Richtek RT8237CZQW, RT8237DZQW Schematic [ru]

RT8237C/D

High Efficiency Single Synchronous Buck PWM Controller

General Description

The RT8237C/D PWM controller provides high efficiency , excellent transient response, a nd high DC output a ccuracy 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 ha ndles wide input/output voltage ratios with ea se and provides 100ns “instant-on” response to load transients while maintaining a relatively constant switching frequency .

The RT8237C/D 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 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 a s low a s 0.7V . The RT8237C is available in a W DF N-10L 3x3 package, The R T8237D 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/



Side R



 4 Selectable Frequency Setting



 Soft-Start Control



 Drives Large Synchronous-Rectifier FET s



 Integrated Boot Switch



 Built-in OVP/OCP/UVP



 Thermal Shutdown



 Power Good Indicator



 RoHS Compliant and Halogen Free



°°

°C Programmable Current Limit by Low

°°

Sensing

DS(ON)

Applications

 Notebook Computers  CPU Core Supply  Chipset/RAM Supply a s Low as 0.7V  Generic DC/DC Power Regulator

Pin Configurations

(TOP VIEW)

GND

9 8 7 6

BOOT UGATE PHASE VCC LGATE

Ordering Information

RT8237

(2)

Pin 1 Orientation (2) : Quadrant 2, Follow EIA-481-D

Package Type

PGOOD

CS EN

1 2 3 4 5

WDFN-10L 3x3

RT8237C

QW : WDFN-10L 3x3 (W-Type) QW : WQFN-12L 2x2 (W-Type)

Lead Plating System Z : ECO (Ecological Element with Halogen Free and Pb free)

C : WDFN-10L 3x3

LGATE FB

VCC

PHASE

D : WQFN-12L 2x2

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.

DS8237C/D-06 February 2014 www.richtek.com

GNDNCRF

12 1011

GND

2 3

BOOT

UGATE

654

PGOOD

WQFN-12L 2x2

RT8237D

9 8

RT8237C/D

Marking Information

RT8237CZQW

Z3 : Product Code

Z3 YM

DNN

Typical Application Circuit

Chip Enable

YMDNN : Date Code

1µF

100k

16V

470k

OC_SET

30k

RT8237DZQW

72 : Product Code

72W

BOOT

LGATE

UGATE

0.1µF 50V

BOOT

W : Date Code

C2 10µF x 3 50V

OUT

0.45µH

R2*

C3*

FB1

5.1k

FB2

10k

R3*

C4*

OUT

1.05V

C6 10µF x 2 16V

C5*

OUT

330µF x 2 16V

Functional Pin Description

Pin No.

RT8237C RT8237D

1 6 PGOOD

2 7 CS

3 8 EN PWM Enable. Pull low to GND to disable the PWM. 4 9 FB

5 10 RF

6 1 LGATE Gate Drive Output for Low S ide External MOSFET.

7 2 VCC

Pin Name Pi n Func t i o n

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

Curren t Li mit Thr eshold Setting I nput . Connect a setti ng r esi stor to GND and the current limit threshold is equal to 1/8 of the volt age at this pin.

Feedback Input. Connect FB to a resistor voltage divider

OUT

fro m V

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

OUT

Switching Frequency Selection. Connect a resistance to select switching frequency as shown in Electrical Charac t er istics. The swi t c hin g frequency is det ect ed and latched af ter start up. This pin also cont rols Diode emulat ion mode or forced C CM selection. Pull down to GND with resistor : Diode Emulation Mode. Connect to PGOOD with resistor : forced CCM after PGOOD becomes hi gh.

Contr ol Voltage Input. This pin provides the power for the buck contr oller, the low si de dr iv er an d th e bootstrap ci rcuit for high side dri v er. Byp ass to GND wi th a 1F ceramic capa citor.

DS8237C/D-06 February 2014www.richtek.com

RT8237C/D

Pin No.

Pin Name Pi n Func t i o n

RT8237C RT8237D

8 3 PHASE

9 4 UGATE Gate Drive Output for High Side Exter nal MOSFET.

10 5 BOOT

--- 11 NC No Internal Connection. 11

(Expo sed Pad)

12, 13

(Exp osed Pad)

GND

Function Block Diagram

TRIG

PHASE

On-time

Compute

1-SHOT

External Inductor C onnection Pin for PWM Converter. It behaves as the current sense comparator input for low side MOSFET R

sensing and r eference voltage for on time generation.

DS(ON)

Supply Input for High Si de Driver. Connect through a capacitor to the float ing node (PHASE) pin.

Ground. The exposed pad must be soldered to a large PCB and conn ect ed to GND for maxim um power dissipation.

