is given with Equation 3and Equation 4.

(3)

(4)

The approximation is the first order term in a Taylor Series expansion of the exponential and is valid because

tPERIOD is small relative to the RAMP pin R-C time constant.

CURRENT LIMIT

COMPARATOR CS

RAMP

CLK

CSG

1.2V CURRENT SENSE

AMPLIFIER

A=10

CRAMP

RRAMP

RSIL

RAMP S RAMP

C10 R K R

u u u

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Feature Description (continued)

Multiplying Equation 2 by tPERIOD to convert the slope to a peak voltage, and then equating Equation 2 with

Equation 4 allows us to solve for CRAMP using Equation 5.

(5)

Choose either CRAMP or RRAMP and use Equation 5 to calculate the other component.

The difference between the average inductor current and the DC value of the sampled inductor current can

cause instability for certain operating conditions. This instability is known as sub-harmonic oscillation, which

occurs when the inductor ripple current does not return to its initial value by the start of next switching cycle.

Sub-harmonic oscillation is normally characterized by alternating wide and narrow pulses at the switch node. The

ramp equation above contains the optimum amount of slope compensation, however extra slope compensation is

easily added by selecting a lower value for RRAMP or CRAMP.

7.3.7 Current Limit

The LM25119 contains a current limit monitoring scheme to protect the regulator from possible overcurrent

conditions. When set correctly, the emulated current signal is proportional to the buck switch current with a scale

factor determined by the current limit sense resistor, RS, and current sense amplifier gain. The emulated signal is

applied to the current limit comparator. If the emulated ramp signal exceeds 1.2 V, the present cycle is

terminated (cycle-by-cycle current limiting). Shown in Figure 10 is the current limit comparator and a simplified

current measurement schematic. In applications with small output inductance and high input voltage, the switch

current may overshoot due to the propagation delay of the current limit comparator. If an overshoot must occur,

the sample-and-hold circuit detects the excess recirculating current before the buck switch is turned on again. If

the sample-and-hold DC level exceeds the internal current limit threshold, the buck switch is disabled and skip

pulses until the current has decayed below the current limit threshold. This approach prevents current runaway

conditions due to propagation delays or inductor saturation because the inductor current is forced to decay to a

controlled level following any current overshoot.

Figure 10. Current Limit and Ramp Circuit

7.3.8 Hiccup Mode Current Limiting

To further protect the regulator during prolonged current limit conditions, an internal counter counts the PWM

clock cycles during which cycle-by-cycle current limiting occurs. When the counter detects 256 consecutive

cycles of current limiting, the regulator enters a low power dissipation hiccup mode with the HO and LO outputs

disabled. The restart timer pin, RES, and an external capacitor configure the hiccup mode current limiting. A

capacitor on the RES pin (CRES) determines the time the controller remains in low power standby mode before

automatically restarting. A 10-µA current source charges the RES pin capacitor to the 1.25-V threshold which

restarts the overloaded channel. The two regulator channels operate independently. One channel may operate

normally while the other is in the hiccup mode overload protection. The hiccup mode commences when either

channel experiences 256 consecutive PWM cycles with cycle-by-cycle current limiting. If that occurs, the

overloaded channel turns off and remains off for the duration of the RES pin timer.

The hiccup mode current-limiting function can be disabled. The RES configuration is latched during initial power

up when UVLO is above 1.25 V and VCC1 and VCC2 are above their UV thresholds, determining hiccup or non-

hiccup current limiting. If the RES pin is tied to VCC at initial power on, hiccup current limit is disabled.

MAX SW

D f 9

1 320 10-

= - ´ ´

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Feature Description (continued)

7.3.9 Soft Start

The soft-start feature allows the regulator to gradually reach the steady-state operating point, thus reducing start-

up stresses and surges. The LM25119 regulates the FB pin to the SS pin voltage or the internal 0.8-V reference,

whichever is lower. At the beginning of the soft-start sequence when SS = 0 V, the internal 10-µA soft-start

current source gradually increases the voltage on an external soft-start capacitor (CSS) connected to the SS pin

resulting in a gradual rise of the FB and output voltages.

Either regulator channel of the LM25119 can be disabled by pulling the corresponding SS pin to AGND.

7.3.10 HO and LO Output Drivers

The LM25119 contains a high-current, high-side driver and associated high voltage level shift to drive the buck

switch of each regulator channel. This gate driver circuit works in conjunction with an external diode and

bootstrap capacitor. A 0.1 µF or larger ceramic capacitor, connected with short traces between the HB pin and

SW pin, is recommended. During the OFF-time of the high-side MOSFET, the SW pin voltage is approximately 0

V and the bootstrap capacitor charges from VCC through the external bootstrap diode. When operating with a

high PWM duty cycle, the buck switch is forced off each cycle for 320 ns to ensure that the bootstrap capacitor is

recharged.

The LO and HO outputs are controlled with an adaptive dead-time methodology which insures that both outputs

are never enabled at the same time. When the controller commands HO to be enabled, the adaptive dead-time

logic first disables LO and waits for the LO voltage to drop. HO is then enabled after a small delay. Similarly, the

LO turnon is disabled until the HO voltage has discharged. This methodology insures adequate dead-time for any

size MOSFET.

