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LP38500-ADJ
,
LP38502-ADJ
SNVS539H –NOVEMBER 2007–REVISED SEPTEMBER 2015
LP3850x-ADJ, LP3850xA-ADJ 1.5-A Flexcap Low-Dropout Linear Regulator
for 2.7-V to 5.5-V Inputs
1 Features 3 Description
TI's FlexCap low-dropout (LDO) linear regulators
1• Input Voltage: 2.7 V to 5.5 V feature unique compensation that allow use of any
• Adjustable Output Voltage: 0.6 V to 5 V type of output capacitor with no limits on minimum or
• FlexCap: Stable with Ceramic, Tantalum, or maximum equivalent series resistance (ESR). The
Aluminum Capacitors LP38500 and LP38502 series of LDOs operates from
a 2.7-V to 5.5-V input supply. These ultra-low-dropout
• Stable with 10-µF Input and Output Capacitors linear regulators respond very quickly to step
• Low Ground-Pin Current changes in load, making them suitable for low-voltage
• 25-nA Quiescent Current in Shutdown Mode microprocessor applications. Developed on a CMOS
process (utilizing a PMOS pass transistor) the
• Ensured Output Current of 1.5 A LP38500-ADJ and LP38502-ADJ have low quiescent
• Ensured VADJ Accuracy of ±1.5% at 25°C (A currents that changes little with load current.
Grade) • GND Pin Current: Typically 2 mA at 1.5-A load
• Ensured Accuracy of ±3.5% at 25°C (STD) current.
• Overtemperature and Overcurrent Protection • Disable Mode: Typically 25-nA quiescent current
• ENABLE Pin (LP38502) when the EN pin is pulled low. (LP38502-ADJ)
• Simplified Compensation: Stable with any type of
2 Applications output capacitor, regardless of ESR.
• Precision Output: Agrade versions available with
• ASIC Power Supplies In: 1.5% VADJ tolerance (25°C) and 3% over line,
– Printers, Graphics Cards, DVD Players load, and temperature.
– Set Top Boxes, Copiers, Routers Device Information(1)
• DSP and FPGA Power Supplies PART NUMBER PACKAGE BODY SIZE (NOM)
• SMPS Regulator DDPAK/TO-263 (5) 10.16 mm x 8.42 mm
• Conversion from 3.3-V or 5-V Rail LP38500 TO-263 (5) 10.16 mm x 9.85 mm
LP38502 WSON (8) 3.00 mm x 2.50 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Typical Circuit (LP38500) Typical Circuit (LP38502)
1
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.
LP38500-ADJ
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SNVS539H –NOVEMBER 2007–REVISED SEPTEMBER 2015
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Table of Contents
7.4 Device Functional Modes........................................ 12
1 Features.................................................................. 18 Application and Implementation ........................ 13
2 Applications ........................................................... 18.1 Application Information............................................ 13
3 Description............................................................. 18.2 Typical Applications ............................................... 13
4 Revision History..................................................... 29 Power Supply Recommendations...................... 16
5 Pin Configurations and Functions....................... 39.1 Power Dissipation/Heatsinking................................ 16
6 Specifications......................................................... 410 Layout................................................................... 17
6.1 Absolute Maximum Ratings ...................................... 410.1 Layout Guidelines ................................................. 17
6.2 ESD Ratings.............................................................. 410.2 Layout Examples................................................... 17
6.3 Recommended Operating Conditions....................... 411 Device and Documentation Support................. 20
6.4 Thermal Information.................................................. 411.1 Documentation Support ........................................ 20
6.5 Electrical Characteristics........................................... 511.2 Community Resources.......................................... 20
6.6 Typical Characteristics.............................................. 711.3 Trademarks........................................................... 20
7 Detailed Description.............................................. 911.4 Electrostatic Discharge Caution............................ 20
7.1 Overview................................................................... 911.5 Glossary................................................................ 20
7.2 Functional Block Diagrams ....................................... 912 Mechanical, Packaging, and Orderable
7.3 Feature Description................................................. 10 Information ........................................................... 20
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision G (June 2015) to Revision H Page
• Changed thermal values for KTT (DDPAK/TO-263); add notes 2 and 3 to Thermal Information table ................................ 4
Changes from Revision F (April 2013) to Revision G Page
• Added Added Device Information and Pin Configuration and Functions sections, ESD Ratings and updated Thermal
Information tables, Feature Description,Device Functional Modes,Application and Implementation,Power Supply
Recommendations,Layout,Device and Documentation Support , and Mechanical, Packaging, and Orderable
Information sections................................................................................................................................................................ 1
• Deleted obsolete heatsinking information for DDPAK/TO-263 package ............................................................................. 16
Changes from Revision E (April 2013) to Revision F Page
• Changed layout of National Data Sheet to TI format ........................................................................................................... 19
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5 Pin Configurations and Functions
KTT Package (LP38500) KTT Package (LP38502)
5-Pin DDPAK/TO-263 5-Pin DDPAK/TO-263
Top View Top View
NDQ Package (LP38500) NDQ Package (LP38502)
5-Pin TO-263 5-Pin TO-263
Top View Top View
NGS Package (LP38500A) NGS Package (LP38502A)
8-Pin WSON 8-Pin WSON
Top View Top View
Pin Functions
PIN TYPE DESCRIPTION
NAME KTT NDQ NGS
ADJ 5 5 8 O Sets output voltage
Enable (LP38502-ADJ only). Pull high to enable the output, low to disable the output.
