Richtek RT8228AGQW, RT8228AZQW Schematic [ru]

Loading...

®

RT8228A

Single Synchronous Buck PWM Controller

General Description

The RT8228A PWM controller provides high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high voltage batteries to generate low voltage CPU core, I/O, and chipset RAM supplies in notebook computers.

The constant on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns “instant-on” response to load transients while maintaining a relatively constant switching frequency.

The RT8228A achieves high efficiency at a reduced cost by eliminating the current sense resistor found in traditional current mode PWMs. Efficiency is further enhanced by its ability to drive very large synchronous rectifier MOSFETs and enter diode emulation mode at light load condition. The buck conversion allows this device to directly step down high voltage batteries at the highest possible efficiency. The Audio Skipping Mode (ASM) setting maintains the switching frequency above 25kHz, which eliminates noise in audio applications. The RT8228A is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 0.5V. The RT8228A is available in a WQFN-12L 2x2 package.

Ordering Information

RT8228A

Package Type

QW : WQFN-12L 2x2 (W-Type)

Lead Plating System

G : Green (Halogen Free and Pb Free) Z : ECO (Ecological Element with

Halogen Free and Pb free)

Note :

Richtek products are :

`RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.

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

Features

zBuilt in 1% 0.5V Reference Voltage

zAdjustable 0.5V to 3.3V Output Range

zQuick Load Step Response within 100ns

z4700ppm/°C Programmable Current Limit by Low

Side RDS(ON) Sensing

z4.5V to 26V Battery Input Range

zResistor Programmable Frequency

zInternal Ramp Current Limit Soft-Start Control

zDrives Large Synchronous Rectifier FETs

zIntegrated Boost Switch

zOver/Under Voltage Protection

zThermal Shutdown

zPower Good Indicator

zRoHS Compliant and Halogen Free

Applications

zNotebook Computers

zCPU Core Supply

zChipset/RAM Supply as Low as 0.5V

zGeneric DC/DC Power Regulator

Pin Configurations

(TOP VIEW)

 

GND

TON

CS

 

 

 

12

11

10

 

 

LGATE

1

 

 

9

PGOOD

PHASE

2

GND

 

8

EN

UGATE

3

13

7

MODE

 

 

 

4

5

6

 

 

 

BOOT

VCC

FB

 

 

 

WQFN-12L 2x2

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8228A-06 January 2014

www.richtek.com

 

1

RT8228A

Marking Information

RT8228AGQW

CQ : Product Code

RT8228AZQW

CQ : Product Code

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CQW

 

W : Date Code

 

CQW

 

W : Date Code

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Typical Application Circuit

VIN

 

 

 

 

 

 

4.5V to 26V

 

 

 

 

 

 

 

R

 

 

 

 

 

 

 

 

 

 

TON

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C4

 

 

 

 

 

 

RT8228A

 

R4

 

10µF

 

 

 

 

11

 

4

 

 

 

 

 

 

TON

BOOT

0

 

 

 

 

 

 

 

 

 

C3

 

 

 

 

VDDP

5

VCC

 

 

R5

 

 

 

V

 

 

3

0

0.1µF

 

 

 

OUT

 

 

 

UGATE

 

 

 

1V

 

C2

 

 

Q1

 

 

 

 

 

 

 

L1

* : Optional

R2

4.7µF

 

PHASE

2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

100k

 

 

 

 

 

 

 

 

 

 

 

LGATE

1

 

Q2

R7*

C5*

C6*

C1

 

 

 

 

 

 

 

 

 

220µF

 

 

 

 

 

 

 

 

R8

 

PGOOD

9

PGOOD

 

 

 

C7*

10k

 

 

10

 

 

 

 

 

 

 

 

CS

FB

6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R6

 

 

7

 

To 5V : DEM

 

R9

 

 

 

 

 

MODE

 

To 2.5V : ASM

 

10k

 

 

 

 

 

 

 

 

 

 

Chip Enable

8

EN

 

 

 

To GND : FCCM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

12,

13 (Exposed Pad)

 

 

 

 

 

 

 

GND

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

RT8228A-06 January 2014

2

Richtek RT8228AGQW, RT8228AZQW Schematic

 

 

 

RT8228A

Functional Pin Description

 

Pin No.

Pin Name

Pin Function

 

1

LGATE

Gate Drive Output for Low Side External MOSFET.

 

 

 

External Inductor Connection Pin for PWM Converter. It behaves as the current

 

2

PHASE

sense comparator input for Low Side MOSFET RDS(ON) sensing and reference

 

 

 

voltage for on time generation.