Exercise care in selecting an output MOSFET with the appropriate threshold voltage, especially if VCC is

supplied from the regulator output. During start-up at low input voltages the MOSFET threshold must be lower

than the 4-V VCC undervoltage lockout threshold. Otherwise, there may be insufficient VCC voltage to

completely turn on the MOSFET as VCC undervoltage lockout is released during start-up. If the buck switch

MOSFET gate drive is not sufficient, the regulator may not start or it may hang up momentarily in a high power

dissipation state. This condition can be avoided by selecting a MOSFET with a lower threshold voltage or if VCC

is supplied from an external source higher than the output voltage. If the minimum input voltage programmed by

the UVLO pin resistor divider is above the VCC regulation level, this precaution is of no concern.

7.3.11 Maximum Duty Cycle

When operating with a high PWM duty cycle, the buck switch is forced off each cycle for 320 ns to ensure the

bootstrap capacitor is recharged and to allow time to sample and hold the current in the low-side MOSFET. This

forced OFF-time limits the maximum duty cycle of the controller. When designing a regulator with high switching

frequency and high duty cycle requirements, make sure to check the required maximum duty cycle (including

losses) against the graph shown in Figure 11.

The actual maximum duty cycle varies with the operating frequency in Equation 6.

(6)

Figure 11. Maximum Duty Cycle vs Switching Frequency

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Feature Description (continued)

7.3.12 Thermal Protection

Internal thermal shutdown circuitry is provided to protect the integrated circuit in the event the maximum junction

temperature is exceeded. When activated, typically at 165°C, the controller is forced into a low-power reset state,

disabling the output driver and the VCC bias regulators. This feature is designed to prevent catastrophic failures

from overheating and destroying the device.

7.4 Device Functional Modes

7.4.1 Diode Emulation

A fully synchronous buck regulator implemented with a free-wheel MOSFET rather than a diode has the

capability to sink current from the output in certain conditions such as light load, overvoltage, or prebias start-up.

The LM25119 device provides a diode emulation feature that can be enabled to prevent reverse (drain to source)

current flow in the low-side, free-wheel MOSFET. When configured for diode emulation, the low-side MOSFET is

disabled when reverse current flow is detected. The benefit of this configuration is lower power loss at no load or

light load conditions and the ability to turn on into a prebiased output without discharging the output. The diode

emulation mode allows for start-up into prebiased loads, because it prevents reverse current flow as the soft-start

capacitor charges to the regulation level during start-up. The negative effect of diode emulation is degraded light

load transient response times. Enabling the diode emulation feature is recommended and allows discontinuous

conduction operation. The diode emulation feature is configured with the DEMB pin. To enable diode emulation,

connect the DEMB pin to ground or leave the pin floating. If continuous conduction operation is desired, the

DEMB pin must be tied to either VCC1 or VCC2.

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8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

8.1.1 Miscellaneous Functions

EN2 is left floating which allows channel2 to always remain enabled. If EN2 is pulled below 2 V, channel2 is

disabled.

The DEMB pin is left floating because the design sample uses diode emulation. For fully synchronous

(continuous conduction) operation, connect the DEMB to a voltage greater than 2.6 V.

VCCDIS is left floating to enable the internal VCC regulators. To disable the internal VCC regulators, connect this

pin to a voltage greater than 1.25 V.

8.1.2 Interleaved Two-Phase Operation

Interleaved operation offers many advantages in single-output, high-current applications. The output power path

is split between two identical channels reducing the current in each channel by one-half. Ripple current reduction

in the output capacitors is reduced significantly because each channel operates 180 degrees out of phase from

the other. Ripple reduction is greatest at 50% duty cycle and decreases as the duty cycle varies away from 50%.

Refer to Figure 12 to estimate the ripple current reduction. Also, the effective ripple in the input and output

capacitors occurs at twice the frequency of a single-channel design due to the combining of the two channels. All

of these factors are advantageous in managing the higher currents and their effects in a high power design.

Figure 12. Cancellation Factor vs Duty Cycle for Output Capacitor

To begin an interleaved design, use the previous equations in this datasheet to first calculate the required value

of components using one-half the current in the output power path. The attenuation factor in Figure 12 is the ratio

of the output capacitor ripple to the inductor ripple versus duty cycle. The inductor ripple used in this calculation

is the ripple in either inductor in a two phase design, not the ripple calculated for a single phase design of the

same output power. It can be observed that operation around 50% duty cycle results in almost complete ripple

attenuation in the output capacitor. Figure 12 can be used to calculate the amount of ripple attenuation in the

output capacitors.

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Application Information (continued)

Figure 13. Normalized Input Capacitor RMS Ripple Current vs Duty Cycle

Figure 13 illustrates the ripple current reduction in the input capacitors due to interleaving. As with the output

capacitors, there is near perfect ripple reduction near 50% duty cycle. This plot can be used to calculate the

ripple in the input capacitors at any duty cycle. In designs with large duty cycle swings, use the worst-case ripple

reduction for the design.

To configure the LM25119 device for interleaved operation, connect COMP1 and COMP2 pins together at the IC.