EN 1 1 2 I This pin has no internal bias and must be either tied to the input voltage, or actively
driven.
GND 3 3 1 G Ground
Input supply (LP38500-ADJ only). Input supply pins share current and must be
IN — — 2 I connected together on the PC board.
Input supply. Input Supply pins share current and must be connected together on the
IN 2 2 3, 4 I PC board.
In the LP38500-ADJ, this pin has no internal connections. It can be left floating or used
N/C 1 1 — — for trace routing.
Regulated output voltage. Output pins share current and must be connected together on
OUT 4 4 5, 6, 7 O the PC board.
The DAP is used to remove heat from the device by conducting it to a copper clad area
on the PCB which acts as a heatsink. The DAP is electrically connected to the backside
DAP √ √ √ —of the die. The DAP must be connected to ground potential, but can not be used as the
only ground connection.
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)(1)(2)
MIN MAX UNIT
Input pin voltage (survival) −0.3 6 V
Enable pin voltage (survival) −0.3 6 V
Output pin voltage (survival) −0.3 6 V
IOUT (survival) Internally limited
Power dissipation(3) Internally limited
Storage temperature, Tstg −65 150 °C
(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) If Military/Aerospace specified devices are required, please contact the Texas Instruments Office/ Distributors for availability and
specifications.
(3) Operating junction temperature must be evaluated, and derated as needed, based on ambient temperature (TA), power dissipation (PD),
maximum allowable operating junction temperature (TJ(MAX)), and package thermal resistance (RθJA). See Application and
Implementation.
6.2 ESD Ratings VALUE UNIT
VESD Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins(1) ±2000 V
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. have higher
performance.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)(1)
MIN NOM MAX UNIT
Input supply voltage 2.7 5.5 V
Enable input voltage 0 5.5 V
Output current (DC) 0 1.5 A
VOUT 0.6 5 V
Junction temperature(1) −40 125 °C
(1) Operating junction temperature must be evaluated, and derated as needed, based on ambient temperature (TA), power dissipation (PD),
maximum allowable operating junction temperature (TJ(MAX)), and package thermal resistance (RθJA). See Application and
Implementation.
6.4 Thermal Information LP38500 and LP38502
THERMAL METRIC(1) KTT(DDPAK/TO-263) NDQ (TO-263) NGS (WSON) UNIT
5 PINS 5 PINS 8 PINS
RθJA(2) Junction-to-ambient thermal resistance 41.8 33.3 52.5(3) °C/W
RθJC(top) Junction-to-case (top) thermal resistance 45.0 22.1 53.6 °C/W
RθJB Junction-to-board thermal resistance 24.8 16.9 26.1 °C/W
ψJT Junction-to-top characterization parameter 13.1 5.8 0.6 °C/W
ψJB Junction-to-board characterization parameter 23.8 16.8 26.3 °C/W
RθJC(bot) Junction-to-case (bottom) thermal resistance 2.4 2.3 7.4 °C/W
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
(2) Thermal resistance value RθJA is based on the EIA/JEDEC High-K printed circuit board defined by: JESD51-7, High Effective Thermal
Conductivity Test Board for Leaded Surface Mount Packages.
(3) The PCB for the NGN (WSON) package RθJA includes thermal vias under the exposed thermal pad per EIA/JEDEC JESD51-5.
