FAN53528EUC48X - ON SEMICONDUCTOR

February, 2019 − Rev. 2

1Publication Order Number:

FAN53528/D

FAN53528

3.0 A, 2.4 MHz, Digitally

Programmable Buck

Regulator

Descriptions

The FAN53528 is a step−down switching voltage regulator that

delivers a digitally programmable output from an input voltage supply

of 2.5 V to 5.5 V. The output voltage is programmed through an I2C

interface capable of operating up to 3.4 MHz.

Using a proprietary architecture with synchronous rectification, the

FAN53528 is capable of delivering 3.0 A continuous at over 80%

efficiency, maintaining that efficiency at load currents as low as

10 mA. The regulator operates at a nominal fixed frequency of

2.4 MHz, which reduces the value of the external components.

Additional output capacitance can be added to improve regulation

during load transients without affecting stability.

At moderate and light−loads, Pulse Frequency Modulation (PFM) is

used to operate in Power−Save Mode with a typical quiescent current

of 50 mA at room temperature. Even with such a low quiescent

current, the part exhibits excellent transient response during large load

swings. At higher loads, the system automatically switches to

fixed−frequency control, operating at 2.4 MHz. In Shutdown Mode,

the supply current drops below 1 mA, reducing power consumption.

PFM Mode can be disabled if fixed frequency is desired. The

FAN53528 is available in a 15−bump, 1.310 mm × 2.015 mm, 0.4 mm

ball pitch WLCSP.

Features

•Fixed−Frequency Operation: 2.4 MHz

•Best−in−Class Load Transient

•Continuous Output Current Capability: 3.0 A

•2.5 V to 5.5 V Input Voltage Range

•Digitally Programmable Output Voltage:

♦0.35 V to 1.14375 V in 6.25 mV Steps

•Programmable Slew Rate for Voltage Transitions

•I2C−Compatible Interface Up to 3.4 Mbps

•PFM Mode for High Efficiency in Light-Load

•Quiescent Current in PFM Mode: 50 mA (Typical)

•Input Under−Voltage Lockout (UVLO)

•Thermal Shutdown and Overload Protection

•15−Bump Wafer−Level Chip Scale Package (WLCSP)

Applications

•Application, Graphic, and DSP Processors

♦ARMt, Tegrat, OMAPt, NovaThort,

ARMADAt, Kraitt, etc.

•Hard Disk Drives, LPDDR3, LPDDR4

•Tablets, Netbooks, Ultra−Mobile PCs

•Smart Phones

•Gaming Devices

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See detailed ordering and shipping information on page 2 of

this data sheet.

ORDERING INFORMATION

WLCSP−15

CASE 567QS

MARKING DIAGRAM

1, 2 = Two Alphanumeric Characters

for Device Mark

KK = Two Alphanumeric Characters

for Lot Rune Code Mark

. = Pin 1 Indicator

X = Alphabetical Year Code

Y= 2−weeks Date Code

Z = Assembly Plant Code

Pin−1

Mark

2KK

XYZ

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FAN SW

PGND

CIN

VOUT

AGND

LOADVSEL

SCL

SDA

CBY

Figure 1. Typical Application

53528

VIN

OUT1,2

PACKAGE MARKING AND ORDERING INFORMATION

Part Number

Power−Up

Defaults

EN Delay

Temperature

Range Package

Packing

Method

Device

Marking

VSEL0 VSEL1

FAN53528BUC08X 0.4 0.6 No −40 to 85_CWLCSP Tape & Reel FX

FAN53528DUC40X 0.6 0.9 No FY

FAN53528GUC48X 0.65 0.7 No FZ

FAN53528EUC48X 0.65 0.7 5 ms FW

*FAN53528DUC1204X 1.1 0.9 No TBD

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.

*This device is not released yet.

RECOMMENDED EXTERNAL COMPONENTS

Table 1. RECOMMENDED EXTERNAL COMPONENTS FOR 3.0 A MAXIMUM LOAD CURRENT

Component Description Vendor Parameter Typ. Unit

L1 330 nH, 2016 Case Size See Table 2

L1 Alternative (Note 1) 470 nH 2016 Case Size

COUT1, COUT2 22 mF, 6.3 V, X5R, 0603 C1608X5R0J226M080AC (TDK) C 22 mF

CIN 1 Piece; 4.7 mF, 10 V, X5R, 0603 C1608X5R1A475K (TDK) C 4.7

CBY (Note 1) 1 Piece; 100 nF, 6.3V, X5R, 0201 GRM033R60J104KE19D (Murata) C 100 nF

1. L1 Alternative can be used if not following reference design. CBY is recommended to reduce any high frequency component on VIN bus.

CBY is optional and used to filter any high frequency component on VIN bus.

Table 2. RECOMMENDED INDUCTORS

Manufacturer Part # L (nH)

DCR

(mW Typ.)

ISAT

(Note 2)

Component Dimensions

L W H

Toko DFE201610E−R33N 330 21 6.1 2.0 1.6 1.0

Toko DFE201610E−R47N 470 26 5.3 2.0 1.6 1.0

2. ISAT where the dc current drops the inductance by 30%.

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PIN CONFIGURATION

PGND AGND

VSEL SDAEN

SCL VOUTAGND

PGNDSWVIN

A1 A2

D1 D3D2

E1 E3E2

Figure 2. Pin Configuration

A3 A2

D1D3 D2

E1E3 E2

Top View Bottom View

Table 3. PIN DEFINITIONS

Pin # Name Description

D1 VSEL Voltage Select. When this pin is LOW, VOUT is set by the VSEL0 register. When this pin is HIGH,

VOUT is set by the VSEL1 register. Polarity of pin in conjunction with the MODE bits in the Control

and VSEL1 = FPWM. The VSEL pin has an internal pull−down resistor (250 kW), which is only

activated with a logic low.

