RT7272BGSP - Richtek Technology - Datasheet.Directory

RT7272B

DS7272B-07 February 2018 www.richtek.com

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Design

Ordering Information

Note :

Richtek products are :

` RoHS compliant and compatible with the current require-

ments of IPC/JEDEC J-STD-020.

` Suitable for use in SnPb or Pb-free soldering processes.

3A, 36V, 500kHz Synchronous Step-Down Converter

General Description

The RT7272B is a high efficiency, current mode

synchronous step-down DC/DC converter that can deliver

up to 3A output current over a wide input voltage range

from 4.5V to 36V. The device integrates a 150mΩ high

side and a 80mΩ low side MOSFET to achieve high

conversion efficiency up to 95%. The current mode control

architecture supports fast tran sient response and simple

compensation circuit.

A cycle-by-cycle current limit function provides protection

against shorted output and an internal soft-start eliminates

input current surge during start-up. The RT7272B provides

complete protection functions such a s input under-voltage

lockout, output under-voltage protection, over-current

protection and thermal shutdown.

The RT7272B is available in the thermal enhanced SOP-8

(Exposed Pad) pa ckage.

Features

z4.5V to 36V Input Voltage Range

z3A Output Current

zInternal N-MOSFET s

zCurrent Mode Control

zFixed Frequency Operation : 500kHz

zAdjustable Output Voltage from 0.8V to 30V

zHigh Efficiency Up to 95%

zStable with Low ESR Ceramic Output Capacitors

zCycle-by-Cycle Current Limit

zInput Under-Voltage Lockout

zOutput Under-Voltage Protection

zThermal Shutdown Protection

zAdjustable Current Limit

zPower Saving Mode for High Efficiency at Light

Load

zRoHS Compliant and Halogen Free

Applications

zDistributed Power Systems

zPre-Regulator for Linear Regulators

zNotebook Computers

zPoint of Load Regulator in Distributed Power Syste m

zDigital Set-top Boxes

zPersonal Digital Recorders

zBroadband Communications

zFlat Pa nel TVs a nd Monitors

zVehicle Electronics

Simplified Application Circuit

Package Type

SP : SOP-8 (Exposed Pad-Option 2)

T7272B

Lead Plating System

G : Green (Halogen Free and Pb Free

)

VIN

GND

BOOT

SW L

VOUT

VIN

RT7272B

RLIM

RLCOMP CCRC

CIN

COUT

Enable

RT7272B

2DS7272B-07 February 2018www.richtek.com

Functional Pin Description

Function Block Diagram

Pin Configurations

(TOP VIEW)

SOP-8 (Exposed Pad)

Marking Information

BOOT

GND

VIN

RLIM

COMP

GND

RT7272BGSP : Product Number

YMDNN : Date Code

Pin No. Pin Name

Pin Func tion

1 SW Switch Node Connect to external L-C filter.

2 BOOT

Bootstrap Supply for High Side Gate Drive. A 100nF or greater capacitor is

recom mended to connect from BOOT pin to SW pin.

3 EN Enable Control I nput. A logic-high enables the converter; a logic -low forces the

d evi ce i nto shu tdow n mode.

9 (Expo sed Pad)

GND Ground. The exposed pad must be soldered to a large PCB and connected to

GND for maximum thermal dissipation.

5 FB Feedback Input. This pin is connected to the converter output . It is used to set

the output of the converter to regulate to the desired value via an resistive

divider.

6 COMP

Compensation Node. COMP is used to compensate the regulation control loop.

Connec t a ser ie s RC networ k from CO MP to GND . In some case s, an addition al

c ap aci tor fr om CO MP to GND is requ ir ed.

7 RLIM Current L imit Setting. Connec t to a resistor to d etermine current limit.

8 VIN Power Input. The input voltage range is from 4.5V to 36V. Must bypass with a

su itable larg e ceramic capacitor.