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6.5 Electrical Characteristics
Unless otherwise specified VIN = 3.3 V, IOUT = 10 mA, CIN = 10 μF, COUT = 10 μF, VEN = VIN, VOUT = 1.8 V. Minimum and
maximum limits apply over the junction temperature (TJ) range of –40°C to +125°C and are specified through test, design, or
statistical correlation. Typical values represent the most likely parametric norm at TJ= 25°C, and are provided for reference
purposes only. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
2.7 V ≤VIN ≤5.5 V
10 mA ≤IOUT ≤1.5 A 0.584 0.605 0.626
TJ= 25°C
VADJ Adjust pin voltage(1) V
2.7 V ≤VIN ≤5.5 V 0.575 0.635
10 mA ≤IOUT ≤1.5 A
2.7 V ≤VIN ≤5.5 V
10 mA ≤IOUT ≤1.5 A 0.596 0.605 0.614
TJ= 25°C
VADJ Adjust pin voltage (A grade)(1) V
2.7 V ≤VIN ≤5.5 V 0.587 0.623
10 mA ≤IOUT ≤1.5 A
2.7 V ≤VIN ≤5.5 V 50 nA
TJ= 25°C
IADJ ADJUST pin bias current 2.7 V ≤VIN ≤5.5 V 750 nA
IOUT = 1.5 A 220 275 mV
TJ= 25°C
VDO Dropout voltage(2)
IOUT = 1.5 A 375 mV
2.7 V ≤VIN ≤5.5 V 0.04 %/V
ΔVOUT /TJ= 25°C
Output voltage line regulation(1)(3)
ΔVIN 2.7 V ≤VIN ≤5.5 V 0.05 %/V
10 mA < IOUT < 1.5 A 0.18 %/A
ΔVOUT / Output voltage load regulation(1) TJ= 25°C
ΔIOUT (4) 10 mA < IOUT < 1.5 A 0.33 %/A
10 mA < IOUT < 1.5 A 2 3.5
Ground pin current in normal TJ= 25°C
IGND mA
operation mode 10 mA < IOUT < 1.5 A 4.5
VEN < VIL(EN), TJ= 25°C 0.025 0.125
IDISABLED Ground pin current µA
VEN < VIL(EN) 15
IOUT(PK)GN Peak output current VOUT ≥VOUT(NOM) – 5% 3.6 A
D
ISC VOUT = 0 V, TJ= 25°C 3.7 A
Short-circuit current VOUT = 0 V 2
ENABLE INPUT (LP38502 Only)
VIH(EN) Enable logic high VOUT = ON 1.4 V
VIL(EN) Enable logic low VOUT = OFF 0.65 V
Time from VEN < VIL(EN) to VOUT =
td(off) Turnoff delay OFF 25 µs
ILOAD = 1.5 A
Time from VEN >VIH(EN) to VOUT = ON
td(on) Turnon delay 25 µs
ILOAD = 1.5A
IIH(EN) Enable pin high current VEN = VIN 1 nA
IIL(EN) Enable pin low current VEN = 0 V 0.1
(1) The line and load regulation specification contains only the typical number. However, the limits for line and load regulation are included
in the adjust voltage tolerance specification.
(2) Dropout voltage is defined as the minimum input to output differential voltage at which the output drops 2% below the nominal value. For
any output voltage less than 2.5V, the minimum VIN operating voltage is the limiting factor.
(3) Output voltage line regulation is defined as the change in output voltage from the nominal value due to change in the input line voltage.
(4) Output voltage load regulation is defined as the change in output voltage from the nominal value due to change in the load current.
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Electrical Characteristics (continued)
Unless otherwise specified VIN = 3.3 V, IOUT = 10 mA, CIN = 10 μF, COUT = 10 μF, VEN = VIN, VOUT = 1.8 V. Minimum and
maximum limits apply over the junction temperature (TJ) range of –40°C to +125°C and are specified through test, design, or
statistical correlation. Typical values represent the most likely parametric norm at TJ= 25°C, and are provided for reference
purposes only. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
AC PARAMETERS
VIN = 3 V, IOUT = 1.5 A, ƒ = 120 Hz 58
PSRR Ripple rejection dB
VIN = 3 V, IOUT = 1.5 A, ƒ = 1 kHz 56
ρn(l/f) Output noise density ƒ = 120 Hz, COUT = 10 µF CER 1 µV/√Hz
BW = 100 Hz – 100 kHz
enOutput noise voltage 100 µV(rms)
COUT = 10 µF CER
THERMALS
TSD Thermal shutdown TJrising 170 — °C
ΔTSD Thermal shutdown hysteresis TJfalling from TSD 10 — °C
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6.6 Typical Characteristics
Unless otherwise specified: TJ= 25°C, VIN = 2.7 V, VEN = VIN, CIN = 10 µF, COUT = 10 µF, IOUT = 10 mA, VOUT = 1.8 V.
Figure 2. Noise Density
Figure 1. Noise Density
Figure 4. IGND(OFF) vs Temperature
Figure 3. IGND vs Load Current
Figure 5. VADJ vs Temperature Figure 6. Dropout Voltage vs Load Current
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Typical Characteristics (continued)
Unless otherwise specified: TJ= 25°C, VIN = 2.7 V, VEN = VIN, CIN = 10 µF, COUT = 10 µF, IOUT = 10 mA, VOUT = 1.8 V.
Figure 7. VEN vs Temperature Figure 8. Turnon Characteristics
Figure 9. PSRR
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7 Detailed Description
7.1 Overview
The LP38500-ADJ and LP38502-ADJ are flex-cap and low-dropout adjustable regulators, the output voltage can
be set from 0.6 V to 5 V. Standard regulator features, such as overcurrent and overtemperature protections, are
also included.