Connecting the FB2 pin to VCC2 pin disables the channel2 error amplifier with a high output impedance at

COMP2. Connect the compensation network between FB1 and the common COMP pins. Connect the two power

stages together at the output capacitors. Finally use the plots in Figure 12 and Figure 13 along with the duty

cycle range to determine the amount of output and input capacitor ripple reduction. Frequently more capacitance

than necessary is used in a design just to meet ESR requirements. Reducing the capacitance based solely on

ripple reduction graphs alone may violate this requirement.

8.1.3 Interleaved 4-Phase Operation

Two LM25119 devices can be designed for 4-phase operation with below configurations. The VCC shutdown and

thermal shutdown on master device will shut down all four channels eventually by pulling down COMP bus. The

VCC shutdown and thermal shutdown on slave device will only shut down the device under fault.

• To synchronize two devices and achieve phase shift, a 90 degree shifted clock should be applied to RT pins

of master and slave devices

• Connect COMP pins of master and slave channels together.

• Connect FB pin of slave channel to local VCC pin.

• Connect RES pin to local VCC pin. This means hiccup model should be disabled.

• Connect all UVLO pins of master and slave channels together. This means the UVLO hysteresis current will

be 4 times of 20-μA.

8.2 Typical Applications

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8.2.1 Dual-output Design Example

Figure 14. 3.3-V 8-A, 1.8-V 8-A Dual-Output Application

OUT OUT

PP SW IN(MAX)

V V

L 1

I f V

§ ·

u 

¨ ¸

u© ¹

IPP

0T = 1

fSW

TSW

5.2 10

R 948 21.66 k

 :

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8.2.1.1 Design Requirements

8.2.1.1.1 External Components

The procedure for calculating the external components is illustrated with the following design example. Only the

values for the 3.3 V output are calculated because the procedure is the same for the 1.8-V output. The circuit

shown in Figure 14 is configured for the following specifications:

• CH1 output voltage, VOUT1 = 3.3 V

• CH2 output voltage, VOUT2 = 1.8 V

• CH1 maximum load current, IOUT1 =8A

• CH2 maximum load current, IOUT2 =8A

• Minimum input voltage, VIN(min) =6V

• Maximum input voltage, VIN(max) = 36 V

• Switching frequency, fSW = 230 kHz

Some component values were chosen as a compromise between the 3.3-V and 1.8-V outputs to allow identical

components to be used on both outputs. This design can be reconfigured in a dual-channel interleaved

configuration with a single 3.3-V output which requires identical power channels.

8.2.1.2 Detailed Design Procedure

8.2.1.2.1 Timing Resistor

RTsets the switching frequency of each regulator channel. Generally, higher frequency applications are smaller

but have higher losses. Operation at 230 kHz was selected for this example as a reasonable compromise

between small size and high efficiency. The value of RTfor 230-kHz switching frequency is calculated with

Equation 7.

(7)

A standard value or 22.1 kΩwas chosen for RT. The internal oscillator frequency is twice the switching frequency

and is about 460 kHz.

8.2.1.2.2 Output Inductor

The inductor value is determined based on the operating frequency, load current, ripple current, and the input

and output voltages.

Figure 15. Inductor Current

Knowing the switching frequency, maximum ripple current (IPP), maximum input voltage and the nominal output

voltage (VOUT), the inductor value is calculated with Equation 8.

(8)

RS 3.3 V

P 1 8 0.008 0.46W

36 V

§ ·

 u u

¨ ¸

OUT

RS OUT S

IN(MAX)

P 1 I R

§ ·



¨ ¸

S0.12

R 0.0076

3.3 V 3 1.92A

10.4A 230 kHz 6.8 H 2

 

u P

CS(TH)

SPP

OUT

OUT(MAX) SW

V K

If L 2

 

S RAMP RAMP

K10 R R C

u u u

PP 3.3 V 3.3 V

I 1 1.92A

6.8 H 230 kHz 36 V

§ ·

u 

¨ ¸

P u © ¹

OUT OUT

PP SW IN(MAX)

V V

I 1

L f V

§ ·

u 

¨ ¸

u© ¹

3.3 V 3.3 V

L 1 6.5 H

0.25 8A 230 kHz 36 V

§ ·

u  P

¨ ¸

u u © ¹

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The maximum ripple current occurs at the maximum input voltage. Typically, IPP is 20% to 40% of the full load

current. When operating in the diode emulation mode configuration, the maximum ripple current must be less

than twice the minimum load current. For full synchronous operation, higher ripple current is acceptable. Higher

ripple current allows for a smaller inductor size, but places more of a burden on the output capacitor to smooth

the ripple current. For this example in Equation 9, a ripple current of 25% of 8 A was chosen as a compromise

for the 1.8-V output.

(9)

The nearest standard value of 6.8 μH was chosen for L. Using the value of 6.8 µH for L in Equation 10 and the

example (Equation 11), calculate IPP again. This step is necessary if the chosen value of L differs significantly

from the calculated value.

(10)

(11)

8.2.1.2.3 Current Sense Resistor

Before determining the value of current sense resistor (RS), it is valuable to understand the K factor, which is the

ramp slope multiple chosen for slope compensation. The K factor can vary from 1 to 3 in practice and is defined

with Equation 12.

(12)

The performance of the converter varies depending on the selected K value (see Table 1). For this example, 3

was chosen as the K factor to minimize the power loss in sense resistor RSand the cross-talk between channels.