Comparator

Oscillator

Foldback

Control

0.4V

Internal

Regulator

1.7V

Shutdown

Comparator

Current Sense

Amplifier

BOO

GND

COMP

VAVCC Slope Comp

Current

Comparator

-EA

0.8V

RLIM

1.2V

Lockout

Comparator

VCC

80m

Ω

150m

Ω

RSENSE

Ω

VCC

RT7272B

GSPYMDNN

RT7272B

DS7272B-07 February 2018 www.richtek.com

Operation

The RT7272B is a constant frequency, current mode

synchronous step-down converter. In normal operation,

the high side N-MOSFET is turned on when the S-R latch

is set by the oscillator a nd is turned of f when the current

comparator resets the S-R latch. While the high side

N-MOSFET is turned off, the low side N-MOSFET is turned

on to conduct the inductor current until next cycle begins.

Error Amplifier

The error a mplifier adjusts its output voltage by comparing

the feedback signal (VFB) with the internal 0.8V reference.

When the load current increase s, it causes a drop in the

feedback voltage relative to the reference. The error

a mplifier's output voltage then rises to allow higher inductor

current to match the load current.

Oscillator

The internal oscillator runs at fixed frequency 500kHz. In

short circuit condition, the frequency is reduced to 75kHz

for low power consumption.

Internal Regulator

The regulator provides low voltage power to supply the

internal control circuits and the bootstrap power for high

side gate driver .

Enable

The converter is turned on when the EN pin is higher than

2V . When the EN pin is lower than 0.4V, the converter will

enter shutdown mode and reduce the supply current to

0.5µA.

Soft-Start (SS)

An internal current source charges an internal capacitor

to build a soft-start ra mp voltage. The FB voltage will track

the internal ramp voltage during soft-start interval. The

typical soft-start time is 2ms.

Current Setting

The current limit of high side MOSFET is adjustable by

an external resistor connected to the RLIM pin. The current

limit ra nge is from 1.9A to 7A. When the inductor current

reaches the current limit threshold, the COMP voltage

will be clamped to limit the inductor current.

UV Comparator

If the feedback voltage (VFB) is lower than 0.4V, the UV

Comparator will go high to turn off the high side MOSFET.

The output under voltage protection is designed to operate

in Hiccup mode. When the UV condition is removed, the

converter will resume switching.

Thermal shutdown

The over temperature protection function will shut down

the switching operation when the junction temperature

exceeds 150°C. Once the junction temperature cools

down by approximately 20°C, the converter will

automatically resume switching.

RT7272B

4DS7272B-07 February 2018www.richtek.com

Electrical Characteristics

(VIN = 12V, CIN = 20µF, TA = 25°C, unless otherwise specified)

Absolute Maximum Ratings (Note 1)

zSupply Input V oltage, VIN ----------------------------------------------------------------------------------------- −0.3V to 40V

zSwitch Voltage, SW ------------------------------------------------------------------------------------------------ −0.3V to (VIN + 0.3V)

zVBOOT − VSW ---------------------------------------------------------------------------------------------------------- −0.3V to 6V

z Other Pins Voltage -------------------------------------------------------------------------------------------------- −0.3V to 40V

zPower Dissipation, PD @ TA = 25°C

SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------- 2.041W

zPa ckage Thermal Re sistance (Note 2)

SOP-8 (Exposed Pad), θJA ---------------------------------------------------------------------------------------- 49°C/W

SOP-8 (Exposed Pad), θJC --------------------------------------------------------------------------------------- 15°C/W

zLead T emperature (Soldering, 10 sec.)------------------------------------------------------------------------- 26 0°C

zJunction T emperature----------------------------------------------------------------------------------------------- 150°C

zStorage T emperature Range -------------------------------------------------------------------------------------- −65°C to 150°C

zESD Susceptibility (Note 3)

HBM (Human Body Model)---------------------------------------------------------------------------------------- 2kV