D2 EN Enable. The device is in Shutdown Mode when this pin is LOW. Device keeps register content

when EN pin is LOW. The EN Pin has an internal pull−down resistor (250 kW), which is only acti-

vated with a logic low.

E2 SCL I2C Serial Clock

D3 SDA I2C Serial Data

E3 VOUT VOUT. Sense pin for VOUT

. Connect to COUT

A3, B3, C2 PGND Power Ground. The low−side MOSFET is referenced to this pin. CIN and COUT should be returned

with a minimal path to these pins.

C3, E1 AGND Analog Ground. All signals are referenced to this pin. Avoid routing high di/dt AC currents through

this pin.

A1, B1, C1 VIN Power Input Voltage. Connect to the input power source. Connect to CIN with minimal path.

A2, B2 SW Switching Node. Connect to the inductor.

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Table 4. ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Parameter Min Max Unit

VIN Voltage on SW, VIN Pins IC Not Switching −0.3 7.0 V

IC Switching −0.3 6.5

Voltage on EN Pin −0.3 VIN

(Note 3)

Voltage on All Other Pins IC Not Switching −0.3 VIN

(Note 3)

VOUT Voltage on VOUT Pin −0.3 6.5 V

VINOV_SLEW Maximum Slew Rate of VIN > 6.5V, PWM Switching 100 V/ms

ESD Human Body Model, ANSI/ESDA/JEDEC JS−001−2012 2000 V

Charged Device Model per JESD22−C101 1000

TJJunction Temperature −40 +150 °C

TSTG Storage Temperature −65 +150 °C

TLLead Soldering Temperature, 10 Seconds +260 °C

Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality

should not be assumed, damage may occur and reliability may be affected.

3. Lesser of 7V or VIN + 0.3 V.

Table 5. RECOMMENDED OPERATING CONDITIONS

Symbol Parameter Min. Typ. Max. Unit

VIN Supply Voltage Range 2.5 5.5 V

IOUT Output Current 0 3.0 A

TAOperating Ambient Temperature −40 +85 °C

TJOperating Junction Temperature −40 +125 °C

Functional operation above the stresses listed in the Recommended Operating Ranges is not implied. Extended exposure to stresses beyond

the Recommended Operating Ranges limits may affect device reliability.

Table 6. THERMAL PROPERTIES

Symbol Parameter Min. Typ. Max. Unit

θJA Junction−to−Ambient Thermal Resistance (Note 4) 42 °C/W

4. Junction−to−ambient thermal resistance is a function of application and board layout. This data is simulated with four−layer 2s2p boards with

vias in accordance to JESD51− JEDEC standard. Special attention must be paid not to exceed the junction temperature

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Table 7. ELECTRICAL CHARACTERISTICS

Minimum and maximum values are at VIN = 3.6 V, TA = −40°C to +85°C, unless otherwise noted.

Typical values are at TA = 25°C, VIN = 3.6 V, VOUT = 0.4 V and EN = 1.8 V.

Symbol Parameter Condition Min. Typ. Max. Unit

POWER SUPPLIES

IQQuiescent Current ILOAD = 0 50 mA

I SD H/W Shutdown Supply Current EN = GND 0.1 3.0 mA

S/W Shutdown Supply Current EN = 1.8 V, BUCK_ENx = 0,

2.5 V ≤ VIN ≤ 5.5 V

2 12 mA

VUVLO Under−Voltage Lockout Threshold VIN Rising 2.32 2.45 V

VUVHYST Under−Voltage Lockout Hysteresis 350 mV

EN, VSEL, SDA, SCL

VIH HIGH−Level Input Voltage 2.5 V ≤ VIN ≤ 5.5 V 1.1 V

VIL LOW−Level Input Voltage 2.5 V ≤ VIN ≤ 5.5 V 0.4 V

IIN Input Bias Current Input Tied to GND or VIN 0.01 1.00 mA

VOUT REGULATION

VREG VOUT DC Accuracy 2.8 V ≤ VIN ≤ 4.8 V, VOUT = 0.4 V,

IOUT(DC) = 0 A, Auto Mode

−3 +5 %

2.8 V ≤ VIN ≤ 4.8 V, VOUT = 0.4 V,

IOUT(DC) = 0 A, Forced PWM Mode

−1.5 +1.5

2.8 V ≤ VIN ≤ 4.8 V, VOUT from

Minimum to Maximum,

IOUT(DC) = 0 to 3.0 A, Auto Mode

−4 +6

POWER SWITCH/PROTECTION

ILIMPK P−MOS Peak Current Limit 4.00 4.75 5.50 A

TLIMIT Thermal Shutdown 150 °C

THYST Thermal Shutdown Hysteresis 17 °C

VSDWN Input OVP Shutdown Rising Threshold 6.15 V

Falling Threshold 5.50 5.73

FREQUENCY CONTROL

fSW Oscillator Frequency 2.05 2.40 2.75 MHz

DAC

Resolution 7 Bits

Differential Nonlinearity (Note 5) 0.5 LSB

Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product

performance may not be indicated by the Electrical Characteristics if operated under different conditions.