Crosstalk between the two regulators under certain conditions is observed on the output as switch jitter.

The maximum output current capability (IOUT(MAX)) must be about 20% to 50% higher than the required output

current, (8 A at VOUT1) to account for tolerances and ripple current. For this example, 130% of 8 A was chosen

(10.4 A). The current sense resistor value is calculated with Equation 13 and the example (Equation 14).

where

• VCS(TH) is the current limit threshold voltage (120 mV) (13)

(14)

A value of 8 mΩwas chosen for RS. The sense resistor must be rated to handle the power dissipation at

maximum input voltage when current flows through the free-wheel MOSFET for the majority of the PWM cycle.

The maximum power dissipation of RSis calculated with Equation 15 and the example (Equation 16).

(15)

(16)

During output short condition, the worst-case peak inductor current is limited to Equation 17 and the example

(Equation 18).

OUT

V 19.3 mV'

OUT 1

V 1.92A 0.01 8 230 kHz 680 F

§ ·

' u :  ¨ ¸

u u P

OUT PP SW OUT

V I ESR  ¦ &

§ ·

' u  ¨ ¸

u u

RAMP 6.8 H

R 34.5 k

10 0.008 3 820 pF

u : u u

RAMP S RAMP

R10 R K C

u u u

LIM_PEAK 0.12 36 V 100 ns

I 15.53A

0.008 6.8 H



: P

CS(TH) IN(MAX) ON(MIN)

LIM_PEAK S

V V t

IR L



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where

• tON(MIN) is the minimum HO on-time which is nominally 100 ns (17)

(18)

The chosen inductor must be evaluated for this condition, especially at elevated temperature where the

saturation current rating of the inductor may drop significantly. At the maximum input voltage with a shorted

output, the valley current must fall below VCS(TH) / RSbefore the high-side MOSFET is allowed to turn on.

8.2.1.2.4 Ramp Resistor and Ramp Capacitor

The value of ramp capacitor (CRAMP) must be less than 2 nF to allow full discharge between cycles by the

discharge switch internal to the LM25119 device . A good-quality, thermally-stable ceramic capacitor with 5% or

less tolerance is recommended. For this design the value of CRAMP was set at the standard capacitor value of

820 pF. With the inductor, sense resistor and the K factor selected, the value of the ramp resistor (RRAMP) is

calculated with Equation 19 and the example (Equation 20). The standard value of 34 kΩwas selected.

(19)

(20)

8.2.1.2.5 Output Capacitors

The output capacitors smooth the inductor ripple current and provide a source of charge during transient loading

conditions. For this design example, a 680-µF electrolytic capacitor with 10-mΩESR was selected as the main

output capacitor. The fundamental component of the output ripple voltage is approximated with Equation 21 and

the example (Equation 22 and Equation 23).

(21)

(22)

(23)

Two 22-µF low ERS or ESL ceramic capacitors are placed in parallel with the 680-µF electrolytic capacitor, to

further reduce the output voltage ripple and spikes.

Table 1. Performance Variation by K Factor

K < 1 1 <— K —> 3 K > 3

Cross talk

Sub-harmonic

oscillation may occur

Higher Lower Introduces additional

pole near cross-over

frequency

Peak inductor current with short output condition Lower Higher

Inductor size Smaller Larger

Power dissipation of Rs Higher Lower

Efficiency Lower Higher

S IN

R ESR

2 Z Z

§ ·



G u 

¨ ¸

IN OUT

SIN IN

f2 L C

S u

SIN

IN 8A

V 0.565 V

4 230 kHz 15.4 F

u u P

OUT

IN SW IN

V ¦ &

u u

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8.2.1.2.6 Input Capacitors

The regulator input supply voltage typically has high source impedance at the switching frequency. Good-quality

input capacitors are necessary to limit the ripple voltage at the VIN pin while supplying most of the switch current

during the ON-time. When the buck switch turns on, the current into the buck switch steps to the valley of the

inductor current waveform, ramps up to the peak value, and then drops to the zero at turnoff. The input

capacitance must be selected for RMS current rating and minimum ripple voltage. A good approximation for the

required ripple current rating necessary is IRMS > IOUT / 2. Seven 2.2-μF ceramic capacitors were used for each

channel. With ceramic capacitors, the input ripple voltage is triangular. The input ripple voltage with one channel

operating is approximately Equation 24 and the example (Equation 25).

(24)

(25)

The ripple voltage of the input capacitors is reduced significantly with dual-channel operation because each

channel operates 180 degrees out of phase from the other. Capacitors connected in parallel must be evaluated

for RMS current rating. The current splits between the input capacitors based on the relative impedance of the

capacitors at the switching frequency.

When the converter is connected to an input power source, a resonant circuit is formed by the line inductance

and the input capacitors. To minimize overshoot make CIN > 10 x LIN. The characteristic source impedance (ZS)

and resonant frequency (fS) are Equation 26 and the example (Equation 27).

where

• LIN is the inductance of the input wire (26)

(27)

The converter exhibits negative input impedance which is lowest at the minimum input voltage in Equation 28.