Recommended Operating Conditions (Note 4)

zSupply Input V oltage, VIN ----------------------------------------------------------------------------------------- 4.5V to 36V

zJunction T emperature Range-------------------------------------------------------------------------------------- −40°C to 125°C

zAmbient T emperature Range-------------------------------------------------------------------------------------- −40°C to 85°C

Parameter Symbol Test Conditions Min Typ Max

Unit

Shutdown Suppl y Current VEN = 0V -- 0.5 3 µA

Quiescent Current IQ V

EN = 3V, VFB = 0.9V -- 0.9 1.2 mA

Feedback Referenc e

Voltage VREF 4.5V ≤ VIN ≤ 36V 0.788

0.8 0.812

High Side Switch

On-Resistance RDS(ON)1 -- 150 -- mΩ

Low Side Switch

On-Resistance RDS(ON)2 -- 80 -- mΩ

High Side Switc h Leakage

Current V

EN = 0V, VSW = 0V -- 0 10 µA

Upper Switch Curr ent Limit

Range UOC 1.9 -- 7 A

Upper Switch Curr ent Limit

UOC

(Not e 5)

Min. Duty Cycle, RLIM = 57.6kΩ 1.9 2.5 3.1

Min. Duty Cycle, RLIM = 84.5kΩ 2.7 3.5 4.2

Min. Duty Cycle, RLIM = 137kΩ 4.5 5.5 6.5

Lower Switch Curr ent Limit

From Drain to Source -- 1.5 -- A

RT7272B

DS7272B-07 February 2018 www.richtek.com

Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are

stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in

the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may

affect device reliability.

Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is

measured at the exposed pad of the package.

Note 3. Devices are ESD sensitive. Handling precaution is recommended.

Note 4. The device is not guaranteed to function outside its operating conditions.

Note 5. RLIM (kΩ) = [UOC x 24.14 x (1 + 0.024 x (UOC − 3.5)) − 1.3], where UOC is desired upper switch peak current limit

value.

Parameter Symbol Test Conditions Min Typ Max Unit

Oscillation Frequency fOSC1 450 500 550 kHz

Short Circuit O scill ation

Frequency fOSC2 V

FB = 0V -- 75 -- kHz

Maximum Duty Cycle DMAX V

FB = 0.7V -- 90 -- %

Mi nimum On-T ime tON -- 100 -- ns

EN I nput Voltage Logic-High

VIH 2 -- --

Logic-Low VIL -- -- 0.4

Input Under Voltage Lockout

Thres hold VUVLO V

IN Rising 3.9 4.1 4.3 V

Input Under Voltage Lockout

Hysteresis ∆VUVLO -- 250 -- mV

Thermal Shutdown TSD -- 150

-- °C

Thermal Shutdown Hyster esis ∆TSD -- 20

-- °C

COMP to Current Sense

Trans conductance GCS ∆ICOMP = ±10µA -- 4.7 -- A/V

Error A mp lifier

T rans conductance GEA -- 1000

-- µA/V

Load Regul ation ∆VLOAD -- -- 0.05

%/A

Li ne Regulation ∆VLINE V

IN = 4.5V to 36V -- -- 0.1 %

RT7272B

6DS7272B-07 February 2018www.richtek.com

Typical Application Circuit

Table 1. Suggested Component Values

VOUT (V) R1 (kΩ) R2 (kΩ) RC (kΩ) L (µH) CC (nF) COUT (µF)

12 47 3.35 47 10 2.7 22 x 2

8 27 3 36 8.2 2.7 22 x 2

5 62 11.8 24 6.8 2.7 22 x 2

3.3 75 24 16 4.7 2.7 22 x 2

2.5 25.5 12 12 3.6 2.7 22 x 2

1.2 30 60 6.8 2.2 2.7 22 x 2

VIN

GND

BOOT

100nF

VOUT

10µF x 2

VIN

4.5V to 36V

RT7272B

RLIM

COMP CCRC

4, 9 (Exposed Pad)