 

3

UGATE

Gate Drive Output for High Side External MOSFET.

 

 

 

 

 

4

BOOT

Supply Input for High Side Driver. Connect through a capacitor to the floating

 

node (PHASE) pin.

 

 

 

 

 

 

Control Voltage Input. Provides the power for the buck controller, the low side

 

5

VCC

driver and the bootstrap circuit for high side driver. Bypass to GND with a 4.7μF

 

 

 

ceramic capacitor.

 

6

FB

VOUT Feedback Input. Connect FB to a resistive voltage divider from VOUT to

 

GND to adjust the output from 0.5V to 3.3V

 

 

 

 

 

 

Pull Down to GND for Forced CCM Mode.

 

7

MODE

Pull Up to 2.5V for Audio Skipping Mode (ASM).

 

 

 

Pull Up to 5V for Diode Emulation Mode (DEM).

 

8

EN

PWM Chip Enable. Pull low to GND to disable the PWM.

 

9

PGOOD

Open Drain Power Good Indicator. High impedance indicates power is good.

 

 

 

 

 

10

CS

Current Limit Threshold Setting Input. Connect a setting resistor to GND and the

 

current limit threshold is equal to 1/10 of the voltage at this pin.

 

 

 

 

11

TON

On-time Setting. Connect a resistor between this pin and VIN.

 

12,

GND

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

 

13 (Exposed Pad)

GND for maximum power dissipation.

Function Block Diagram

 

 

 

TRIG

 

 

 

 

 

 

 

 

TON

 

 

 

On-time

 

 

 

 

 

 

 

 

 

 

Compute

 

 

 

 

 

 

 

BOOT

 

PHASE

 

 

 

 

 

 

 

 

 

 

 

1-SHOT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R

 

 

 

 

 

 

 

 

 

 

-COMP

 

 

 

 

 

 

 

PSR

 

 

 

 

S

Q

PWM

 

UGATE

 

 

 

 

 

 

+

 

DRV

 

 

 

 

 

 

 

 

 

 

 

 

0.5V VREF

 

 

Min. TOFF

 

 

 

PHASE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+

OV

Latch

Q

TRIG

 

 

VCC

 

 

125% VREF

S1

Q

 

1-SHOT

 

 

 

 

 

-

 

 

 

 

 

 

 

 

Latch

 

 

 

 

DRV

LGATE

FB

 

 

-

UV

 

 

 

 

70% VREF

S1

Q

 

 

 

 

 

 

 

 

 

 

 

 

GND

 

+

 

 

 

DEM/FCCM/ASM

 

 

 

 

 

 

 

 

 

 

 

 

 

MODE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

125% VREF

-

 

 

 

 

 

PGOOD

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCC

POR

SS

 

 

 

-

 

 

 

 

 

 

 

 

Timer

90% VREF

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EN

 

 

 

 

Thermal

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

10µA

 

 

 

Shutdown

 

 

-

X(-1/10)

 

 

CS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

 

is a registered trademark of Richtek Technology Corporation.

RT8228A-06 January 2014

www.richtek.com

3

RT8228A

Absolute Maximum Ratings (Note 1)

z VCC to GND ---------------------------------------------------------------------------------------------------------

–0.3V to 6V

z FB, PGOOD, EN, CS, MODE to GND ------------------------------------------------------------------------

–0.3V to (VCC + 0.3V)

z TONtoGND ----------------------------------------------------------------------------------------------------------

–0.3V to 32V

z BOOT to PHASE ---------------------------------------------------------------------------------------------------

–0.3V to 6.5V

z PHASE to GND

 

DC ----------------------------------------------------------------------------------------------------------------------

−0.3V to 32V

< 20ns ----------------------------------------------------------------------------------------------------------------

−8V to 38V

z UGATE to PHASE

 

DC ----------------------------------------------------------------------------------------------------------------------

−0.3V to (VCC + 0.3V)

< 20ns ----------------------------------------------------------------------------------------------------------------

−5V to 7.5V

z LGATE to GND

 

DC ----------------------------------------------------------------------------------------------------------------------

−0.3V to (VCC + 0.3V)

< 20ns ----------------------------------------------------------------------------------------------------------------

−2.5V to 7.5V

z Power Dissipation, PD @ TA = 25°C

 

WQFN-12L 2x2 -----------------------------------------------------------------------------------------------------

0.606W

z Package Thermal Resistance (Note 2)

 

WQFN-12L 2x2, θJA ------------------------------------------------------------------------------------------------

165°C/W

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

260°C

z Junction Temperature ----------------------------------------------------------------------------------------------