(28)

The damping factor for the input filter is given by Equation 29.

where

• RIN is the input wiring resistance

• ESR is the equivalent series resistance of the input capacitors (29)

When δ= 1, the input filter is critically damped. This may be difficult to achieve with practical component values.

With δ< 0.2, the input filter exhibits significant ringing. If δis zero or negative, there is not enough resistance in

the circuit and the input filter sustains an oscillation. When operating near the minimum input voltage, a bulk

aluminum electrolytic capacitor across CIN may be needed to damp the input for a typical bench test setup.

8.2.1.2.7 VCC Capacitor

The primary purpose of the VCC capacitor (CVCC) is to supply the peak transient currents of the LO driver and

bootstrap diode as well as provide stability for the VCC regulator. These peak currents can be several amperes.

TI recommends the value of CVCC must be no smaller than 0.47 µF, and be a good-quality, low-ESR, ceramic

capacitor located at the pins of the IC to minimize potentially damaging voltage transients caused by trace

inductance. A value of 1 μF was selected for this design.

0.8 V

COMP RCOMP CCOMP

CHF

RFB2

RFB1

VOUT

OUT

FB2

FB1

R 0.8 V



RES

RES 10 A t

C1.25 V

P u

SS t 10 A

C0.8 V

u P

HB HB

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8.2.1.2.8 Bootstrap Capacitor

The bootstrap capacitor between the HB and SW pins supplies the gate current to charge the high-side MOSFET

gate at each cycle’s turnon and recovery charge for the bootstrap diode. These current peaks can be several

amperes. TI recommends the value of the bootstrap capacitor is at least 0.1 μF, and be a good-quality, low-ESR,

ceramic capacitor located at the pins of the IC to minimize potentially damaging voltage transients caused by

trace inductance. The absolute minimum value for the bootstrap capacitor is calculated with Equation 30. A value

of 0.47 μF was selected for this design.

where

• Qgis the high-side MOSFET gate charge

•ΔVHB is the tolerable voltage droop on CHB (which is typically less than 5% of VCC) (30)

8.2.1.2.9 Soft Start Capacitor

The capacitor at the SS pin (CSS) determines the soft-start time (tSS), which is the time for the output voltage to

reach the final regulated value. The value of CSS for a given time is determined from Equation 31. For this

application, a value of 0.047 μF was chosen for a soft-start time of 3.8 ms.

(31)

8.2.1.2.10 Restart Capacitor

The restart pin sources 10 µA into the external restart capacitor (CRES). The value of the restart capacitor is given

by Equation 32. For this application, a value of 0.47 µF was chosen for a restart time of 59 ms.

where

• tRES is the time the device remains off before a restart attempt in hiccup mode current limiting (32)

8.2.1.2.11 Output Voltage Divider

RFB1 and RFB2 set the output voltage level, the ratio of these resistors is calculated from Equation 33.

(33)

Choosing a value of 2.21 kΩfor RFB1 results in a RFB2 value of 6.98 kΩfor a VOUT1 of 3.3 V. A reasonable guide

is to select the value of RFB1 in the range between 500 Ωand 10 kΩ. The value of RFB1 must be large enough to

keep the total divider power dissipation small.

Figure 16. Feedback Configuration

GC SW

P n VCC Qg f u u u

DC(LO MOSFET) O DS(ON)

P (1 D) (I R 1.3)

  u u u

DC(HO MOSFET) O DS(ON)

P D (I R 1.3)

 u u u

UVLO

20 µA

CFT

RUV2

VIN

RUV1

Shutdown

Standby

UV2

UV1 IN

1.25 V R

RV 1.25



HYS

UV2 V

R20 A

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8.2.1.2.12 UVLO Divider

The UVLO threshold is internally set to 1.25 V at the UVLO pin. The LM25119 device is enabled when the

system input voltage VIN causes the UVLO pin to exceed the threshold voltage of 1.25 V. When the UVLO pin

voltage is below the threshold, the internal 20-μA current source is disabled. When the UVLO pin voltage

exceeds the

1.25-V threshold, the 20-μA current source is enabled causing the UVLO pin voltage to increase, providing

hysteresis. The values of RUV1 and RUV2 can be determined from Equation 34 and the example (Equation 35).

(34)

(35)

VHYS is the desired UVLO hysteresis at VIN, and VIN in the second equation is the desired UVLO release

(turnon) voltage. For example, if it is desired for the LM25119 device to be enabled when VIN reaches 5.6 V, and

the desired hysteresis is 1.05 V, then RUV2 must be set to 52.5 kΩand RUV1 must be set to 15.1 kΩ. For this

application, RUV2 was selected to be 52.3 kΩand RUV1was selected to be 15 kΩ. The LM25119 device can be

remotely shutdown by taking the UVLO pin below 0.4 V with an external open-collector or open-drain device. The

outputs and the VCC regulator are disabled in shutdown mode. Capacitor CFT provides filtering for the divider. A

value of 100 pF was chosen for CFT. The voltage at the UVLO pin must never exceed 15 V when using the

external set-point divider. It may be necessary to clamp the UVLO pin at high input voltages.

Figure 17. UVLO Configuration

8.2.1.2.13 MOSFET Selection

Selection of the power MOSFETs is governed by the same tradeoffs as switching frequency. Breaking down the

losses in the high-side and low-side MOSFETs is one way to compare the relative efficiencies of different

devices. When using discrete SO-8 MOSFETs, generally the output current capability range is 2 A to 10 A.