5. Monotonicity assured by design.

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Table 8. SYSTEM CHARACTERISTICS

The following system characteristics are guaranteed by design and are not performed in production testing. Recommended operating

conditions, unless otherwise noted, VIN =2.5 V to 5.5 V, TA = −40°C to +85°C, VOUT =0.4 V.

Typical values are given at TA = 25°C, VIN =3.6 V. System characteristics are based on circuit per Figure 1.

L = 0.33 mH, DFE201610E−R33M (TOKO), CIN = 1 × 4.7 mF, 10 V, 0603 (1608 metric), C1608X5R1A475K (TDK) and COUT = 2 × 22 mF

(6.3 V, 0603, TDK C1608X5R0J226M080AC) + 4 ×100 mF (6.3 V, 0201, Murata GRM033R60J104KE19D) + 1 × 4.7 mF (6.3 V, 0402, TDK

C1005X5R0J475M050BC).

Symbol Parameter Condition Min. Typ. Max. Unit

LOADREG Load Regulation IOUT = 0 A to 3 A, Forced PWM Mode 0.05 %/A

LINEREG Line Regulation 2.5 V ≤ VIN ≤ 5.5 V, IOUT =1.5 A 0.09 %/V

VOUT_RIPPLE Ripple Voltage IOUT = 20 mA, PFM Mode 16 mV

IOUT = 700 mA, PFM Mode 5

DVOUT_LOAD Load Transient IOUT = 10 mA ⇔ 700 mA,

tR = tF = 200 ns, VOUT = 0.4 V, Auto Mode

±20 mV

IOUT = 0 mA ⇔ 800 mA,

tR = tF = 0.9 ms, VIN = 3.2 V, VOUT = 1.125 V,

Auto Mode

±13

IOUT = 0 mA ⇔ 800 mA,

tR = tF = 0.9 ms, VIN = 3.8 V, VOUT = 1.125 V,

Auto Mode

±15

DVOUT_LINE Line Transient VIN = 3.0 V ⇔ 3.6 V,

tR = tF = 10 ms, IOUT = 100 mA, Forced PWM Mode

±11 mV

tss Soft−Start EN High to 95% of Target_VOUT (0.4 V),

IOUT = 200 mA; FAN53528BUC08X

85 ms

tdelay EN Delay EN High to VOUT Start−to−Rise,

VOUT = 0.65 V, IOUT = 0 A; FAN53528EUC48X

5 ms

Table 9. I2C TIMING SPECIFICATIONS

Guaranteed by design.

Symbol Parameter Condition Min. Typ. Max. Unit

fSCL SCL Clock Frequency Standard Mode 100 kHz

Fast Mode 400 kHz

Fast Mode Plus 1000

High−Speed Mode, CB ≤100 pF 3400

High−Speed Mode, CB ≤ 400 pF 1700

tBUF Bus−Free Time between STOP and

START Conditions

Standard Mode 4.7 ms

Fast Mode 1.3

Fast Mode Plus 0.5

tHD;STA START or REPEATED START

Hold Time

Standard Mode 4ms

Fast Mode 600 ns

Fast Mode Plus 260

High−Speed Mode 160

tLOW SCL LOW Period Standard Mode 4.7 ms

Fast Mode 1.3

Fast Mode Plus 0.5

High−Speed Mode, CB ≤ 100 pF 160 ns

High−Speed Mode, CB ≤ 400 pF 320

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Table 9. I2C TIMING SPECIFICATIONS (continued)

Guaranteed by design.

Symbol UnitMax.Typ.Min.ConditionParameter

tHIGH SCL HIGH Period Standard Mode 4ms

Fast Mode 600 ns

Fast Mode Plus 260

High−Speed Mode, CB ≤ 100 pF 60

High−Speed Mode, CB ≤ 400 pF 120

tSU;STA Repeated START Setup Time Standard Mode 4.7 ms

Fast Mode 600 ns

Fast Mode Plus 260

High−Speed Mode 160

tSU;DAT Data Setup Time Standard Mode 250 ns

Fast Mode 100

Fast Mode Plus 50

High−Speed Mode 10

tHD;DAT Data Hold Time Standard Mode 0 3.45 ms

Fast Mode 0 900 ns

Fast Mode Plus 0 450

High−Speed Mode, CB ≤ 100 pF 0 70

High−Speed Mode, CB ≤ 400 pF 0 150

tRCL SCL Rise Time Standard Mode 20+0.1CB1000 ns

Fast Mode 20+0.1CB300

Fast Mode Plus 20+0.1CB120

High−Speed Mode, CB ≤ 100 pF 10 80

High−Speed Mode, CB ≤ 400 pF 20 160

tFCL SCL Fall Time Standard Mode 20+0.1CB300 ns

Fast Mode 20+0.1CB300

Fast Mode Plus 20+0.1CB120

High−Speed Mode, CB ≤ 100 pF 10 40

High−Speed Mode, CB ≤ 400 pF 20 80

tRCL1 Rise Time of SCL After a

REPEATED START Condition and

After ACK Bit

High−Speed Mode, CB ≤ 100 pF 10 80 ns

High−Speed Mode, CB ≤ 400 pF 20 160

tRDA SDA Rise Time Standard Mode 20+0.1CB1000 ns

Fast Mode 20+0.1CB300

Fast Mode Plus 20+0.1CB120

High−Speed Mode, CB ≤ 100 pF 10 80

High−Speed Mode, CB ≤ 400 pF 20 160

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Table 9. I2C TIMING SPECIFICATIONS (continued)

Guaranteed by design.