CIN

137k

COUT

RLIM

Enable

RT7272B

DS7272B-07 February 2018 www.richtek.com

Typical Operating Characteristics

Efficiency vs. Output Current

100

0 0.5 1 1.5 2 2.5 3

Output Current (A)

Effi ciency (% )

VIN = 4.5V

VIN = 12V

VIN = 24V

VIN = 36V

VOUT = 3.3V

Reference vs . Te m pe rature

0.790

0.795

0.800

0.805

0.810

-50 -25 0 25 50 75 100 125

Temperatur e (°C)

Refer ence Voltage (V)

VOUT = 3.3V, IOUT = 0.3A

VIN = 4.5V

VIN = 12V

VIN = 24V

VIN = 36V

Efficiency vs. Output Current

100

0.01 0.1

Output Current (A)

Effi ciency (%)

VOUT = 3.3V

VIN = 4.5V

VIN = 12V

VIN = 24V

VIN = 36V

Output Voltage vs. Output Current

3.29

3.30

3.31

3.32

3.33

3.34

3.35

3.36

3.37

3.38

00.511.522.53

Output Current (A)

Output Vol tage (V)

VOUT = 3.3V, IOUT = 0.1A to 3A

VIN = 4.5V

VIN = 12V

VIN = 24V

VIN = 36V

Switching Frequency vs. Input Voltage

450

455

460

465

470

475

480

485

490

495

500

4 8 12 16 20 24 28 32 36

Input Vo ltage (V)

Swit ching Frequency (kHz) 1

VOUT = 3.3V, IOUT = 0.3A

Reference Voltage vs . Input Voltage

0.790

0.793

0.795

0.798

0.800

0.803

0.805

0.808

0.810

2 9.6 17.2 24.8 32.4 40

In put Voltage(V)

Reference Volt age(V)

VIN = 4.5V to 36V, VOUT = 3.3V, IOUT = 0.3A

RT7272B

8DS7272B-07 February 2018www.richtek.com

Time (1µs/Div)

Switching

VOUT

(5mV/Div)

VSW

(5V/Div)

(2A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 3A

Time (250µs/Div)

Load Transient Response

VOUT

(200mV/Div)

IOUT

(2A/Div)

VIN = 12V, VOUT = 3.3V, IOUT = 0.3A to 3A

Time (250µs/Div)

Load Transient Response

VOUT

(200mV/Div)

IOUT

(2A/Div)

VIN = 12V, VOUT = 3.3V, IOUT = 1.5A to 3A

Current Lim it vs . Te m pe rature

-50 -25 0 25 50 75 100 125

Temperatur e (°C)

Current Limit (A)

VIN = 12V

Switching Frequency vs. Temperature

440

450

460

470

480

490

500

-50 -25 0 25 50 75 100 125

Temperatur e (°C)

Swit ching Frequency (kHz) 1

VOUT = 3.3V, IOUT = 0.3A

VIN = 4.5V

VIN = 12V

VIN = 24V

VIN = 36V

Time (1µs/Div)

Switching

VOUT

(5mV/Div)

VSW

(5V/Div)

(1A/Div) VIN = 12V, VOUT = 3.3V, IOUT = 1.5A

RT7272B

DS7272B-07 February 2018 www.richtek.com

Time (2.5ms/Div)

Power On from EN

VOUT

(2V/Div)

VEN

(5V/Div)

IOUT

(2A/Div)

VIN = 12V, VOUT = 3.3V, IOUT = 3A

Time (2.5ms/Div)

Power Off from EN

VOUT

(2V/Div)

VIN

(5V/Div)

IOUT

(2A/Div)

VIN = 12V, VOUT = 3.3V, IOUT = 3A

RT7272B

10 DS7272B-07 February 2018www.richtek.com

Under Voltage Protection

Hiccup Mode

The RT7272B provides Hiccup Mode Under Voltage

Protection (UVP). When the VFB voltage drops below 0.4V ,

the UVP function will be triggered to shut down switching

operation. If the UVP condition remains for a period, the

RT7272B will retry automatically . When the UVP condition

is removed, the converter will resume operation. The UVP

is disabled during soft-start period.