The LP38500-ADJ and LP38502-ADJ contains several features:
●Stable with any type of output capacitor
●Fast load transient response
●Disable Mode (LP38502-ADJ only)
7.2 Functional Block Diagrams
Figure 10. LP38500-ADJ DDPAK/TO-263 Block Diagram
Figure 11. LP38502-ADJ DDPAK/TO-263 Block Diagram
Figure 12. LP38500-ADJ WSON Block Diagram
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Functional Block Diagrams (continued)
Figure 13. LP38502-ADJ WSON Block Diagram
7.3 Feature Description
7.3.1 Stability And Phase Margin
Any regulator which operates using a feedback loop must be compensated in such a way as to ensure adequate
phase margin, which is defined as the difference between the phase shift and –180 degrees at the frequency
where the loop gain crosses unity (0 dB). For most LDO regulators, the ESR of the output capacitor is required to
create a zero to add enough phase lead to ensure stable operation. The LP38500-ADJ and LP38502-ADJ each
have a unique internal compensation circuit which maintains phase margin regardless of the ESR of the output
capacitor, so any type of capacitor may be used.
Figure 14 shows the gain/phase plot of the LP38500-ADJ and LP38502-ADJ with an output of 1.2 V, a 10-µF
ceramic output capacitor, delivering 1.5 A of load current. It can be seen that the unity-gain crossover occurs at
150 kHz, and the phase margin is about 40° (which is very stable).
Figure 14. Gain-Bandwidth Plot for 1.5-A Load
Figure 15 shows the gain and phase with no external load. In this case, the only load is provided by the gain
setting resistors (about 12 kΩtotal in this test). It is immediately obvious that the unity-gain frequency is
significantly lower (dropping to about 500 Hz), at which point the phase margin is 125°.
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Feature Description (continued)
Figure 15. Gain-Bandwidth Plot for No Load
The reduction in unity-gain bandwidth as load current is reduced is normal for any LDO regulator using a P-FET
or PNP pass transistor, because they have a pole in the loop gain function given by:
(1)
This illustrates how the pole goes to the highest frequency when RLis minimum value (maximum load current).
In general, LDOs have maximum bandwidth (and lowest phase margin) at full load current. In the case of the
LP38500-ADJ or LP38502-ADJ, it can be seen that it has good phase margin even when using ceramic
capacitors with ESR values of only a few mΩ.
7.3.2 Load Transient Response
Load transient response is defined as the change in regulated output voltage which occurs as a result of a
change in load current. Many applications have loads which vary, and the control loop of the voltage regulator
must adjust the current in the pass FET transistor in response to load current changes. For this reason,
regulators with wider bandwidths often have better transient response.
The LP38500-ADJ and LP38502-ADJ employs an internal feed-forward design which makes the load transient
response much faster than would be predicted simply by loop speed: this feedforward means any voltage
changes appearing on the output are coupled through to the high-speed driver used to control the gate of the
pass FET along a signal path using very fast FET devices. Because of this, the pass transistor’s current can
change very quickly.
Figure 15 shows the output voltage load transient which occurs on a 1.8-V output when the load changes from
0.1 A to 1.5 A at an average slew rate of 0.5 A/µs. As shown, the peak output voltage change from nominal is
about 40 mV, which is about 2.2%.
Figure 16. Load Transient Response
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Feature Description (continued)
In cases where extremely fast load changes occur, the output capacitance may have to be increased. For fast
changing loads, the internal parasitics of ESR (equivalent series resistance) and ESL (equivalent series
inductance) degrade the capacitor’s ability to source current quickly to the load. The best capacitor types for
transient performance are (in order):
1. Multilayer Ceramic: with the lowest values of ESR and ESL, they can have ESR values in the range of a few
mΩ. Disadvantage: capacitance values above about 22 µF significantly increase in cost.
2. Low-ESR Aluminum Electrolytics: these are aluminum types (like OSCON) with a special electrolyte which
provides extremely low ESR values, and are the closest to ceramic performance while still providing large
amounts of capacitance. These are cheaper (by capacitance) than ceramic.
3. Solid tantalum: can provide several hundred µF of capacitance, transient performance is slightly worse than
OSCON type capacitors, cheaper than ceramic in large values.
4. General purpose aluminum electrolytics: cheap and provide a lot of capacitance, but give the worst
performance.
In general, managing load transients is done by paralleling ceramic capacitance with a larger bulk capacitance.
In this way, the ceramic can source current during the rapidly changing edge and the bulk capacitor can support
the load current after the first initial spike in current.
7.3.3 Dropout Voltage
The dropout voltage of a regulator is defined as the input-to-output differential required by the regulator to keep
the output voltage within 2% of the nominal value. For CMOS LDOs, the dropout voltage is the product of the
load current and the RDS(on) of the internal MOSFET pass element.
Since the output voltage is beginning to “drop out” of regulation when it drops by 2%, electrical performance of
the device will be reduced compared to the values listed in the Electrical Characteristics table for some
parameters (line and load regulation and PSRR would be affected).
7.3.4 Reverse Current Path
The internal MOSFET pass element in the LP38500-ADJ and LP38502-ADJ has an inherent parasitic diode.