Symbol UnitMax.Typ.Min.ConditionParameter

tFDA SDA Fall Time Standard Mode 20+0.1CB300 ns

Fast Mode 20+0.1CB300

Fast Mode Plus 20+0.1CB120

High−Speed Mode, CB ≤ 100 pF 10 80

High−Speed Mode, CB ≤ 400 pF 20 160

tSU;STO Stop Condition Setup Time Standard Mode 4ms

Fast Mode 600 ns

Fast Mode Plus 120

High−Speed Mode 160

CBCapacitive Load for SDA and SCL 400 pF

Timing Diagrams

ÎÎ

ÏÏ

START

ÌÌ

ÑÑ

ÓÓÓ

REPEATED

START

ÔÔ

SCL

SDA

tHD;STA

tLOW

tHD;DAT

tHIGH

TSU;DAT

tSU;STA

tHD;STO

tBUF

ÖÖ

START

ÒÒ

STOP

tHD;STA

Figure 3. I2C Interface Timing for Fast Plus, Fast, and Slow Modes

REPEATED

START

SCLH

SDAH

tFDA

tLOW

tRCL1

tHD;DAT

tHIGH

tSU;STO

REPEATED

START

tRDA

tFCL

tSU;DAT

tRCL

STOP

= MCS Current Source Pull−up

= RP Resistor Pull−up

note A

Note A: First rising edge of SCLH after Repeated Start and after each ACK bit.

tHD;STA

tSU;STA

Figure 4. I2C Interface Timing for High−Speed Mode

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TYPICAL CHARACTERISTICS

Unless otherwise specified, VIN = 3.6 V, VOUT = 0.4 V, Auto Mode, TA = 25°C; circuit and components according to Figure 1 and Table 1.

Figure 5. Efficiency vs. Load Current and Input

Voltage, VOUT = 0,4 V, Auto Mode

Figure 6. Efficiency vs. Load Current and

Temperature, VIN = 3.6 V, VOUT = 0.4 V, Auto Mode

Figure 7. Output Regulation vs. Load Current and

Input Voltage, VOUT = 0.4 V, Auto Mode

Figure 8. Frequency vs. Load Current and Input

Voltage, VOUT = 0.65 V, Auto Mode

Figure 9. Quiescent Current vs. Input Voltage

and Temperature VOUT = 0.4 V, Auto Mode

Figure 10. Shutdown Current vs. Input Voltage

and Temperature

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TYPICAL CHARACTERISTICS (continued)

Unless otherwise specified, VIN = 3.6 V, VOUT = 0.4 V, Auto Mode, TA = 25°C; circuit and components according to Figure 1 and Table 1.

Figure 11. Output Ripple, VIN = 3.6 V, VOUT = 0.65 V,

20 mA Load

Figure 12. Output Ripple, VIN = 3.6 V, VOUT = 0.65 V,

770 mA Load

Figure 13. Line Transient, VIN = 3.0 V @ 3.6 V, VOUT = 0.4 V,

10 ms Edge, 100 mA Load, Forced PWM Mode

Figure 14. Load Transient, VIN = 3.6 V, VOUT = 0.4 V,

10 mA @ 700 mA, 200 ns Edge, Auto Mode

Figure 15. Load Transient, VIN = 3.2 V, VOUT = 1.125 V,

0 mA @ 800 mA, 900 ns Edge, Auto Mode

Figure 16. Load Transient, VIN = 3.8 V, VOUT = 1.125 V,

0 mA @ 800 mA, 900 ns Edge, Auto Mode

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TYPICAL CHARACTERISTICS (continued)

Unless otherwise specified, VIN = 3.6 V, VOUT = 0.4 V, Auto Mode, TA = 25°C; circuit and components according to Figure 1 and Table 1.

Figure 17. Startup, VIN = 3.6 V, VOUT = 0.65 V, 200 mA Load,

with 5 ms EN Delay, Auto Mode

OPERATING DESCRIPTION

The FAN53528 is a step−down switching voltage

regulator that delivers a programmable output voltage from

an input voltage supply of 2.5 V to 5.5 V. Using a proprietary

architecture with synchronous rectification, the FAN53528

is capable of delivering 3.0 A at over 80% efficiency. The

regulator operates at a nominal frequency of 2.4 MHz at full

load, which reduces the value of the external components to

330 nH or 470 nH for the output inductor and 44 mF for the

output capacitor. High efficiency is maintained at light load

with single−pulse PFM.

An I2C−compatible interface allows transfers up to

3.4 Mbps. This communication interface can be used to:

•Dynamically re−program the output voltage in 6.25 mV

increments;

•Reprogram the mode to enable or disable PFM;

•Control voltage transition slew rate; or

•Enable/disable the regulator.