Application Information

Output Voltage Setting

The resistive divider allows the FB pin to sense the output

voltage a s shown in Figure 1.

Figure 1. Output Voltage Setting

The output voltage is set by a n external resistive voltage

divider a ccording to the following equation :

OUT REF

V = V 1







Where VREF is the reference voltage (0.8V typ.).

External Bootstrap Diode

Connect a 0.1µF low ESR cera mic ca pacitor between the

BOOT and SW pins. This ca pacitor provides the gate driver

voltage for the high side MOSFET.

It is recommended to add an external bootstrap diode

between an external 5V and BOOT pin for efficiency

improvement when input voltage is lower than 5.5V or duty

ratio is higher than 65% .The bootstrap diode can be a

low cost one such as IN4148 or BA T54. The external 5V

ca n be a 5V fixed input from system or a 5V output of the

RT7272B. Note that the external boot voltage must be

lower than 5.5V

Figure 2. External Bootstra p Diode

Chip Enable Operation

The EN pin is the chip enable input. Pulling the EN pin

low (<0.4V) will shutdown the device. During shutdown

mode, the RT7272B quiescent current drops to lower than

3µA. Driving the EN pin high (>2V, <36V) will turn on the

device again. For external ti ming control, the EN pin ca n

also be externally pulled high by adding a REN resistor

a nd CEN ca pa citor from the VIN pin (see Figure 3).

An external MOSFET ca n be added to i mplement digital

control on the EN pin when no system voltage above 2.5V

is available, as shown in Figure 4. In this case, a 100kΩ

pull-up resistor, R EN, is connected between VIN and the

EN pin. MOSFET Q1 will be under logic control to pull

down the EN pin.

Figure 3. Enable Timing Control

Figure 4. Digital Ena ble Control Circuit

RT7272B

GND

VOUT

BOOT

RT7272B 100n

RT7272B

GND

IN REN

CEN

RT7272B

GND

100k

REN

RT7272B

DS7272B-07 February 2018 www.richtek.com

OUT OUT

LIN

I = 1

fL V

 

∆×−

 

 

Having a lower ripple current reduces not only the ESR

losses in the output ca pacitors but also the output voltage

ripple. High frequency with small ripple current can achieve

the highest efficiency operation. However, it requires a

large inductor to a chieve this goal.

For the ripple current selection, the value of ∆IL = 0.24(IMAX)

will be a reasonable starting point. The largest ripple

current occurs at the highest VIN. To guarantee that the

ripple current stays below the specified maximum, the

inductor value should be chosen according to the following

equation :

Table 2. Suggested Inductors for Typical

Application Circuit

Componen t

Supplier Series Dimensions

(mm)

TDK VLF10045

10 x 9.7 x 4.5

TDK SLF12565

12. 5 x 12.5 x 6.5

TAIYO

YUD EN N R 8 040 8 x 8 x 4

OUT OUT

(MAX) IN(MAX)

f0.24I V



×−



××



The inductor's current rating (caused a 40°C temperature

rising from 25°C ambient) should be greater than the

maximum load current and its saturation current should

be greater than the short circuit peak current limit. Plea se

see Ta ble 2 for the inductor selection reference.

Figure 5. Hiccup Mode U nder Voltage Protection

Time (50ms/Div)

Hiccup Mode

VOUT

(2V/Div)

ILX

(2A/Div)

IOUT = Short

Over Temperature Protection

The RT7272B features an Over Temperature Protection

(OTP) circuitry to prevent from overheating due to

excessive power dissipation. The OTP will shut down

switching operation when junction temperature exceeds

150°C. Once the junction temperature cools down by

a pproximately 20°C, the converter will resume operation.

To maintain continuous operation, the maximum junction

temperature should be lower than 125°C.

