Richtek RT8237CZQW, RT8237DZQW Schematic [ru]

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®

RT8237C/D

High Efficiency Single Synchronous Buck PWM Controller

General Description

The RT8237C/D 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 RT8237C/Dachieves 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 pre-set frequency selections minimize design effort required for new designs. The RT8237C/D is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 0.7V. The RT8237C is available in a WDFN-10L 3x3 package, The RT8237D is available in a WQFN-12L 2x2 package.

Features

Wide Input Voltage Range : 4.5V to 26V

Output Voltage Range : 0.7V to 3.3V

Built-in 0.5% 0.7V Reference Voltage

Quick Load-Step Response within 100ns

4700ppm/°C Programmable Current Limit by Low

Side RDS(ON) Sensing

4 Selectable Frequency Setting

Soft-Start Control

Drives Large Synchronous-Rectifier FETs

Integrated Boot Switch

Built-in OVP/OCP/UVP

Thermal Shutdown

Power Good Indicator

RoHS Compliant and Halogen Free

Applications

Notebook Computers

CPU Core Supply

Chipset/RAM Supply as Low as 0.7V

Generic DC/DC Power Regulator

Pin Configurations

(TOP VIEW)

Ordering Information

PGOOD 1

 

10

BOOT

CS 2

GND

9

UGATE

RT8237

(2)

EN 3

8

PHASE

FB 4

7

VCC

 

 

 

 

Pin 1 Orientation

RF 5

11

6

LGATE

 

(2) : Quadrant 2, Follow EIA-481-D

 

WDFN-10L 3x3

 

 

Package Type

 

 

 

 

RT8237C

 

 

 

QW : WDFN-10L 3x3 (W-Type)

 

 

 

 

 

GND

NC

RF

 

 

 

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

 

 

 

 

 

 

 

 

 

 

 

Lead Plating System

 

12

11

10

 

 

 

Z : ECO (Ecological Element with

LGATE

1

 

 

9

FB

 

Halogen Free and Pb free)

 

 

 

VCC

2

GND

8

EN

 

C : WDFN-10L 3x3

 

PHASE

3

 

13

7

CS

Note :

D : WQFN-12L 2x2

 

4

5

6

 

 

 

 

 

 

 

 

UGATE

BOOT

PGOOD

 

 

RoHS compliant and compatible with the current require-

 

 

 

Richtek products are :

 

 

 

 

 

 

ments of IPC/JEDEC J-STD-020.

 

WQFN-12L 2x2

 

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

RT8237D

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8237C/D-06 February 2014

www.richtek.com

 

1

RT8237C/D

Marking Information

RT8237CZQW

 

RT8237DZQW

 

 

 

 

Z3 : Product Code

 

 

 

 

 

72 : Product Code

 

 

 

 

 

 

 

 

 

Z3 YM

 

YMDNN : Date Code

 

72W

 

W : Date Code

 

DNN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Typical Application Circuit

 

R1

 

VCC

0

 

C1

 

 

R5

 

1µF

 

100k

 

16V

 

 

Chip Enable

 

 

RRF

ROC_SET

 

470k

 

 

30k

 

* : Optional

 

 

 

CBOOT

VIN

 

 

 

 

 

 

 

 

 

 

 

 

RT8237C/D

RBOOT

0.1µF

 

 

 

 

 

50V

 

 

 

 

 

VCC

BOOT

0

C2

 

 

 

 

 

 

 

 

 

 

 

 

 

10µF x 3

 

 

 

 

 

 

RUGATE

50V

 

 

 

 

 

UGATE

 

 

 

 

 

PGOOD

0

 

 

 

 

 

VOUT

 

 

LOUT

 

 

 

 

 

 

 

 

 

 

1.05V

EN

 

 

 

0.45µH

 

 

 

 

PHASE

RLGATE

 

 

 

 

C6

 

 

LGATE

 

R2*

 

 

COUT

 

 

 

 

 

10µF x 2

RF

0

 

 

 

330µF x 2

 

 

 

 

 

16V

CS

 

 

 

C3*

RFB1

R3*

 

16V

 

 

 

 

 

5.1k

C4*

 

 

 

 

 

 

 

 

C5*

 

GND

FB

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RFB2

 

 

 

 

 

 

 

 

10k

 

 

 

Functional Pin Description

Pin No.