Control Scheme

The FAN53528 uses a proprietary non−linear,

fixed−frequency PWM modulator to deliver a fast load

transient response, while maintaining a constant switching

frequency over a wide range of operating conditions. The

regulator performance is independent of the output

capacitor ESR, allowing for the use of ceramic output

capacitors. Although this type of operation normally results

in a switching frequency that varies with input voltage and

load current, an internal frequency loop holds the switching

frequency constant over a large range of input voltages and

load currents.

For very light−loads, the FAN53528 operates in

Discontinuous Current Mode (DCM) single−pulse PFM,

which produces low output ripple compared with other PFM

architectures. Transition between PWM and PFM is

relatively seamless, providing a smooth transition between

DCM and CCM Modes.

PFM can be disabled by programming the MODE bits in

the CONTROL register in combination with the state of the

VSEL pin. See table in the Control Register 02h.

Enable and Soft−Start

When the EN pin is LOW; the IC is shut down, all internal

circuits are off, and the part draws very little current. In this

state, I2C can be written to or read from as long as input

voltage is above the UVLO. The registers keep the content

when the EN pin is LOW. The registers are reset to default

values during a Power On Reset (POR). When the

OUTPUT_DISCHARGE bit in the Control register is

enabled (logic HIGH) and the EN pin is LOW or the

BUCK_ENx bit is LOW, an 11 W load is connected from

VOUT to GND to discharge the output capacitors.

Raising EN while the BUCK_ENx bit is HIGH activates

the part and begins the soft−start cycle. For option EUC48X,

there is 5 ms delay time from EN HIGH to VOUT start

soft−start. And for options FAN53528BUC08X,

FAN53528GUC48X and FAN53528DUC40X, there is no

EN Delay. During soft−start, the modulator’s internal

reference is ramped slowly to minimize surge currents on the

input and prevent overshoot of the output voltage.

Synchronous rectification is inhibited, allowing the IC to

start into a pre−charged capacitive load.

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Figure 18. EN Delay

VOUT

0 V

1.8 V

EN_Delay

0 V

If large values of output capacitance are used, the

regulator may fail to start. The maximum COUT capacitance

for starting with a heavy constant−current load is

approximately:

COUTMAX [(ILMPK *ILOAD) 320m

VOUT

(eq. 1)

where COUTMAX is expressed in μF and ILOAD is the load

current during soft−start, expressed in A.

If the regulator is at its current limit for 16 consecutive

current limit cycles, the regulator shuts down and enters

tri−state before reattempting soft−start 1700 ms later. This

limits the duty cycle of full output current during soft−start

to prevent excessive heating.

The IC allows for software enable of the regulator, when

EN is HIGH, through the BUCK_EN bits. BUCK_EN0 and

BUCK_EN1 are both initialized HIGH. These options start

after a POR, regardless of the state of the VSEL pin.

Table 10. HARDWARE AND SOFTWARE ENABLE

Pins BITS

EN VSEL BUCK_EN0 BUCK_EN1 Output Mode

0 X X X OFF Shutdown

1 0 0 X OFF Shutdown

1 0 1 X ON Auto

1 1 X 0 OFF Shutdown

1 1 X 1 ON FPWM

VSEL Pin and I2C Programming Output Voltage

The output voltage is set by the NSELx control bits in

VSEL0 and VSEL1 registers. The output is given as:

VOUT +0.35 V )NSELx 6.25 mV (eq. 2)

For example, if NSEL =1010000 (80 decimal), then

VOUT = 0.35 + 0.5 = 0.85 V.

Output voltage can also be controlled by toggling the

VSEL pin LOW or HIGH. VSEL LOW corresponds to

VSEL0 and VSEL HIGH corresponds to VSEL1. Upon

POR, VSEL0 and VSEL1 are reset to their default voltages.

Transition Slew Rate Limiting

When transitioning from a low to high voltage, the IC can

be programmed for one of eight possible slew rates using the

SLEW bits in the Control register, as shown in Table 11.

Table 11. TRANSITION SLEW RATE

Decimal Bin Slew Rate

0 000 64.00 mV/ms

1 001 32.00 mV/ms

2 010 16.00 mV/ms

3 011 8.00 mV/ms

4 100 4.00 mV/ms

5 101 2.00 mV/ms

6110 1.00 mV/ms

7111 0.50 mV/ms

Transitions from high to low voltage rely on the output

load to discharge VOUT to the new set point. Once the

high−to−low transition begins, the IC stops switching until

VOUT has reached the new set point.

Under−Voltage Lockout (UVLO)

When EN is HIGH, the under−voltage lockout keeps the

part from operating until the input supply voltage rises

HIGH enough to properly operate. This ensures proper

operation of the regulator during startup or shutdown.

Input Over−Voltage Protection (OVP)

When VIN exceeds VSDWN (~ 6.2 V), the IC stops

switching to protect the circuitry from internal spikes above

6.5 V. An internal filter prevents the circuit from shutting

down due to noise spikes.

Current Limiting

A heavy load or short circuit on the output causes the

current in the inductor to increase until a maximum current

threshold is reached in the high−side switch. Upon reaching

this point, the high−side switch turns off, preventing high

currents from causing damage. 16 consecutive current limit

cycles in current limit, cause the regulator to shut down and

stay off for about 1700 ms before attempting a restart.

Thermal Shutdown

When the die temperature increases, due to a high load

condition and/or high ambient temperature, the output

switching is disabled until the die temperature falls

sufficiently. The junction temperature at which the thermal

shutdown activates is nominally 150°C with a 17°C

hysteresis.