Losses in the power MOSFETs can be broken down into conduction loss, gate charging loss, and switching loss.

Conduction loss PDC is approximately Equation 36 and the example (Equation 37).

(36)

where

• D is the duty cycle

• The 1.3 factor accounts for the increase in MOSFET ON-resistance due to heating (37)

Alternatively, the factor of 1.3 can be eliminated and the high temperature ON-resistance of the MOSFET can be

estimated using the RDS(ON) vs Temperature curves in the MOSFET datasheet. Gate charging loss, PGC, results

from the current driving the gate capacitance of the power MOSFETs and is approximated with Equation 38.

where

• Qgrefers to the total gate charge of an individual MOSFET

• n is the number of MOSFETs (38)

P(MOD) LOAD OUT

f(2 R C )

S u u

LOAD

(MOD) S

DC_GAIN (A R )

SW IN O R F SW

P 0.5 V I (t t ) f u u u  u

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Gate charge loss differs from conduction and switching losses in that the actual dissipation occurs in the

LM25119 device and not in the MOSFET itself. Further loss in the device is incurred if the gate driving current is

supplied by the internal linear regulator.

Switching loss occurs during the brief transition period as the MOSFET turns on and off. During the transition

period both current and voltage are present in the channel of the MOSFET. The switching loss can be

approximated with Equation 39.

where

• tRand tFare the rise and fall times of the MOSFET (39)

The rise and fall times are usually mentioned in the MOSFET datasheet or can be empirically observed with an

oscilloscope. Switching loss is calculated for the high-side MOSFET only. Switching loss in the low-side

MOSFET is negligible because the body diode of the low-side MOSFET turns on before the MOSFET itself,

minimizing the voltage from drain to source before turnon. For this example, the maximum drain-to-source

voltage applied to either MOSFET is 36 V. The selected MOSFETs must be able to withstand 36 V plus any

ringing from drain to source, and be able to handle at least the VCC voltage plus any ringing from gate to source.

A good choice of MOSFET for the 36-V input design example is the SI7884. It has an RDS(ON) of 7.5 mΩand total

gate charge of 21 nC. In applications where a high step-down ratio is maintained in normal operation, efficiency

may be optimized by choosing a high-side MOSFET with lower Qg, and low-side MOSFET with lower RDS(ON).

8.2.1.2.14 MOSFET Snubber

A resistor-capacitor snubber network across the low-side MOSFET reduces ringing and spikes at the switching

node. Excessive ringing and spikes can cause erratic operation and couple noise to the output. Selecting the

values for the snubber is best accomplished through empirical methods. First, make sure the lead lengths for the

snubber connections are very short. Start with a resistor value between 5 and 50 Ω. Increasing the value of the

snubber capacitor results in more damping, but higher snubber losses. Select a minimum value for the snubber

capacitor that provides adequate damping of the spikes on the switch waveform at high load. A snubber may not

be necessary with an optimized layout.

8.2.1.2.15 Error Amplifier Compensation

RCOMP, CCOMP, and CHF configure the error amplifier gain characteristics to accomplish a stable voltage loop gain.

One advantage of current mode control is the ability to close the loop with only two feedback components, RCOMP

and CCOMP. The voltage loop gain is the product of the modulator gain and the error amplifier gain. For the 3.3-V

output design example, the modulator is treated as an ideal voltage-to-current converter. The DC modulator gain

of the LM25119 can be modeled with Equation 40.

where

• A is the gain of the current sense amplifier which is 10 in the LM25119 (40)

The dominant low frequency pole of the modulator is determined by the load resistance (RLOAD) and output

capacitance (COUT). The corner frequency of this pole calculated with Equation 41.

(41)

For RLOAD = 3.3 V / 8 A = 0.413 Ωand COUT = 724 μF (effective) then fP(MOD) = 532 Hz

DC Gain(MOD) = 0.413 Ω/(10x8mΩ) = 5.16 = 14.2 dB

For the 3.3-V design example, the modulator gain versus frequency characteristic is shown in Figure 18.

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Figure 18. Modulator Gain and Phase

Components RCOMP and CCOMP configure the error amplifier as a Type II configuration. The DC gain of the

amplifier is 80 dB with a pole at 0 Hz and a zero at fZEA =1/(2πx RCOMP x CCOMP). The error amplifier zero

cancels the modulator pole leaving a single pole response at the crossover frequency of the voltage loop. A

single pole response at the crossover frequency yields a very stable loop with 90 degrees of phase margin. For

the design example, a conservative target loop bandwidth (crossover frequency) of 11 kHz was selected. The

compensation network zero (fZEA) must be selected at least an order of magnitude less than the target crossover

frequency. This constrains the product of RCOMP and CCOMP for a desired compensation network zero 1 / (2 πx

RCOMP x CCOMP) to be about 1.1 kHz. Increasing RCOMP, while proportionally decreasing CCOMP, increases the

error amp gain. Conversely, decreasing RCOMP while proportionally increasing CCOMP, decreases the error amp

gain. For the design example, CCOMP was selected as 6800 pF and RCOMP was selected as 36.5 kΩ. These

values configure the compensation network zero at 640 Hz. The error amp gain at frequencies greater than fZEA

is: RCOMP / RFB2, which is approximately 5.22 (14.3 dB).

