Richtek RT7291AGQUF, RT7291BGQUF Schematic [ru]

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RT7291A/B

6A, 23V, 500kHz, ACOTTM Synchronous Buck Converter with LDO for System 5V

General Description

The RT7291A/B is a synchronous Buck converter with Advanced Constant On-Time (ACOTTM) mode control. The main control loop of RT7291A/B uses an ACOTTM mode control which provides a very fast transient response with no external compensators. The RT7291A/B operates from 5V to 23V input voltage, provides a 5V LDO and a 300kHz CLK to drive an external charge pump. OCP, UVP and OVP are included in the RT7291A/B. This IC also provides a 1.5ms internal soft-start function and an open-drain power good indicator.

Applications

Laptop Computers

Tablet PCs

Networking Systems

Servers

Personal Video Recorders

Flat Panel Television and Monitors

Distributed Power Systems

Features

5V to 23V Input Voltage Range

Up to 98% Duty for 2S Battery Application

PWM Frequency Fixed 500kHz

ACOTTM Mode Performs Fast Transient Response

Integrated MOSFETs

31mΩ of High-Side MOSFET

20mΩ of Low-Side MOSFET

Support Output MLCC Stable

Internal Soft-Start (1.5ms typ)

Built-in OVP/UVP/OCP

Power Good Indicator

Fixed 300kHz VCLK to Support Charge Pump

Individual EN for PWM and LDO

Thermal Shutdown

Simplified Application Circuit

VOUT

D1

D2

D3

 

D4

VCP

 

 

 

 

 

 

C1

C2

C3

 

C4

C5

VIN

 

 

VIN

CLK

BOOT

RB

CIN

 

 

 

 

 

RT7291A/B

CB L

 

 

 

EN

 

SW

VOUT

VLDO

 

 

LDO

 

CLDO

 

 

 

COUT

 

 

 

 

VOUT

 

 

 

 

 

 

 

RBYP

 

 

 

PGND

 

VOUT

 

VBYP

 

 

RPGOOD

 

CBYP

 

PGOOD

 

 

 

 

VCC

 

 

 

ENLDO

 

VCC

CVCC

 

 

 

AGND

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS7291A/B-02 September 2015

www.richtek.com

 

1

Functional Pin Description
Marking Information
RT7291A/B
Ordering Information
RT7291A/B

Pin Configurations

(TOP VIEW)

 

Package Type

 

AGND EN ENLDO VCC BOOT

 

 

QUF : UQFN-16L 3x3 (FC) (U-Type)

 

 

 

Lead Plating System

 

14

13

12

11

10

 

 

G : Green (Halogen Free and Pb Free)

VIN

1

 

 

 

 

 

 

Output Voltage

 

 

 

 

SW

 

 

 

 

15

 

9

 

A : 5V

PGND

2

 

SW

 

 

Note :

B : 5.1V

 

 

 

16

 

8

SW

 

 

 

SW

 

 

 

 

 

 

Richtek products are :

 

3

4

5

6

7

 

RoHS compliant and compatible with the current require-

 

VBYP

PGOOD

CLK

LDO

VOUT

 

ments of IPC/JEDEC J-STD-020.

 

 

 

 

 

 

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

UQFN-16L 3x3 (FC)

 

 

 

 

RT7291AGQUF

 

RT7291BGQUF

 

 

 

 

39= : Product Code

 

 

 

4M= : Product Code

 

 

 

 

 

 

 

39=YM

 

YMDNN : Date Code

 

4M=YM

 

YMDNN : Date Code

 

DNN

 

 

 

DNN

 

 

 

 

 

 

 

 

 

 

Pin No.

Pin Name

Pin Function

1

VIN

Power Input Connect to High-Side MOSFET Drain.

 

 

 

2

PGND

Power Ground.

 

 

 

 

 

Switch Over Source Voltage for VCC. A low pass filter should be connected to

3

VBYP

AGND, if VBYP is applied. If VBYP is not used, then connect to AGND. Do not

 

 

connect to VCC pin.