Monitor Register (Reg05)

The Monitor register indicates of the regulation state of

the IC. If the IC is enabled and is regulating, its value is

(1000 0001).

I2C Interface

The serial interface is compatible with Standard, Fast,

Fast Plus, and HS Mode I2C BusR specifications. The SCL

line is an input and its SDA line is a bi−directional

open−drain output; it can only pull down the bus when

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active. The SDA line only pulls LOW during data reads and

when signaling ACK. All data is shifted in MSB (bit 7) first.

I2C Slave Address

In hex notation, the slave address assumes a 0 LS Bit. The

hex slave address is A0 for FAN53528BUCxxX and A4 for

FAN53528DUCxxX, FAN53528EUCxxX, and

FAN53528GUCxxX.

Table 12. I2C SLAVE ADDRESS

Option Hex

Bits

7 6 5 4 3 2 1 0

BUCxx A0 1 0 1 0 0 0 0 R/W

DUCxx,

EUCxx,

GUCxx

A4 1 0 1 0 0 1 0 R/W

Other slave addresses can be assigned. Contact an

ON Semiconductor representative.

Bus Timing

As shown in Figure 19 data is normally transferred when

SCL is LOW. Data is clocked in on the rising edge of SCL.

Typically, data transitions shortly at or after the falling edge

of SCL to allow sufficient time for the data to set up before

the next SCL rising edge.

ÎÎÎ

ÜÜÜ

SCL tSU

SDA

Data change allowed

Figure 19. Data Transfer Timing

Each bus transaction begins and ends with SDA and SCL

HIGH. A transaction begins with a START condition, which

is defined as SDA transitioning from 1 to 0 with SCL HIGH,

as shown in Figure 20.

SCL

tHD; STA

SDA Slave Address

MS Bit

Figure 20. START Bit

A transaction ends with a STOP condition, defined as

SDA transitioning from 0 to 1 with SCL high, as shown in

Figure 21.

SCL

SDA

Slave Releases Master Drives

ACK(0) or

NACK(1)

tHD;STO

Figure 21. STOP Bit

During a read from the FAN53528, the master issues a

REPEATED START after sending the register address and

before resending the slave address. The REPEATED

START is a 1 to 0 transition on SDA while SCL is HIGH, as

shown in Figure 22.

SCL

SDA ACK(0) or

NACK(1)

Slave Releases

SLADDR

MS Bit

tHD;STA

tSU;STA

Figure 22. REPEATED START Timing

High−Speed (HS) Mode

The protocols for High−Speed (HS), Low−Speed (LS),

and Fast−Speed (FS) Modes are identical; except the bus

speed for HS Mode is 3.4 MHz. HS Mode is entered when

the bus master sends the HS master code 00001XXX after

a START condition (Figure 20). The master code is sent in

Fast or Fast−Plus Mode (less than 1 MHz clock); slaves do

not ACK this transmission.

The master generates a REPEATED START condition

(Figure 22) that causes all slaves on the bus to switch to HS

Mode. The master then sends I2C packets, as described

above, using the HS Mode clock rate and timing.

The bus remains in HS Mode until a STOP bit (Figure 21)

is sent by the master. While in HS Mode, packets are

separated by REPEATED START conditions (Figure 22).

Read and Write Transactions

The following figures outline the sequences for data read

and write. Bus control is signified by the shading of the

packet, defined as:

•Master Drives Bus and

•Slave Drives Bus

All addresses and data are MSB first.

Table 13. I2C BIT DEFINITIONS FOR FIGURE 23 AND

FIGURE 24

Symbol Definition

SSTART, see Figure 20

PSTOP, see Figure 21

AACK. The slave drives SDA to 0

to acknowledge the preceding packet.

ANACK. The slave sends a 1 to NACK the pre-

ceding packet.

RREPEATED START, see Figure 22

FAN53528

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SSlave Address AReg Addr A A P0

7 bits 8 bits 8 bits

Data

000

Figure 23. Write Transaction

SSlave Address AReg Addr A0

7 bits 8 bits

RSlave Address

7 bits

1 A Data A

8 bits

00 01

Figure 24. Write Transaction Followed by a Read Transaction

Table 14. REGISTER MAP

Hex

Address Name Function Binary Hex

00 VSEL0 Controls VOUT settings when VSEL pin = LOW 1XXXXXXX XX

01 VSEL1 Controls VOUT settings when VSEL pin = HIGH 1XXXXXXX XX

02 CONTROL Determines whether VOUT output discharge is enabled and also the slew rate

of positive transitions

10000010 82

03 ID1 Read−only register identifies vendor and chip type 1000000181

04 ID2 Read−only register identifies die revision 00001000 08

05 MONITOR Indicates device status 00000000 00

Table 15. BIT DEFINITIONS

The following table defines the operation or each register bit. Bold indicates power−on default values.

Bit Name Type Value Description

VSEL0 Register Address: 00

7 BUCK_EN0 R/W 1 Software buck enable. When EN pin is LOW, the regulator is off. When EN

pin is HIGH, BUCK_EN bit takes precedent.

6:0 NSEL0 R/W XXX XXXX Sets VOUT value from 0.35 to 1.14375 V (see eq. 2).

VSEL1 Register Address: 01

7 BUCK_EN1 R/W 1 Software buck enable. When EN pin is LOW, the regulator is off. When EN

pin is HIGH, BUCK_EN bit takes precedent.