Inductor Selection

The inductor value and operating frequency determine the

ripple current according to a specific input and output

voltage. The ripple current ∆IL increases with higher VIN

and decrea ses with higher inductance.

OUT IN

RMS OUT(MAX) IN OUT

I = I 1

−

CIN and COUT Selection

The input capacitance, CIN, is needed to filter the

trapezoidal current at the Source of the high side MOSFET .

To prevent large ripple current, a low ESR input ca pacitor

sized for the maximum RMS current should be used. The

a pproxi mate RMS current equation is given :

This formula has a maximum at VIN = 2VOUT, where

IRMS = IOUT / 2. This simple worst case condition is

commonly used for design because even significant

deviations do not offer much relief.

Choose a capacitor rated at a higher temperature than

required. Several capacitors may also be paralleled to

meet size or height requirements in the design.

For the input capacitor, two 10µF low ESR ceramic

capacitors are suggested. For the suggested capacitor,

please refer to Ta ble 3 for more details.

The selection of COUT is determined by the required ESR

to minimize voltage ripple.

Moreover, the amount of bulk capacitance is also a key

for COUT selection to ensure that the control loop is stable.

Loop stability can be checked by viewing the load transient

response as described in a later section.

The output ripple, ∆VOUT , is determined by :

OUT L

OUT

VIESR

8fC



∆≤∆ +





RT7272B

12 DS7272B-07 February 2018www.richtek.com

Figure 7. Derating Curve of Maximum Power Dissipation

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

0 25 50 75 100 125

Ambient Tem pera ture (°C)

Power Dissi pation (W )

Copper Area

70mm2

50mm2

30mm2

10mm2

Min.Layout

Four-Layer PCB

The output ripple will be the highest at the maximum input

voltage since ∆IL increases with input voltage. Multiple

capa citors pla ced in parallel may be needed to meet the

ESR and RMS current handling requirement. Higher values,

lower cost cera mic capacitors are now becoming available

in smaller case sizes. Their high ripple current, high voltage

rating and low ESR make them ideal for switching regulator

applications. However, care must be taken when these

ca pa citors are used at input a nd output. When a ceramic

capacitor is used at the input and the power is supplied

by a wall adapter through long wires, a load step at the

output can induce ringing at the input, VIN. At best, this

ringing ca n couple to the output and be mista ken a s loop

instability. At worst, a sudden inrush of current through

the long wires can potentially cause a voltage spike at

VIN large enough to da mage the part.

Thermal Considerations

For continuous operation, do not exceed the maximum

operation junction temperature 125°C. The maximum

power dissipation depends on the thermal resistance of

IC pa ckage, PCB layout, the rate of surroundings airflow

and temperature difference between junction to a mbient.

The maximum power dissipation can be calculated by

following formula :

PD(MAX) = (TJ(MAX) − TA ) / θJA

Where TJ(MAX) is the maximum operation junction

temperature , TA is the a mbient temperature and the θJA is

the junction to ambient thermal resistance.

For recommended operating conditions specification of

RT7272B, the maximum junction temperature is 125°C.

The junction to ambient thermal resistance θJA is layout

dependent. For SOP-8 (Exposed Pad) package, the

thermal resistance θJA is 75°C/W on the standard JEDEC

51-7 four-layers thermal test board. The maximum power

dissipation at TA = 25°C can be calculated by following

formula :

PD(MAX) = (125°C − 25°C) / (75°C/W) = 1.333W

(min.copper area PCB layout)

PD(MAX) = (125°C − 25°C) / (49°C/W) = 2.04W

(70mm2copper area PCB layout)

The thermal resistance θJA of SOP-8 (Exposed Pad) is

determined by the package architecture design and the

PCB layout design. However, the package architecture

design had been designed. If possible, it's useful to

increa se thermal perf ormance by the PCB layout copper

design. The thermal resistance θJA c a n be decre ased by

adding copper area under the exposed pad of SOP-8

(Exposed Pad) pa ckage.