Pin Name

 

Pin Function

 

RT8237C

RT8237D

 

 

 

 

 

 

1

6

PGOOD

Open Drain

Power Good Indicator. High impedance indicates

 

power is good.

 

 

 

 

 

 

 

 

Current Limit Threshold Setting Input. Connect a setting resistor to

 

2

7

CS

GND and the current limit threshold is equal to 1/8 of the voltage

 

 

 

 

at this pin.

 

 

3

8

EN

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

 

4

9

FB

VOUT Feedback Input. Connect FB to a resistor voltage divider

 

from VOUT to GND to adjust the output from 0.7V to 3.3V

 

 

 

 

 

 

 

 

Switching Frequency Selection. Connect a resistance to select

 

 

 

 

switching frequency as shown in Electrical Characteristics.

 

5

10

RF

The switching frequency is detected and latched after startup. This

 

pin also controls Diode emulation mode or forced CCM selection.

 

 

 

 

Pull down to GND with resistor : Diode Emulation Mode.

 

 

 

 

Connect to PGOOD with resistor : forced CCM after PGOOD

 

 

 

 

becomes high.

 

6

1

LGATE

Gate Drive Output for Low Side External MOSFET.

 

 

 

 

Control Voltage Input. This pin provides the power for the buck

 

7

2

VCC

controller, the low side driver and the bootstrap circuit for high side

 

 

 

 

driver. Bypass to GND with a 1 F ceramic capacitor.

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8237C/D-06 February 2014

2

 

Richtek RT8237CZQW, RT8237DZQW Schematic

 

 

 

RT8237C/D

 

 

 

 

 

Pin No.

Pin Name

Pin Function

 

RT8237C

RT8237D

 

 

 

 

 

 

 

External Inductor Connection Pin for PWM Converter. It behaves

 

8

3

PHASE

as the current sense comparator input for low side MOSFET

 

 

 

 

RDS(ON) sensing and reference voltage for on time generation.

 

9

4

UGATE

Gate Drive Output for High Side External MOSFET.

 

10

5

BOOT

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

 

the floating node (PHASE) pin.

 

 

 

 

 

---

11

NC

No Internal Connection.

 

11

12, 13

GND

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

 

(Exposed Pad)

(Exposed Pad)

connected to GND for maximum power dissipation.

 

Function Block Diagram

 

 

 

TRIG

 

 

 

 

 

 

VCC

 

RF

 

 

 

On-time

 

 

 

 

 

 

 

 

 

 

Compute

 

 

 

 

 

 

 

BOOT

 

PHASE

 

 

 

 

 

 

 

 

 

 

 

1-SHOT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R

 

 

 

 

 

 

 

 

 

-COMP

 

 

 

 

 

 

 

 

 

 

 

S

Q

PWM

 

UGATE

 

 

 

 

 

+

 

 

DRV

 

 

 

 

 

 

 

 

 

 

 

 

VREF

 

 

 

Min. tOFF

 

 

 

PHASE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+

OV

Latch

Q

TRIG

 

 

 

 

 

 

125%

S1

Q

 

1-SHOT

 

 

 

 

 

 

VREF

-

 

Latch

 

 

 

 

DRV

LGATE

FB

 

 

+

UV

 

 

 

 

 

70%

S1

Q

 

 

 

 

 

GND

 

 

-

 

 

 

 

 

 

 

 

VREF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DEM/FCCM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

125% VREF

-

 

 

 

 

 

PGOOD

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCC

POR

SS

 

 

 

-

 

 

 

 

 

 

 

 

Timer

90% VREF

+

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EN

 

 

 

 

Thermal

 

-

 

 