During normal operation, the input voltage is higher than the output voltage and the parasitic diode is reverse
biased. However, if the output is pulled above the input in an application, then current flows from the output to
the input as the parasitic diode gets forward biased. The output can be pulled above the input as long as the
current in the parasitic diode is limited to 200-mA continuous and 1-A peak. The regulator output pin should not
be taken below ground potential. If the LP38500-ADJ and LP38502-ADJ is used in a dual-supply system where
the regulator load is returned to a negative supply, the output must be diode-clamped to ground.
7.4 Device Functional Modes
7.4.1 Short-Circuit Protection
The LP38500-ADJ and LP38502-ADJ contain internal current limiting which will reduce output current to a safe
value if the output is overloaded or shorted. Depending upon the value of VIN, thermal limiting may also become
active as the average power dissipated causes the die temperature to increase to the limit value (about 170°C).
The hysteresis of the thermal shutdown circuitry can result in a “cyclic” behavior on the output as the die
temperature heats and cools.
7.4.2 Enable Operation (LP38502-ADJ Only)
The Enable pin (EN) must be actively terminated by either a 10-kΩpull-up resistor to VIN, or a driver which
actively pulls high and low (such as a CMOS rail to rail comparator). If active drive is used, the pull-up resistor is
not required. This pin must be tied to VIN if not used (it must not be left floating).
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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
The LP38500-ADJ and LP38502-ADJ devices can provide 1.5-A output current with 2.7-V to 5.5-V input voltage.
These ultra-low-dropout linear regulators respond very quickly to step changes in load, making them suitable for
low-voltage microprocessor applications. Input and output capacitors of at least 10 µF are required.
8.2 Typical Applications
Figure 17. Typical Circuit (LP38500) Figure 18. Typical Circuit (LP38502)
8.2.1 Design Requirements
For LP3850x-ADJ typical applications, use the parameters listed in Table 1 as the input parameters.
Table 1. Design Parameters
DESIGN PARAMETERS VALUE
Input voltage 2.7 V to 5.5 V
Output voltage 0.6 V to 5 V (adjustable)
Output current 1.5 A (maximum)
Input capacitor 10 µF (minimum)
Output capacitor 10 uF (minimum)
8.2.2 Detailed Design Procedure
8.2.2.1 External Capacitors
The LP38500-ADJ and LP38502-ADJ require that at least 10-µF (±20%) capacitors be used at the input and
output pins located within one cm of the device. Larger capacitors may be used without limit on size for both CIN
and COUT. Capacitor tolerances such as temperature variation and voltage loading effects must be considered
when selecting capacitors to ensure that they will provide the minimum required amount of capacitance under all
operating conditions for the application.
In general, ceramic capacitors are best for noise bypassing and transient response because of their ultra low
ESR. It must be noted that if ceramics are used, only the types with X5R or X7R dielectric ratings should be used
(never Z5U or Y5F). Capacitors which have the Z5U or Y5F characteristics will see a drop in capacitance of as
much as 50% if their temperature increases from 25°C to 85°C. In addition, the capacitance drops significantly
with applied voltage: a typical Z5U or Y5F capacitor can lose as much as 60% of its rated capacitance if only half
of the rated voltage is applied to it. For these reasons, only X5R and X7R ceramics should be used.
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8.2.2.2 Input Capacitor
All linear regulators can be affected by the source impedance of the voltage which is connected to the input. If
the source impedance is too high, the reactive component of the source may affect the control loop’s phase
margin. To ensure proper loop operation, the ESR of the capacitor used for CIN must not exceed 0.5 Ω. Any
good quality ceramic capacitor will meet this requirement, as well as many good quality tantalums. Aluminum
electrolytic capacitors may also work, but can possibly have an ESR which increases significantly at cold
temperatures. If the ESR of the input capacitor may exceed 0.5 Ω, it is recommended that a 2.2-µF ceramic
capacitor be used in parallel, as this will assure stable loop operation.
8.2.2.3 Output Capacitor
Any type of capacitor may be used for COUT, with no limitations on minimum or maximum ESR, as long as the
minimum amount of capacitance is present. The amount of capacitance can be increased without limit.
Increasing the size of COUT typically will give improved load transient response.
8.2.2.4 Setting The Output Voltage
The output voltage of the LP38500/2-ADJ can be set to any value between 0.6V and 5V using two external
resistors shown as R1 and R2 in Figure 19.
Figure 19. Setting Output Voltage
The value of R2 should always be less than or equal to 10 kΩfor good loop compensation. R1 can be selected
for a given VOUT using the following formula:
VOUT = VADJ (1 + R1/R2) + IADJ (R1)
where
• VADJ is the adjust pin voltage
• IADJ is the bias current flowing into the adjust pin (2)
8.2.2.5 RFI/EMI Susceptibility
Radio Frequency Interference (RFI) and Electro-Magnetic Interference (EMI) can degrade any integrated circuit's
performance because of the small dimensions of the geometries inside the device. In applications where circuit
sources are present which generate signals with significant high frequency energy content (> 1 MHz), care must
be taken to ensure that this does not affect the device regulator.