6:0 NSEL1 R/W XXX XXXX Sets VOUT value from 0.35 to 1.14375 V (see eq. 2).

CONTROL Register Address: 02

7OUTPUT_

DISCHARGE R/W

0When the regulator is disabled, VOUT is not discharged.

1When the regulator is disabled, VOUT discharges through an internal pull−

down.

6:4 SLEW R/W 000 –111 Sets the slew rate for positive voltage transitions (see Table 11)

3 Reserved 0Always reads back 0.

2 RESET R/W 0 Setting to 1 resets all registers to default values. Always reads back 0.

1:0 MODE R/W 10

In combination with the VSEL pin, these two bits set the operation of the

buck to be either in Auto−PFM/PWM Mode during light load or Forced

PWM mode. See table below.

Mode of Operation

VSEL Pin Binary Operation

Low X0 Auto PFM/PWM

Low X1 Forced PWM

High 0X Auto PFM/PWM

High 1X Forced PWM

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Table 15. BIT DEFINITIONS (continued)

The following table defines the operation or each register bit. Bold indicates power−on default values.

Bit DescriptionValueTypeName

ID1 Register Address: 03

7:5 VENDOR R 100 Signifies ON Semiconductor as the IC vendor.

4 Reserved R 0 Always reads back 0.

3:0 DIE_ID R 0001 DIE ID

ID2 Register Address: 04

7:4 Reserved R 0000 Always reads back 0000.

3:0 DIE_REV R 1000 FAN53528 Die Revision

MONITOR Register Address: 05

7 PGOOD R 0 1: Buck is enabled and soft−start is completed.

6 UVLO R 0 1: Signifies the VIN is less than the UVLO threshold.

5 OVP R 0 1: Signifies the VIN is greater than the OVP threshold.

4 POS

R 0 1: Signifies a positive voltage transition is in progress and the output

voltage has not yet reached its new setpoint. This bit is also set during IC

soft−start.

3 NEG R 0 1: Signifies a negative voltage transition is in progress and the output

voltage has not yet reached its new setpoint.

2 RESET_STAT R 0 1: Indicates that a register reset was performed. This bit is cleared after

1 OT R 0 1: Signifies the thermal shutdown is active.

0 BUCK_STATUS R 0 1: Buck enabled; 0: buck disabled.

APPLICATION INFORMATION

Selecting the Inductor

The output inductor must meet both the required

inductance and the energy−handling capability of the

application. The inductor value affects the average current

limit, the output voltage ripple, and the efficiency.

The ripple current (ΔI) of the regulator is:

DI[

VOUT

VIN

ǒVIN*VOUT

L fSW Ǔ(eq. 3)

The maximum average load current, IMAX(LOAD), is

related to the peak current limit, ILIM(PK), by the ripple

current such that:

IMAX(LOAD) +ILIM(PK)*DI

2(eq. 4)

The FAN53528 is optimized for operation with

L=330 nH, but is stable with inductances up to 1.0 μH

(nominal). The inductor should be rated to maintain at least

80% of its value at ILIM(PK). Failure to do so decreases the

amount of DC current the IC can deliver.

Efficiency is affected by the inductor DCR and inductance

value. Decreasing the inductor value for a given physical

size typically decreases the DCR; but since ΔI increases, the

RMS current increases, as do core and skin−effect losses:

IRMS +IOUT(DC)

2)DI2

Ǹ(eq. 5)

The increased RMS current produces higher losses

through the RDS(ON) of the IC MOSFETs and the inductor

ESR.

Increasing the inductor value produces lower RMS

currents, but degrades transient response. For a given

physical inductor size, increased inductance usually results

in an inductor with lower saturation current.

Table 16. EFFECTS OF INDUCTOR VALUE (FROM

330 nH RECOMMENDED) ON REGULATOR

PERFORMANCE

IMAX(LOAD) DVOUT (eq. 7) Transient Response

Increase Decrease Degraded

Inductor Current Rating

The current−limit circuit can allow substantial peak

currents to flow through L1 under worst−case conditions. If

it is possible for the load to draw such currents, the inductor

should be capable of sustaining the current or failing in a safe

manner.

For space−constrained applications, a lower current rating

for L1 can be used. The FAN53528 may still protect these

inductors in the event of a short circuit, but may not be able

to protect the inductor from failure if the load is able to draw

higher currents than the DC rating of the inductor. Refer to

Table 2 for the recommended inductors.

FAN53528

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Output Capacitor and VOUT Ripple

If space is at a premium, 0603 capacitors may be used.

Increasing COUT has negligible effect on loop stability

and can be increased to reduce output voltage ripple or to

improve transient response. Output voltage ripple, DVOUT,

is calculated by:

DVOUT +DILƪfSW COUT ESR2

2 D (1 *D) )1

8 fSW COUTƫ(eq. 6)

where COUT is the effective output capacitance.

The capacitance of COUT decreases at higher output

voltages, which results in higher DVOUT. Equation 6 is only

valid for CCM operation, which occurs in PWM Mode.

The FAN53528 can be used with either 2 x 22 mF (0603)

or 2 x 47 mF (0603) output capacitor configuration. If a

tighter ripple and transient specification is need from the

FAN53528, then the 2 x 47 mF is recommended.