 

 

 

 

 

 

 

Shutdown

 

+

 

 

 

 

 

 

 

 

 

 

 

 

X(1/8)

 

 

 

 

 

10µA

 

 

 

 

 

 

 

+

 

 

 

 

 

 

 

 

 

 

 

-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

X(-1/8)

 

 

CS

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8237C/D-06 February 2014

www.richtek.com

 

3

RT8237C/D

Absolute Maximum Ratings

(Note 1)

 

 

 

 

 

 

VCC, FB, PGOOD, EN, CS, RF to GND

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

 

 

 

 

−0.3V to 6V

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

 

 

 

 

 

 

 

−0.3V to 6V

PHASE to GND

 

 

 

 

 

 

 

 

 

 

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

 

 

 

 

 

 

 

−0.3V to 32V

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

 

 

 

 

 

 

 

−8V to 38V

UGATE to PHASE --------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

−0.3V to 6V

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

 

 

 

 

 

 

 

−0.3V to 6V

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

 

 

 

 

 

 

 

−5V to 7.5V

LGATE to GND -------------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

−0.3V to 6V

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

 

 

 

 

 

 

 

−0.3V to 6V

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

 

 

 

 

 

 

 

−2.5V to 7.5V

Power Dissipation, PD @ TA = 25°C

 

 

 

 

 

 

 

 

WDFN-10L 3x3 -------------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

0.952W

 

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

 

 

 

 

 

 

 

0.606W

 

Package Thermal Resistance (Note 2)

 

 

 

 

 

 

 

 

WDFN-10L 3x3, θJA -------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

105°C/W

 

WDFN-10L 3x3, θJC -------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

 

8.2°C/W

 

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

 

 

 

 

 

 

 

165°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)

 

 

 

 

 

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

 

 

 

 

 

 

 

4.5V to 26V

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

 

 

 

 

 

 

 

4.5V to 5.5V

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

 

 

 

 

 

 

 

−40°C to 125°C

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

 

 

 

 

 

 

 

−40°C to 85°C

Electrical Characteristics

 

 

 

 

 

 

 

 

(VCC = 5V, TA = 25°C, unless otherwise specified)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Parameter

 

Symbol

 

 

Test Conditions

Min

Typ

Max

 

Unit

Input Power Supply

 

 

 

 

 

 

 

 

 

 

VCC Quiescent Supply

 

IQ

 

FB

forced above the

regulation

--

500

1250

 

A

Current

 

 

point, VEN = 5V,

 

 

 

 

 

 

 

 

 

 

 

VCC Shutdown Current

 

ISHDN

 

VCC current, VEN = 0V

 

--

--

1

 

A

CS Shutdown Current

 

 

 

CS pull to GND

 

--

--

1

 

A

 

 

 

 

 

 

 

 

 

 

 

FB Error Comparator

 

VREF

 

DEM

 

0.7005

0.704

0.7075

 

V

Threshold

 

 

DEM, TA = 40 to 85 C

(Note 5)

0.697

0.704

0.711

 

 

 

 

 

 

FB Input Bias Current

 

 

 

VFB = 0.735V

 

1

0.01

1

 

A

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8237C/D-06 February 2014

4

 

RT8237C/D

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

 

VOUT Voltage Range

 

 

 

0.7

--

3.3

V

 

 

 

 

RRF = 470k

(Note 6)

--

290

--

 

 

Switching Frequency

fSW

RRF = 200k

(Note 6)

--

340

--

kHz

 

RRF = 100k

(Note 6)

--

380

--

 

 

 

 

 

 

 

 

 

RRF = 39k

(Note 6)

--

430

--

 

 

Minimum Off-Time

 

 

 

 

250

400

550

ns

 

Current Sensing

 

 

 

 

 

 

 

 

 

CS Source Current

 

ICS

 

 

9

10

11

A

 

CS Source Current TC

 

 

 

--

4700

--

ppm/ C

 

Zero Crossing Threshold

 

DEM

 