150°C

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

−65°C to 150°C

z ESD Susceptibility (Note 3)

 

HBM (Human Body Mode) ---------------------------------------------------------------------------------------

2kV

MM (Machine Mode) -----------------------------------------------------------------------------------------------

200V

Recommended Operating Conditions

(Note 4)

z Input Voltage, VIN ---------------------------------------------------------------------------------------------------

4.5V to 26V

z Control Voltage, VCC -----------------------------------------------------------------------------------------------

4.5V to 5.5V

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

−40°C to 125°C

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

−40°C to 85°C

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

RT8228A-06 January 2014

4

 

RT8228A

Electrical Characteristics

(VCC = 5V, VIN = 15V, VEN = 5V, VMODE = 5V, RTON = 500kΩ, TA = 25°C, unless otherwise specified)

 

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

 

PWM Controller

 

 

 

 

 

 

 

 

VCC Quiescent Supply Current

IQ

FB forced above the regulation

--

0.5

1.25

mA

 

point, VEN = 5V

 

 

 

 

 

 

 

 

 

 

VCC Shutdown Current

ISHDN

VCC Current, VEN = 0V

--

--

1

μ

 

 

 

 

A

 

TON Operating Current

 

RTON = 500k

 

--

30

--

μ

 

 

 

 

 

 

 

A

 

TON Shutdown Current

 

RTON = 500k

 

--

--

1

μA

 

CS Shutdown Current

 

CS pull to GND

 

--

--

1

μA

 

FB Error Comparator

 

VCC = 4.5V to 5.5V, DEM

495

500

505

mV

 

Threshold Voltage

 

 

 

 

 

 

 

 

 

 

FB Input Bias Current

 

VFB = 0.5V

 

−1

0.1

1

μA

 

Output Voltage Range

 

 

 

0.5

--

3.3

V

 

On-Time

 

VIN =15V, VPHASE = 1.25V,

267

334

401

ns

 

 

VMODE = 0V

 

 

 

 

 

 

 

 

 

 

Minimum Off-Time

 

VMODE = 0V, FB = 0.45V

250

400

550

ns

 

Current Sensing Threshold

 

 

 

 

 

 

 

 

CS Source Current

 

VCS = 0.5V to 2V

 

9

10

11

μA

 

CS Source Current TC

 

On the basis of 25°C

--

4700

--

ppm/°C

 

Zero Crossing Threshold

 

VMODE > 1.8V, PHASE − GND

−10

--

5

mV

 

ASM Min Frequency

 

VMODE = 2.5V

 

--

25

--

kHz

 

Protection Function

 

 

 

 

 

 

 

 

Current Limit Threshold

 

GND − PHASE, VCS = 1V

85

100

115

mV

 

UV Threshold

 

UVP Detect, FB Falling Edge

60

70

80

%

 

 

 

 

 

 

 

 

 

OVP Threshold

 

OVP Detect, FB Rising Edge

120

125

130

%

 

OV Fault Delay

 

FB forced above OV threshold

--

5

--

μs

 

VCC Power On Reset (POR)

 

Rising Edge

 

3.7

3.9

4.2

V

 

Threshold

 

 

 

 

 

 

 

 

POR Threshold Hysteresis

 

 

 

--

100

--

mV

 

Current Limit Ramp at

 

Enable to current limit threshold =

--

900

--

μs

 

Soft-Start

 

50mV

 

 

 

 

 

 

 

 

 

UV Blank Time

 

From EN signal going high

--

4.5

--

ms

 

Thermal Shutdown

TSD

 

 

--

150

--

°C

 

Thermal Shutdown Hysteresis

TSD

 

 

--

10

--

°C

 

Driver On-Resistance

 

 

 

 

 

 

 

 

UGATE Driver Source

RUGATEsr

BOOT − PHASE forced to 5V,

--

2.5

5

Ω

 

UGATE High State

 

 

UGATE Driver Sink

RUGATEsk

BOOT − PHASE forced to 5V,

--

1.5

3

Ω

 

UGATE Low State

 

 

LGATE Driver Source

RLGATEsr

LGATE High State

 

--

2.5

5

Ω

 

LGATE Driver Sink

RLGATEsk

LGATE Low State

 

--

0.8

1.5

Ω

 

Dead Time

 

LGATE Rising (Phase = 1.5V)

--

30

--

ns

 

 

UGATE Rising

 

--

30

--

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

RT8228A-06 January 2014

 

 

 

 

 

www.richtek.com

 

 

 

 

 

 

 

 

5

+ 11 hidden pages