As shown in Figure 6, the a mount of copper area to which

the SOP-8 (Exposed Pad) is mounted affects thermal

performance. When mounted to the standard

SOP-8 (Exposed Pad) pad (Figure 6.a), θJA is 75°C/W.

Adding copper area of pad under the SOP-8 (Exposed

Pad) (Figure 6.b) reduces the θJA to 64°C/W . Even further,

increasing the copper area of pad to 70mm2 (Figure 6.e)

reduces the θJA to 49°C/W.

The maximum power dissipation depends on operating

ambient temperature for fixed TJ(MAX) and thermal

resistance θJA. The Figure 7 of derating curves allows the

designer to see the ef fect of rising ambient temperature

on the maximum power dissipation allowed.

RT7272B

DS7272B-07 February 2018 www.richtek.com

(a) Copper Area = (2.3 x 2.3) mm2, θJA = 75°C/W

(b) Copper Area = 10mm2, θJA = 64°C/W

(d) Copper Area = 50mm2 , θJA = 51°C/W

(e) Copper Area = 70mm2 , θJA = 49°C/W

Figure 6. Thermal Resistance vs. Copper Area Layout

Design

Layout Considerations

For best performance of the RT7272B, the following layout

guidelines must be strictly followed.

`Input capacitor must be placed as close to the IC as

possible.

`SW should be connected to inductor by wide and short

trace. Keep sensitive components away from this trace.

`The RL resistor, compensator and feedba ck components

must be connected as close to the device a s possible.

RT7272B

14 DS7272B-07 February 2018www.richtek.com

Table 3. Suggested Capacitors for CIN and COUT

Location Component Supplier

Part No. Capacitance (µF)

Case Siz e

CIN MURATA GRM32ER71H475K 4.7 1206

CIN TAIYO YUDEN UMK325BJ475MM-T 4.7 1206

CIN TDK C3225X5R1E106K 10 1206

CIN TAIYO YUDEN TMK316BJ106ML 10 1206

COUT MURATA GRM31CR60J476M 47 1206

COUT TDK C3225X5R0J476M 47 1210

COUT MURATA GRM32ER71C226M 22 1210

COUT TDK C3225X5R1C22M 22 1210

Figure 8. PCB Layout Guide

VOUT

BOOT

GND

VIN

RLIM

COMP

GND

CIN

COUT

CS*

RS*

CBOOT

VOUT

VIN CCRC

VIN

GND

The Compensator and feedback

components must be connected as

close to the device as possible.

Input capacitor must be placed

as close to the IC as possible.

W should be connected to

nductor by wide and short trace.

eep sensitive components

way from this trace and CBOOT.

The REN component

must be connected.

The RL resistor must be connecte

as close to the device as possible

Keep sensitive components away.

REN

* : Option

RT7272B

DS7272B-07 February 2018 www.richtek.com

Richtek Technology Corporation

14F, No. 8, Tai Yuen 1st Street, Chupei City

Hsinchu, Taiwan, R.O.C.

Tel: (8863)5526789

Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should

obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot

assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be

accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third

parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.

Outline Dimension

EXPOSED THERMAL PAD

(Bottom of Package)

8-Lead SOP (Exposed Pad) Plastic Package

Dimensions In Millimeters

Dimensions In Inches

Symbol Min Max Min Max

A 4.801 5.004 0.189 0.197

B 3.810 4.000 0.150 0.157

C 1.346 1.753 0.053 0.069

D 0.330 0.510 0.013 0.020

F 1.194 1.346 0.047 0.053

H 0.170 0.254 0.007 0.010

I 0.000 0.152 0.000 0.006

J 5.791 6.200 0.228 0.244

M 0.406 1.270 0.016 0.050

X 2.000 2.300 0.079 0.091

Option 1

Y 2.000 2.300 0.079 0.091

X 2.100 2.500 0.083 0.098

Option 2

Y 3.000 3.500 0.118 0.138