10

--

5

mV

 

 

 

 

 

 

 

 

 

 

 

 

 

GND PHASE, VCS = 2.4V

280

300

320

 

 

Current Limit Threshold

VLIMIT

GND PHASE, VCS = 1.6V

185

200

215

mV

 

 

 

 

GND PHASE, VCS = 0.4V

40

50

60

 

 

Negative Current Limit

 

PHASE GND, VCS = 2.4V

--

300

--

 

 

 

 

 

--

200

--

mV

 

Threshold

 

 

PHASE GND, VCS = 1.6V

 

 

 

 

PHASE GND, VCS = 0.4V

--

50

--

 

 

 

 

 

 

 

Protection Function

 

 

 

 

 

 

 

 

Output UV Threshold

 

With respect to error

65

70

75

%

 

 

comparator threshold

 

 

 

 

 

 

 

 

 

OVP Threshold

 

 

With respect to error

120

125

130

%

 

 

 

comparator threshold

 

 

 

 

 

 

 

 

 

OV Fault Delay

 

 

FB forced above OV threshold

--

5

--

s

 

VCC Under Voltage Lockout

 

Falling edge,

 

 

 

 

 

 

UVLO

hysteresis = 100mV, PWM

3.7

3.9

4.1

V

 

Threshold

 

 

 

 

disabled below this level

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT Soft-Start

 

 

From EN = high to VOUT = 95%

--

1300

--

s

 

UV Blank Time

 

 

From EN signal going high

--

3

--

ms

 

Thermal Shutdown

 

TSD

 

 

--

150

--

C

 

Driver On Resistance

 

 

 

 

 

 

 

 

UGATE Drive Source

RUGATEsr

BOOT PHASE forced to 5V

--

1.8

3.6

 

 

UGATE Drive Sink

 

RUGATEsk

BOOT PHASE forced to 5V

--

1.2

2.4

 

 

LGATE Drive Source

RLGATEsr

LGATE, High State

--

1.8

3.6

 

 

LGATE Drive Sink

 

RLGATEsk

LGATE, Low State

--

0.8

1.6

 

 

Dead Time

 

 

LGATE Rising (VPHASE = 1.5V)

--

30

--

ns

 

 

 

UGATE Rising

 

--

30

--

 

 

 

 

 

 

 

Internal Boost Charging Switch

 

VCC to BOOT, 10mA

--

--

80

 

 

On Resistance

 

 

 

 

 

 

 

 

 

 

 

 

EN Threshold

 

 

 

 

 

 

 

 

 

EN Input

Logic-High

VIH

 

 

1.8

--

--

V

 

Threshold Voltage

Logic-Low

VIL

 

 

--

--

0.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8237C/D-06 February 2014

www.richtek.com

 

5

RT8237C/D

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

Mode Decision

 

 

 

 

 

 

VRF Threshold for DEM

 

 

--

--

0.5

V

VRF Threshold for FCCM

 

 

1.8

--

--

V

PGOOD

 

 

 

 

 

 

Trip Threshold (falling,

 

Measured at FB, with respect to

87

90

93

%

leaving PGOOD)

 

reference, Hysteresis = 3%

 

 

 

 

 

Trip Threshold (rising,

 

Measured at FB, with respect to

120

125

130

%

leaving PGOOD)

 

reference, Hysteresis = 3%

 

 

 

 

 

Fault Propagation Delay

 

Falling Edge, FB forced below

--

2.5

--

s

 

PGOOD trip threshold

 

 

 

 

 

 

Output Low Voltage

 

ISINK = 1mA

--

--

0.4

V

Leakage Current

 

High State, forced to 5V

--

--

1

A

 

 

 

 

 

 

 

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 low effective thermal conductivity single-layer test board per JEDEC 51-3. 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. Guaranteed by design. Not production tested.

Note 6. Not production tested. Test condition is VIN = 8V, VOUT = 1.1V, IOUT = 10A using application circuit.

Copyright ©2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8237C/D-06 February 2014

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