If RFI/EMI noise is present on the input side of the regulator (such as applications where the input source comes
from the output of a switching regulator), good ceramic bypass capacitors must be used at the input pin of the
device to reduce the amount of EMI conducted into the device.
If the LP38500, LP38502-ADJ output is connected to a load which switches at high speed (such as a clock), the
high-frequency current pulses required by the load must be supplied by the capacitors on the device output.
Since the bandwidth of the regulator loop is less than 300 kHz, the control circuitry cannot respond to load
changes above that frequency. This means the effective output impedance of the device at frequencies above
300 kHz is determined only by the output capacitor(s). Ceramic capacitors provide the best performance in this
type of application.
14 Submit Documentation Feedback Copyright © 2007–2015, Texas Instruments Incorporated
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LP38500-ADJ
,
LP38502-ADJ
www.ti.com
SNVS539H –NOVEMBER 2007–REVISED SEPTEMBER 2015
In applications where the load is switching at high speed, the output of the device may need RF isolation from
the load. In such cases, it is recommended that some inductance be placed between the output capacitor and
the load, and good RF bypass capacitors be placed directly across the load. PCB layout is also critical in high
noise environments, since RFI/EMI is easily radiated directly into PC traces. Noisy circuitry should be isolated
from clean circuits where possible, and grounded through a separate path. At MHz frequencies, ground planes
begin to look inductive and RFI/EMI can cause ground bounce across the ground plane. In multi-layer PC Board
applications, care should be taken in layout so that noisy power and ground planes do not radiate directly into
adjacent layers which carry analog power and ground.
8.2.2.6 Output Noise
Noise is specified in two ways:
• Spot noise or output noise density is the RMS sum of all noise sources, measured at the regulator output, at
a specific frequency (measured with a 1-Hz bandwidth). This type of noise is usually plotted on a curve as a
function of frequency.
• Total output noise or broadband noise is the RMS sum of spot noise over a specified bandwidth, usually
several decades of frequencies.
Spot noise is measured in units µV/√Hz or nV/√Hz and total output noise is measured in µV(rms). The primary
source of noise in low-dropout regulators is the internal reference. In CMOS regulators, noise has a low-
frequency component and a high frequency component, which depend strongly on the silicon area and quiescent
current.
Noise can generally be reduced in two ways: increase the transistor area or increase the reference current.
However, enlarging the transistors will increase die size, and increasing the reference current means higher total
supply current (ground pin current).
8.2.3 Application Curves
Figure 21. Turnon Time
Figure 20. Turnon Time
Copyright © 2007–2015, Texas Instruments Incorporated Submit Documentation Feedback 15
Product Folder Links: LP38500-ADJ LP38502-ADJ
LP38500-ADJ
,
LP38502-ADJ
SNVS539H –NOVEMBER 2007–REVISED SEPTEMBER 2015
www.ti.com
9 Power Supply Recommendations
The LP38500-ADJ and LP38502-ADJ devices are designed to operate from an input voltage supply range
between 2.7 V and 5.5 V. The input voltage range provides adequate headroom in order for the device to have a
regulated output. This input supply must be well regulated. An input capacitor of at least 10 μF is required.
9.1 Power Dissipation/Heatsinking
The maximum power dissipation (PD(MAX)) of the LP38500-ADJ and LP38502-ADJ is limited by the maximum
junction temperature of 125°C, along with the maximum ambient temperature (TA(MAX)) of the application, and the
thermal resistance (RθJA) of the package. Under all possible conditions, the junction temperature (TJ) must be
within the range specified in the Recommended Operating Conditions. The total power dissipation of the device
is given by:
PD= ((VIN −VOUT) × IOUT) + (VIN × IGND)
where
• IGND is the operating ground current of the device (specified under Electrical Characteristics) (3)
The maximum allowable junction temperature rise (ΔTJ) depends on the maximum expected ambient
temperature (TA(MAX)) of the application, and the maximum allowable junction temperature (TJ(MAX)):
ΔTJ= TJ(MAX)−TA(MAX) (4)
The maximum allowable value for junction-to-ambient thermal resistance, RθJA, can be calculated using the
formula:
RθJA =ΔTJ/ PD(MAX) (5)
The LP38500-ADJ and LP38502-ADJ are available in the DDPAK/TO-263, TO-263, and WSON packages. The
thermal resistance depends on the amount of copper area allocated to heat transfer.
16 Submit Documentation Feedback Copyright © 2007–2015, Texas Instruments Incorporated
Product Folder Links: LP38500-ADJ LP38502-ADJ
Ground
IN OUT
N/C
Input
Capacitor Output
Capacitor
ADJ
R2
R1
LP38500-ADJ
,
LP38502-ADJ
www.ti.com
SNVS539H –NOVEMBER 2007–REVISED SEPTEMBER 2015
10 Layout
10.1 Layout Guidelines
10.1.1 Printed Circuit Board Layout
Good layout practices will minimize voltage error and prevent instability which can result from ground loops. The
input and output capacitors should be directly connected to the device pins with short traces that have no other
current flowing in them (Kelvin connect).