4

PGOOD

Open-Drain Power Good Indicator Output.

 

 

 

5

CLK

300kHz Clock Output to Drive the External Charge Pump.

 

 

 

6

LDO

5V Linear Regulator Output. Decouple with a minimum 4.7 F ceramic capacitor.

 

 

 

7

VOUT

Output Voltage Sense Input. An internal discharging circuit is connected to this

pin.

 

 

8, 9, 15, 16

SW

Switch Node.

 

 

 

 

 

Bootstrap Supply for High-Side Gate Driver. A capacitor is needed to drive the

10

BOOT

power switch's gate above the supply voltage. It is connected between the SW

 

 

and BOOT pins to form a floating supply across the power switch driver.

 

 

 

 

 

5V Linear Regulator Output for Internal Control Circuit. A capacitor (typical 2.2 F)

11

VCC

should be connected to AGND. VCC can only supply internal circuits. Do not

 

 

connect to external loads.

12

ENLDO

Enable Control Input for Linear Regulator. This pin is internally pulled up to high by

10 A.

 

 

13

EN

Enable Control Input. Do not leave this pin floating.

 

 

 

14

AGND

Analog Ground.

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS7291A/B-02 September 2015

2

 

RT7291A/B

Function Block Diagram

 

 

 

VCC

VBYP

 

 

 

 

 

 

 

 

 

 

 

 

VIN

 

 

Soft-Start

 

POR &

VCC

 

 

 

BSTREG

BOOT

 

Reference

 

 

 

 

 

 

 

 

VOUT

 

 

 

Switch-Over

 

 

 

 

VIN

 

 

 

 

 

 

 

 

 

 

VREF

+

 

On-Time

 

 

 

 

+

 

 

 

 

 

VFB

-

 

One shot

Gate

 

SW

 

 

 

 

Min off Time

Control

 

 

 

 

 

VCC

 

 

 

 

 

Logic

 

EN

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

 

 

 

PGND

 

120% x VREF

 

SW

+ OCP

 

 

PGOOD

 

 

VOC

-

 

 

 

 

 

 

 

 

 

 

-

OVP

 

 

 

Fault

 

 

 

+

 

-

POK

 

 

Logic

 

 

 

90% x VREF

 

 

 

 

AGND

 

 

 

+

60% x VREF

+

UVP

 

 

 

 

 

 

 

 

-

 

 

 

 

 

VOUT

 

VCC

 

 

 

 

 

VOUT

 

 

 

 

 

 

 

 

CLK

CLK

 

 

VCC

 

LDO

 

LDO

 

 

Generator

 

 

Control

 

 

 

 

 

Regulator

 

 

Switch-Over

 

 

 

 

 

VIN

 

ENLDO

LDO

 

 

Operation

Overall

The RT7291A/B is a synchronous step-down converter with advanced constant on-time control mode. Using the ACOTTM control mode can reduce the output capacitance and provide fast transient response. It can minimize the component size without additional external compensation network.

Internal VCC Regulator

The regulator provides 5V power to supply the internal control circuit. Connecting a 2.2μF ceramic capacitor for decoupling and stability is required.

Soft-Start

In order to prevent the converter output voltage from overshooting during the startup period, the soft-start function is necessary. The soft-start time is internal setting and the duration is around 1.5ms

OCP

The inductor valley current is monitored via the internal switches in cycle-by-cycle. Once the output voltage drops below UV threshold, the device enters latch mode.

Power Good

After soft-start is finished, the power good function will be activated. The PGOOD pin is an open-drain output.

CLK Generator

Provide a 300kHz clock to drive external charge pump.

VCC Switch-Over

The internal regulator output will switch over to VBYP if VBYP level is higher than 4.6V.

LDO

Built-in 5V, 100mALDO with 1% accuracy. The LDO output will switch over to VOUT once PGOOD goes high.