VCC

COMP

PWM

DRV

BOOT

UGATE

VCC

POR

10µA

125%

REF

70%

REF

Timer

REF

125% V

90% V

Latch

S1 Q

Latch

S1 Q

REF

Thermal

Shutdown

Min. t

OFF

QTRIG

1-SHOT

DEM/FCCM

X(1/8)

X(-1/8)

DRV

PHASE

LGATE GND

PGOOD

DS8237C/D-06 February 2014 www.richtek.com

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

 UGA TE to PHASE -------------------------------------------------------------------------------------------------------- −0.3V to 6V

DC----------------------------------------------------------------------------------------------------------------------------- −0.3V to 6V <20ns ------------------------------------------------------------------------------------------------------------------------ −5V to 7.5V

 LGA TE to GN D ------------------------------------------------------------------------------------------------------------- −0.3V to 6V

 Power Dissipation, P

W D FN-10L 3x3------------------------------------------------------------------------------------------------------------- 0.952W WQFN-12L 2x2 ------------------------------------------------------------------------------------------------------------ 0.606W

 Package Thermal Re sistance (Note 2)

W DFN-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 T emperature----------------------------------------------------------------------------------------------------- 150°C  Storage T emperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C  ESD Susceptibility (Note 3)

HBM (Human Body Model)---------------------------------------------------------------------------------------------- 2kV MM (Machine Model) ----------------------------------------------------------------------------------------------------- 200V

@ TA = 25°C

Recommended Operating Conditions (Note 4)

 Input Voltage, V  Control Voltage, V  Junction T emperature Range-------------------------------------------------------------------------------------------- −40°C to 125°C  Ambient T emperature Range-------------------------------------------------------------------------------------------- −40°C to 85°C

---------------------------------------------------------------------------------------------------------- 4.5V to 26V

------------------------------------------------------------------------------------------------------ 4.5V to 5.5V

Electrical Characteristics

(VCC = 5V, T

Input Power Supply

VCC Quiescent Supply Current

VCC Shutdown Current I CS Shutdown Curr ent CS pull to GND -- -- 1 A

FB Error Co mp arator Threshold

FB Input Bias Current V

= 25°C, unless otherwise specified)

Parameter Symbol Test Conditions Min Typ Max Unit

SHDN

FB forced above the regulation point, V

= 5V,

VCC current, VEN = 0V -- -- 1 A

-- 500 1250 A

DEM 0.7005 0.704 0.7075

REF

DEM, TA = 40 to 85C (Note 5) 0.697 0.704 0.711

= 0.735V 1 0.01 1 A

DS8237C/D-06 February 2014www.richtek.com

RT8237C/D

Parameter Symbol Test Conditions Min Typ Max Unit

Voltage Range 0.7 -- 3.3 V

OUT

RRF = 470k (Note 6) -- 290 --

Switc hing Fre quen cy f

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 Thresho ld DEM 10 -- 5 mV

Cu rrent Lim it T hr eshol d V

LIMIT

PHASE GND, VCS = 2.4V -- 300 --

Negative Current Limit Threshold

PHASE GND, VCS = 1.6V -- 200 - PHASE GND, V

Protection Function

Output UV Threshold

OVP Threshold OV Fault Delay FB forc ed above OV threshold -- 5 -- s VCC Under Voltage Lockout

Threshold V

Soft-Start From EN = high to V

OUT

UVLO

UV Blank Time From EN signal going high -- 3 -- ms Ther mal Shut dow n TSD -- 150 -- C

Driver On Resistance

UGATE Drive Source R UGATE Drive Sink R LGATE Drive Source R LGATE Drive Sink R

Dead Time

UGATEsr UGATEsk LGATEsr LGATEsk

LGATE R ising (V UGATE Rising -- 30 --

Internal Boost Charging Switch On Resistance

VCC to BOOT, 10 mA -- -- 8 0 

EN Threshold

EN Input Threshold Voltage

Logic-High VIH 1.8 -- -Logic-Low V

-- -- 0.5

RRF = 200k (Note 6) -- 340 --

kHz

RRF = 100k (Note 6) -- 380 -RRF = 39k (Note 6) -- 430 --

GND PHASE, V GND PHASE, VCS = 1.6V 185 200 215

= 2.4V 280 300 320

GND PHASE, VCS = 0.4V 40 50 60

= 0.4V -- 50 --

With respect to error comparator threshold

65 70 75 %

120 125 130 %

Falling edge, hysteresis = 100mV, PWM

3.7 3.9 4.1 V

disabled below this level

= 95% -- 1300 -- s

OUT

BOOT  PHASE forced to 5V -- 1.8 3.6 

BOOT PHA SE forced to 5V -- 1.2 2.4 

LG ATE, High State -- 1.8 3.6 

LGATE, Low State -- 0.8 1.6 

= 1.5V) -- 30 --

PHASE

DS8237C/D-06 February 2014 www.richtek.com

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

Tr ip Thres ho ld (fa lli ng, leaving PGOOD)

Trip Threshold (rising, leaving PGOOD)

Fault Propagation Delay Output Low Voltage I

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. θ

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 V

is measured at T

measured at the exposed pad of the package.

= 25°C on a low effective thermal conductivity single-layer test board per JEDEC 51-3. θJC is

Measured at FB, with respect to referenc e, Hysteresis = 3%

Measured at FB, with respect to reference,

Hys teresis = 3%

Falling Edge, FB forced below PGOOD trip threshold

= 1m A -- -- 0.4 V

SINK

= 8V, V

= 1.1V, I

OUT

= 10A using application circuit.

OUT

87 90 93 %

120 125 130 %

-- 2.5 -- s

DS8237C/D-06 February 2014www.richtek.com

+ 12 hidden pages

Richtek RT8237CZQW, RT8237DZQW Schematic [ru]

Specifications and Main Features

Frequently Asked Questions

User Manual