The best way to do this is to place the capacitors very near the device and make connections directly to the
device pins via short traces on the top layer of the PCB. The regulator’s ground pin should be connected through
vias to the internal or backside ground plane so that the regulator has a single point ground.
The external resistors which set the output voltage must also be located very near the device with all connections
directly tied via short traces to the pins of the device (Kelvin connect). Do not connect the resistive divider to the
load point or DC error will be induced.
10.2 Layout Examples
Figure 22. LP38500-ADJ TO-263 Layout (LP38500)
Copyright © 2007–2015, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Links: LP38500-ADJ LP38502-ADJ
Ground
VOUT
VIN
Input
Capacitor
Output
Capacitor
BYPASS
N/C
GROUND
IN OUT
SHUTDOWN
SENSE
ERROR
Error Pullup
Resistor VOUT
Ground
IN OUT
EN
Input
Capacitor Output
Capacitor
Pull-up
Resistor
ADJ
R2
R1
LP38500-ADJ
,
LP38502-ADJ
SNVS539H –NOVEMBER 2007–REVISED SEPTEMBER 2015
www.ti.com
Layout Examples (continued)
Figure 23. LP38502-ADJ TO-263 Layout
Figure 24. LP3850x WSON Layout
10.2.1 Heatsinking WSON Package
The junction-to-ambient thermal resistance for the WSON package is dependent on how much PCB copper is
present to conduct heat away from the device. The LP38502SD-ADJ evaluation board (980600046-100) was
tested and gave a result of about 52.5°C/W with a power dissipation of 1 W and no external airflow. This
evaluation board is a two layer board using two ounce copper, and the copper area on topside for heatsinking is
approximately two square inches. Multiple vias under the DAP also thermally connect to the backside layer which
has about three square inches of copper dedicated to heatsinking.
With four thermal vias directly under the DAP to the first copper plane, the modeling predicts a RθJA of 52.5°C/W.
Adding a dog-bone copper area with four additional thermal vias in the dog-bone area to the first copper plane
can improve RθJA to 45°C/W.
18 Submit Documentation Feedback Copyright © 2007–2015, Texas Instruments Incorporated
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LP38500-ADJ
,
LP38502-ADJ
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SNVS539H –NOVEMBER 2007–REVISED SEPTEMBER 2015
Layout Examples (continued)
See Application Note AN-1520 A Guide to Board Layout for Best Thermal Resistance for Exposed Packages
(SNVA183) for additional thermal considerations for printed circuit board layouts.
Copyright © 2007–2015, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Links: LP38500-ADJ LP38502-ADJ
LP38500-ADJ
,
LP38502-ADJ
SNVS539H –NOVEMBER 2007–REVISED SEPTEMBER 2015
www.ti.com
11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
Application Note AN-1520 A Guide to Board Layout for Best Thermal Resistance for Exposed Packages
(SNVA183).
11.1.2 Related Links
Table 2 lists quick access links. Categories include technical documents, support and community resources,
tools and software, and quick access to sample or buy.
Table 2. Related Links
TECHNICAL TOOLS & SUPPORT &
PARTS PRODUCT FOLDER SAMPLE & BUY DOCUMENTS SOFTWARE COMMUNITY
LP38500-ADJ Click here Click here Click here Click here Click here
LP38502-ADJ Click here Click here Click here Click here Click here
11.2 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.
11.3 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.4 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.
11.5 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.