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS7291A/B-02 September 2015

www.richtek.com

 

3

RT7291A/B

Absolute Maximum Ratings (Note 1)

Supply Input Voltage, VIN ----------------------------------------------------------------------------------

−0.3V to 27V

Switch Voltage, SW -----------------------------------------------------------------------------------------

− 0.3V to (VIN + 0.3V)

<30ns -----------------------------------------------------------------------------------------------------------

−5V to 28V

BOOT Switch Voltage ---------------------------------------------------------------------------------------

(VSW − 0.3V) to (VSW + 6V)

EN, ENLDO Pin Voltages ----------------------------------------------------------------------------------

−0.3V to 27V

Other I/O Pin Voltages --------------------------------------------------------------------------------------

−0.3V to 6V

Power Dissipation, PD @ TA = 25°C

 

UQFN-16L 3x3 (FC) ------------------------------------------------------------------------------------------

1.4W

Package Thermal Resistance (Note 2)

 

UQFN-16L 3x3 (FC), θJA ------------------------------------------------------------------------------------

70°C/W

UQFN-16L 3x3 (FC), θJC ------------------------------------------------------------------------------------

15°C/W

Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------

260°C

Junction Temperature ----------------------------------------------------------------------------------------

150°C

Storage Temperature Range -------------------------------------------------------------------------------

−65°C to 150°C

ESD Susceptibility (Note 3)

 

HBM (Human Body Model) ---------------------------------------------------------------------------------

2kV

MM (Machine Model) ----------------------------------------------------------------------------------------

200V

Recommended Operating Conditions

(Note 4)

 

 

 

 

 

 

Supply Input Voltage, VIN

----------------------------------------------------------------------------------

 

 

 

5V to 23V

 

 

 

Junction Temperature Range -------------------------------------------------------------------------------

 

 

 

−40°C to 125°C

 

Ambient Temperature Range -------------------------------------------------------------------------------

 

 

 

−40°C to 85°C

 

Electrical Characteristics

 

 

 

 

 

 

 

 

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

 

 

 

 

 

 

 

Parameter

Symbol

Test Conditions

Min

Typ

 

Max

 

Unit

Supply Current

 

 

 

 

 

 

 

 

 

Shutdown Current

 

VEN = VENLDO = 0V

--

2.5

 

5

 

A

Quiescent Current

 

VEN = 2V, VENLDO = 2V, No Switching

--

100

 

130

 

A

Standby Current

 

VEN = 0V, VENLDO = 2V, LDO Load

--

35

 

45

 

A

 

Current = 0A

 

 

 

 

 

 

 

 

 

 

 

 

Switch On-Resistance

 

 

 

 

 

 

 

 

 

Switch On-Resistance

RDS(ON)_H

VBOOT – VSW = 5V

 

--

31

 

--

 

m

RDS(ON)_L

 

 

--

20

 

--

 

 

 

 

 

 

 

Current Limit

 

 

 

 

 

 

 

 

 

Current Limit

IOC

Valley current of low-side switch

7.6

--

 

11.4

 

A

Switching Frequency and Minimum Off Timer

 

 

 

 

 

 

 

Switching Frequency

fSW

 

 

450

500

 

550

 

kHz

Minimum Off-Time

TOFF

 

 

--

200

 

--

 

ns

Protections

 

 

 

 

 

 

 

 

 

OVP Trip Threshold

VOVP

With respect to output voltage

115

120

 

125

 

%

OVP Propagation Delay

TOVPDLY

 

 

--

5

 

--

 

s

 

 

 

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

 

www.richtek.com

DS7291A/B-02 September 2015

4

 

RT7291A/B

Parameter

Symbol

Test Conditions

Min

Typ

Max

 

Unit

 

 

 

 

 

 

 

 

 

 

UVP Trip Threshold

VUVP

With respect to output voltage

55

60

65

 

%

 

 

 

 

 

 

 

 

 

 

UVP Propagation Delay

TUVPDLY

 

 

--

5

--

 

s

 

 

 

 

 

 

 

 

 

 