The lowest DVOUT is obtained when the IC is in PWM

Mode and, therefore, operating at 2.4 MHz. In PFM Mode,

fSW is reduced, causing DVOUT to increase.

ESL Effects

The Equivalent Series Inductance (ESL) of the output

capacitor network should be kept low to minimize the

square−wave component of output ripple that results from

the division ratio COUT ESL and the output inductor (LOUT).

The square−wave component due to the ESL can be

estimated as:

DVOUT(SQ) [VIN

ESLCOUT

L1 (eq. 7)

A good practice to minimize this ripple is to use multiple

output capacitors to achieve the desired COUT value. For

example, to obtain COUT=20 mF, a single 22 mF 0805 would

produce twice the square wave ripple as two × 10 mF 0805.

To minimize ESL, try to use capacitors with the lowest

ratio of length to width. 0805 s have lower ESL than 1206 s.

If low output ripple is a chief concern, some vendors

produce 0508 capacitors with ultra−low ESL. Placing

additional small−value capacitors near the load also reduces

the high−frequency ripple components.

Input Capacitor

The ceramic input capacitors should be placed as close as

possible between the VIN and PGND pins to minimize the

parasitic inductance. If a long wire is used to bring power to

the IC, additional “bulk” capacitance (electrolytic or

tantalum) should be placed between CIN and the power

source lead to reduce under−damped ringing that can occur

between the inductance of the power source leads and CIN.

The effective CIN capacitance value decreases as VIN

increases due to DC bias effects. This has no significant

impact on regulator performance.

Thermal Considerations

Heat is removed from the IC through the solder bumps to

the PCB copper. The junction−to−ambient thermal

resistance (θJA) is largely a function of the PCB layout (size,

copper weight, and trace width) and the temperature rise

from junction to ambient (ΔT).

For the FAN53528, θJA is 42°C/W when mounted on its

four−layer with vias evaluation board in still air with 2 oz.

outer layer copper weight and 1 oz. inner layer.

For long−term reliable operation, the junction

temperature (TJ) should be maintained below 125°C.

To calculate maximum operating temperature (<125°C)

for a specific application:

1. Use efficiency graphs to determine efficiency for

the desired VIN, VOUT, and load conditions.

2. Calculate total power dissipation using:

PT+VOUT ILOAD ǒ1

h*1Ǔ(eq. 8)

3. Estimate inductor copper losses using:

PL+ILOAD

2 DCRL(eq. 9)

4. Determine IC losses by removing inductor losses

(step 3) from total dissipation:

PIC +PT*PL(eq. 10)

5. Determine device operating temperature:

DT+PIC QJA TIC +TA)DT(eq. 11)

and

note that the RDS(ON) of the power MOSFETs increases

linearly with temperature at about 1.4%/°C. This causes the

efficiency (η) to degrade with increasing die temperature.

Layout Recommendations

1. The input capacitor (CIN) should be connected as

close as possible to the VIN and GND pins.

Connect to VIN and GND using only top metal.

Do not route through vias.

2. Place the inductor (L) as close as possible to the

IC. Use short wide traces for the main current

paths.

3. The output capacitor (COUT) should be placed as

close as possible to the IC. Connection to GND

should be on top metal. Feedback signal

connection to VOUT should be routed away from

noisy components and traces (e.g. SW line). For

remote sensing application, place one or all output

capacitors near the load and if there are also output

capacitors placed near the inductor, the maximum

trace resistance between the inductor and the load

should not exceed 30 mW.

FAN53528

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Figure 25. Guidance for Layer 1

Figure 26. Layer 2 Figure 27. Layer 3

FAN53528

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Figure 28. Layer 4

SDA

SCL

VSEL

FAN53528

VIN

VOUT

PGND

AGND

CIN1

GND

VDD

Core

Processor

(System Load)

1. Feedback trace connects to “+” side of the output capacitor.

2. For remote sensing, place one or all output

capacitors near the load.

3. If there are also output capacitors placed near the inductor, the maximum trace resistance between

the inductor and the load should not exceed 30 mW.

CBY

COUT COUT_LOAD

Figure 29. Remote Sensing Schematic

Table 17. PRODUCT SPECIFIC DIMENSIONS

DE X Y

2.015 ± 0.03 mm 1.310 ± 0.03 mm 0.255 mm 0.2075 mm

ON Semiconductor is licensed by Philips Corporation to carry the I2C Bus Protocol.

ARM is a registered trademark of ARM Limited (or its subsidiaries) in the EU and/or elsewhere.

Tegra is a trademark of NVIDIA Corporation.

OMAP is a trademark and brand of Texas Instruments Incorporated.

NovaThor is a trademark of ST−Ericsson.

ARMADA is a trademark of Emergency Technology, Inc.

Krait is a trademark of Qualcomm Incorporated.

WLCSP15 2.015x1.31x0.586

CASE 567QS

ISSUE O DATE 31 OCT 201

MECHANICAL CASE OUTLINE

PACKAGE DIMENSIONS

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October, 2002 − Rev. 0 Case Outline Number:

XXX

DOCUMENT NUMBER:

STATUS:

NEW STANDARD:

DESCRIPTION:

98AON13347G

ON SEMICONDUCTOR STANDARD

WLCSP15 2.015x1.31x0.586

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DUCTOR. REQ. BY F. ESTRADA. 31 OCT 2016

October, 2016 − Rev. O Case Outline Number

567QS

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