20 Submit Documentation Feedback Copyright © 2007–2015, Texas Instruments Incorporated
Product Folder Links: LP38500-ADJ LP38502-ADJ
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LP38500ASD-ADJ/NOPB WSON NGS 8 1000 178.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38500ASDX-ADJ/NOP
BWSON NGS 8 4500 330.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38500ATJ-ADJ/NOPB TO-263 NDQ 5 1000 330.0 24.4 10.6 15.4 2.45 12.0 24.0 Q2
LP38500SD-ADJ/NOPB WSON NGS 8 1000 178.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38500SDE-ADJ/NOPB WSON NGS 8 250 178.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38500SDX-ADJ/NOPB WSON NGS 8 4500 330.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38500TJ-ADJ/NOPB TO-263 NDQ 5 1000 330.0 24.4 10.6 15.4 2.45 12.0 24.0 Q2
LP38500TSX-ADJ/NOPB DDPAK/
TO-263 KTT 5 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2
LP38502ASD-ADJ/NOPB WSON NGS 8 1000 180.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38502ASDX-ADJ/NOP
BWSON NGS 8 4500 330.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38502ATJ-ADJ/NOPB TO-263 NDQ 5 1000 330.0 24.4 10.6 15.4 2.45 12.0 24.0 Q2
LP38502SD-ADJ/NOPB WSON NGS 8 1000 180.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38502SDE-ADJ/NOPB WSON NGS 8 250 178.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38502SDX-ADJ/NOPB WSON NGS 8 4500 330.0 12.4 3.3 2.8 1.0 8.0 12.0 Q1
LP38502TJ-ADJ/NOPB TO-263 NDQ 5 1000 330.0 24.4 10.6 15.4 2.45 12.0 24.0 Q2
LP38502TSX-ADJ/NOPB DDPAK/ KTT 5 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2
PACKAGE MATERIALS INFORMATION
www.ti.com 5-Jan-2021
Pack Materials-Page 1
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
TO-263
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LP38500ASD-ADJ/NOPB WSON NGS 8 1000 210.0 185.0 35.0
LP38500ASDX-ADJ/NOPB WSON NGS 8 4500 367.0 367.0 35.0
LP38500ATJ-ADJ/NOPB TO-263 NDQ 5 1000 367.0 367.0 35.0
LP38500SD-ADJ/NOPB WSON NGS 8 1000 210.0 185.0 35.0
LP38500SDE-ADJ/NOPB WSON NGS 8 250 210.0 185.0 35.0
LP38500SDX-ADJ/NOPB WSON NGS 8 4500 367.0 367.0 35.0
LP38500TJ-ADJ/NOPB TO-263 NDQ 5 1000 367.0 367.0 35.0
LP38500TSX-ADJ/NOPB DDPAK/TO-263 KTT 5 500 367.0 367.0 45.0
LP38502ASD-ADJ/NOPB WSON NGS 8 1000 200.0 183.0 25.0
LP38502ASDX-ADJ/NOPB WSON NGS 8 4500 367.0 367.0 35.0
LP38502ATJ-ADJ/NOPB TO-263 NDQ 5 1000 367.0 367.0 35.0
LP38502SD-ADJ/NOPB WSON NGS 8 1000 200.0 183.0 25.0
LP38502SDE-ADJ/NOPB WSON NGS 8 250 210.0 185.0 35.0
LP38502SDX-ADJ/NOPB WSON NGS 8 4500 367.0 367.0 35.0
LP38502TJ-ADJ/NOPB TO-263 NDQ 5 1000 367.0 367.0 35.0
LP38502TSX-ADJ/NOPB DDPAK/TO-263 KTT 5 500 367.0 367.0 45.0
PACKAGE MATERIALS INFORMATION
www.ti.com 5-Jan-2021
Pack Materials-Page 2
MECHANICAL DATA
KTT0005B
www.ti.com
BOTTOM SIDE OF PACKAGE
TS5B (Rev D)
MECHANICAL DATA
NDQ0005A
www.ti.com
TJ5A (Rev F)
www.ti.com
PACKAGE OUTLINE
C
8X 0.3
0.2
1.5 0.1
8X 0.5
0.3
2X
1.5
1.6 0.1
6X 0.5
0.8
0.7
0.05
0.00
B3.1
2.9 A
2.6
2.4
(0.1) TYP
WSON - 0.8 mm max heightNGS0008C
PLASTIC SMALL OUTLINE - NO LEAD
4214924/A 07/2018
PIN 1 INDEX AREA
SEATING PLANE
0.08 C
1
45
8
PIN 1 ID 0.1 C A B
0.05 C
THERMAL PAD
EXPOSED
9
SYMM
SYMM
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.
SCALE 5.000
www.ti.com
EXAMPLE BOARD LAYOUT
0.07 MIN
ALL AROUND
0.07 MAX
ALL AROUND
(1.6)
6X (0.5)
(2.8)
8X (0.25)
8X (0.6)
(1.5)
(R0.05) TYP ( 0.2) VIA
TYP
(0.5)
WSON - 0.8 mm max heightNGS0008C
PLASTIC SMALL OUTLINE - NO LEAD
4214924/A 07/2018
SYMM
1
45
8
SYMM
LAND PATTERN EXAMPLE
EXPOSED METAL SHOWN
SCALE:20X
9
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.
SOLDER MASK
OPENING
SOLDER MASK
METAL UNDER
SOLDER MASK
DEFINED
EXPOSED METAL
METAL
SOLDER MASK
OPENING
SOLDER MASK DETAILS
NON SOLDER MASK
DEFINED
(PREFERRED)
EXPOSED METAL
www.ti.com
EXAMPLE STENCIL DESIGN
8X (0.25)
8X (0.6)
6X (0.5)
(1.38)
(1.47)
(2.8)
(R0.05) TYP
WSON - 0.8 mm max heightNGS0008C
PLASTIC SMALL OUTLINE - NO LEAD
4214924/A 07/2018
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 0.1 mm THICK STENCIL
EXPOSED PAD 9:
82% PRINTED SOLDER COVERAGE BY AREA UNDER PACKAGE
SCALE:20X
SYMM
1
45
8
SYMM
METAL
TYP
9
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