Reference and Soft-Start

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Output Voltage Valley

VOUT

RT7291A

 

4.95

5

5.05

 

V

 

 

 

 

 

 

RT7291B

 

5.049

5.1

5.151

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Soft-Start Time

 

TSS

From EN high to PGOOD high

1

1.5

2

 

ms

 

 

 

 

 

 

 

 

 

 

Enable and UVLO

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EN Input High Voltage

VENH

RT7291A

 

1.25

1.35

1.45

 

V

 

 

 

 

 

 

RT7291B

 

1.3

1.4

1.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EN Hysteresis

 

VENHYS

 

 

--

200

--

 

mV

 

 

 

 

 

 

 

 

 

 

 

EN Input Current

IEN

VEN = 2V

 

--

1

--

 

A

 

 

 

 

 

 

VEN = 0V

 

--

0

--

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCC UVLO Rising

VCCUVLO

 

 

--

4.2

--

 

V

 

 

 

 

 

 

 

 

 

 

VCC UVLO Hysteresis

VCCHYS

 

 

--

400

--

 

mV

 

 

 

 

 

 

 

 

 

 

 

CLK Output

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CLK Output

 

High-Level

VCLKH

IVCLK = 10mA

RT7291A

--

--

5.05

 

 

 

 

 

 

 

 

 

 

RT7291B

--

--

5.151

 

V

Voltage

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Low-Level

VCLKL

IVCLK = 10mA

 

0

0.1

0.2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CLK Frequency

 

fCLK

 

 

--

300

--

 

kHz

 

 

 

 

 

 

 

 

 

 

 

LDO Regulator

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LDO Regulator

 

VLDO

RT7291A

 

4.95

5

5.05

 

V

 

 

 

 

 

 

 

 

RT7291B

 

5.049

5.1

5.151

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EN = GND,

 

--

1

--

 

 

 

 

 

 

LDO Load Current = 5mA

 

 

LDO Load Regulation

 

 

 

 

 

%

 

 

 

 

 

 

 

 

EN = GND,

 

--

5

--

 

 

 

 

 

 

 

 

 

 

 

 

LDO Load Current = 100mA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Switch On-Resistance

RSW

 

 

--

3

5

 

 

 

 

 

 

 

 

 

 

 

 

VCC Regulator

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCC Regulator

 

VVCC

RT7291A

 

4.805

5

5.295

 

V

 

 

 

 

 

 

 

 

RT7291B

 

4.905

5.1

5.395

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCC Switch Over Threshold to

 

VBYP Rising

RT7291A

4.45

4.6

4.75

 

V

 

 

 

 

 

 

VBYP

 

 

Edge

RT7291B

4.542

4.692

4.842

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCC Switch Over Hysteresis

 

VBYP Falling Edge

--

200

--

 

mV

 

 

 

 

 

 

 

 

 

Switch Over On-Resistance

 

 

 

--

3

5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

 

DS7291A/B-02 September 2015

www.richtek.com

 

5

RT7291A/B

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

Power Good Indicator

 

 

 

 

 

 

PGOOD Threshold From Lower

 

VOUT Rising

85

90

95

%

PGOOD Low Hysteresis

 

VOUT Falling

--

10

--

%

 

 

 

 

 

 

 

PGOOD Low to High Delay

TPGDLY

 

--

0.5

--

ms

 

 

 

 

 

 

 

PGOOD Sink Current Capability

VPGSINK

Sink 4mA

--

--

0.4

V

 

 

 

 

 

 

 

PGOOD Leakage Current

IPGLEAK

VPGOOD = 5V

--

--

100

nA

 

 

 

 

 

 

 

Thermal Shutdown

 

 

 

 

 

 

 

 

 

 

 

 

 

Thermal Shutdown Threshold

TSD

 

135

150

--

°C

 

 

 

 

 

 

 

Thermal Shutdown Hysteresis

 

 

--

25

--

°C

 

 

 

 

 

 

 

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

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

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS7291A/B-02 September 2015

6

 

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