The overall voltage loop gain can be predicted as the sum (in dB) of the modulator gain and the error amp gain.

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Figure 19. Error Amplifier Gain and Phase Figure 20. Overall Voltage Loop Gain and Phase

If a network analyzer is available, the modulator gain can be measured and the error amplifier gain can be

configured for the desired loop transfer function. If the K factor is between 2 and 3, the stability must be checked

with the network analyzer. If a network analyzer is not available, the error amplifier compensation components

can be designed with the guidelines given. Step load transient tests can be performed to verify acceptable

performance. The step load goal is minimum overshoot with a damped response. CHF can be added to the

compensation network to decrease noise susceptibility of the error amplifier. The value of CHF must be

sufficiently small because the addition of this capacitor adds a pole in the error amplifier transfer function. This

pole must be well beyond the loop crossover frequency.

Equation 42 offers a good approximation of the location of the pole added by CHF.

fP2 = fZEA × CCOMP / CHF (42)

The value of CHF was selected as 100 pF for the design example.

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8.2.1.3 Application Curves

VIN = 24 Vdc IOUT rising from 2 A to 6 A

Top trace: VOUT = 3.3 V, 100

mV/div, AC-coupled Bottom trace: IOUT, 2 A/div

Horizontal resolution: 0.5

ms/div

Figure 21. Load Transient Response Figure 22. Typical Efficiency vs Load Current

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8.2.2 Two-Phase Design Example

Figure 23. Two-Phase Design Example

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8.2.2.1 Design Requirements

Below are the design requirements for two-phase operation.

• Output voltage, VOUT = 3.3 V

• Load current, IOUT = 16 A

• Minimum input voltage, VIN(min) =6V

• Maximum input voltage, VIN(max) = 36 V

• Switching frequency, fSW = 230 kHz

8.2.2.2 Detailed Design Procedure

Refer to the design procedure of dual-output example to select external components. In the device evaluation

board (schematic shown in Figure 14) interleaved operation can be enabled by shorting both outputs together

(with identical components in the power train), and using 0-Ωresistors for R22 and R21. This configuration

effectively creates a short circuit between the VCC2 pin and the FB2 pin and between the COMP2 pin and the

COMP1 pin. Also the channel2 feedback network C14, R6, and C15 must be removed.

8.2.2.3 Application Curves

VIN = 12 V VOUT = 3.3 V

IOUT = 16 A

Figure 24. VIN Startup

VIN = 12 V VOUT = 3.3 V

IOUT = 1 A

Figure 25. VIN Shutdown

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VIN = 12 V VOUT = 3.3 V

IOUT = 16 A

Figure 26. Switching

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9 Power Supply Recommendations

LM25119 is a power management device. The power supply for the device is an DC voltage source within the

specified input range.

10 Layout

10.1 Layout Guidelines

The LM25119 consists of two integrated regulators operating almost independently. Crosstalk between the two

regulators under certain conditions may be observed as switch jitter. This effect is common for any dual-channel

regulator. Crosstalk effects are usually most severe when one channel is operating around 50% duty cycle.

Careful layout practices help to minimize this effect. The following board layout guidelines apply specifically to

the device and must be followed for best performance.

• Maintain Loop1 and Loop2, shown in Figure 27, as small as possible

• Maintain separate signal and power grounds

• Place VCC capacitors (C6, C7) and VIN capacitor (C9) as closes as possible to the LM25119 device

• Route CS and CSG traces together with Kelvin connection to the sense resistor

• Connect AGND and PGND directly to the underside exposed pad

• Ensure there are no high current paths beneath the underside exposed pad

10.1.1 Switching Jitter Root Causes and Solutions

• Noise coupling of the high frequency switching between two channels through the input power rail

– Maintain the high current path as short as possible

– Choose a FET with minimum lead inductance

– Place local bypass capacitors (CIN1, CIN2) as close as possible to the high-side FETs to isolate one

channel from the high frequency noise of the other channel

– Slow down the SW switching speed by increasing gate resistors R29 and R30

– Minimize the effective ESR or ESL of the input capacitor by paralleling input capacitors

• High frequency AC noise on FB, CS, CSG and COMP

– Use the star ground PCB layout technique and minimize the length of the high current path

– Place the signal traces away from the SW, HO, HB traces and the inductor

– Add an R-C filter between the CS and CSG pins

– Place CS filter capacitor (C30, C31) next to the LM25119 and on the same PCB layer as the LM25119

• Ground offset at the switching frequency

– Use the star ground PCB layout technique and minimize the length between the grounds of CIN1 and CIN2

VIN

VOUT1

VOUT2

COUT1 COUT2

CIN1 CIN2

PGND2

PGND1

AGND

RFB2A RFB1A RFB1B RFB2B

The bold lines indicate a solid ground plane. Make the traces to the widest and

the shortest and use the star ground technique.

These lines indicate the high current paths. Make the traces as wide and short

as possible

These lines indicate the small signal paths. The traces can be narrow but keep

them away from any radiated noise and away from traces that may couple

noise capacitively

These points require the maximum bypassing of the high frequency switching

noise. Isolate each channel from the high frequency switching noise of the

other channel.

Loop1 Loop2

CS1 CS2

CSG1 CSG2

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10.2 Layout Example

Figure 27. Recommended PCB Layout

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11 Device and Documentation Support

11.1 Community Resources

The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective

contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of

Use.

TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration

among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help

solve problems with fellow engineers.

Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and

contact information for technical support.

11.2 Trademarks

E2E is a trademark of Texas Instruments.

All other trademarks are the property of their respective owners.

11.3 Electrostatic Discharge Caution

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

11.4 Glossary

SLYZ022 —TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.

12 Mechanical, Packaging, and Orderable Information

The following pages include mechanical, packaging, and orderable information. This information is the most

current data available for the designated devices. This data is subject to change without notice and revision of

this document. For browser-based versions of this data sheet, refer to the left-hand navigation.

PACKAGE OPTION ADDENDUM

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Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead finish/

Ball material

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM25119PSQ/NOPB ACTIVE WQFN RTV 32 1000 RoHS & Green SN Level-3-260C-168 HR -40 to 125 L25119P

LM25119PSQE/NOPB ACTIVE WQFN RTV 32 250 RoHS & Green SN Level-3-260C-168 HR -40 to 125 L25119P

LM25119PSQX/NOPB ACTIVE WQFN RTV 32 4500 RoHS & Green SN Level-3-260C-168 HR -40 to 125 L25119P

(1) The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance

do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may

reference these types of products as "Pb-Free".

RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.

Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based

flame retardants must also meet the <=1000ppm threshold requirement.

(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation

of the previous line and the two combined represent the entire Device Marking for that device.

(6) Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two

lines if the finish value exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.

TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

PACKAGE OPTION ADDENDUM

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Addendum-Page 2

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

LM25119PSQ/NOPB WQFN RTV 32 1000 178.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1

LM25119PSQE/NOPB WQFN RTV 32 250 178.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1

LM25119PSQX/NOPB WQFN RTV 32 4500 330.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1

PACKAGE MATERIALS INFORMATION

www.ti.com 30-Apr-2018

Pack Materials-Page 1

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

LM25119PSQ/NOPB WQFN RTV 32 1000 210.0 185.0 35.0

LM25119PSQE/NOPB WQFN RTV 32 250 210.0 185.0 35.0

LM25119PSQX/NOPB WQFN RTV 32 4500 367.0 367.0 35.0

PACKAGE MATERIALS INFORMATION

www.ti.com 30-Apr-2018

Pack Materials-Page 2

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PACKAGE OUTLINE

5.15

4.85

5.15

4.85

0.8

0.7

0.05

0.00

2X 3.5

28X 0.5

2X 3.5

32X 0.5

0.3

32X 0.30

0.18

3.1 0.1

(0.1) TYP

WQFN - 0.8 mm max heightRTV0032A

PLASTIC QUAD FLATPACK - NO LEAD

4224386/B 04/2019

0.08 C

0.1 C A B

0.05

NOTES:

1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing

per ASME Y14.5M.

2. This drawing is subject to change without notice.

3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance.

PIN 1 INDEX AREA

SEATING PLANE

PIN 1 ID

SYMM

EXPOSED

THERMAL PAD

SYMM

916

SCALE 2.500

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EXAMPLE BOARD LAYOUT

28X (0.5)

(1.3)

(R0.05) TYP

0.07 MAX

ALL AROUND

0.07 MIN

ALL AROUND

32X (0.6)

32X (0.24)

(4.8)

(3.1)

( 0.2) TYP

VIA

WQFN - 0.8 mm max heightRTV0032A

PLASTIC QUAD FLATPACK - NO LEAD

4224386/B 04/2019

NOTES: (continued)

4. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature

number SLUA271 (www.ti.com/lit/slua271).

5. Vias are optional depending on application, refer to device data sheet. If any vias are implemented, refer to their locations shown

on this view. It is recommended that vias under paste be filled, plugged or tented.

SYMM

SEE SOLDER MASK

DETAIL

LAND PATTERN EXAMPLE

EXPOSED METAL SHOWN

SCALE: 15X

916

METAL EDGE

SOLDER MASK

OPENING

EXPOSED METAL

METAL UNDER

SOLDER MASK

OPENING

EXPOSED

METAL

NON SOLDER MASK

DEFINED

(PREFERRED) SOLDER MASK DEFINED

SOLDER MASK DETAILS

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EXAMPLE STENCIL DESIGN

32X (0.6)

32X (0.24)

28X (0.5)

(4.8)

(0.775) TYP

4X (1.35)

(R0.05) TYP

WQFN - 0.8 mm max heightRTV0032A

PLASTIC QUAD FLATPACK - NO LEAD

4224386/B 04/2019

NOTES: (continued)

6. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate

design recommendations.

SOLDER PASTE EXAMPLE

BASED ON 0.125 MM THICK STENCIL

SCALE: 20X

EXPOSED PAD 33

76% PRINTED SOLDER COVERAGE BY AREA UNDER PACKAGE

SYMM

916

IMPORTANT NOTICE AND DISCLAIMER

TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCE

DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”

AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY

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