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RT8241

®

DS8241-03   January  2014

www.richtek.com

1

©

Copyright   2014 Richtek Technology Corporation. All rights reserved.                          is a registered trademark of Richtek Technology Corporation.

High Efficiency Single Synchronous Buck PWM Controller

General Description

The RT8241 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 RT8241 supports on chip voltage programming function

between 0.675V and 0.9V by controlling GX digital inputs.

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 RT8241 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 RT8241 is intended for CPU core,

chipset, DRAM, or other low voltage supplies as low as

0.675V.

The RT8241 is available in a WQFN-12L 2x2 package.

Features

z

Meet Intel VCCSA Voltage Slew Rate

z

Built-in 1% Reference Voltage

z

2-Bit Programmable Output Voltage with Integrated

Transition Support

z

Quick Load-Step Response within 100ns

z

4700ppm/

°°°°°

C  Programmable Current Limit by Low

Side R

DS(ON)

 Sensing

z

4.5V to 26V Battery Input Range

z

Internal Ramp Current Limit Soft-Start Control

z

Drives Large Synchronous Rectifier FETs

z

Integrated Boost Switch

z

Over/Under Voltage Protection

z

Thermal Shutdown

z

Power Good Indicator

z

RoHS Compliant and Halogen Free

Pin Configurations

(TOP VIEW)

WQFN-12L 2x2

Ordering Information

Applications

z

Notebook Computers

z

CPU/GPU Core Supply

z

Chipset/RAM Supply

z

Generic DC/DC Power Regulator

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.

LGATE

PGOOD

UGATE

PHASE

G0

G1

BOOT

VC

C

EN

GN

D

CS

FB

6

5

4

12

10

11

1

2

3

9

8

7

GND

13

RT8241

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)

Switching Frequency Operation
A : 300kHz
B : 400kHz
C : 500kHz

Summary of Contents for RT8241

Page 1: ...n high voltage batteries at the highest possible efficiency The RT8241 is intended for CPU core chipset DRAM or other low voltage supplies as low as 0 675V The RT8241 is available in a WQFN 12L 2x2 pa...

Page 2: ...LOUT 8 G1 VIN CIN VOUT COUT Optional R2 Chip Enable VCC RT8241 VCC 5 9 6 PGOOD EN 11 CS 12 13 Exposed Pad GND 4 BOOT 3 2 1 7 10 UGATE PHASE LGATE G0 FB R1 CBYPASS RCS R3 C1 R4 Q1 Q2 R5 C2 LOUT 8 G1 VI...

Page 3: ...d the bootstrap circuit for high side driver Bypass to GND with a 4 7 F ceramic capacitor 6 EN Chip Enable Active High 7 G0 2 Bit Input Pin 8 G1 2 Bit Input Pin 9 PGOOD Open Drain Power Good Indicator...

Page 4: ...C to 150 C z ESD Susceptibility Note 3 HBM Human Body Mode 2kV MM Machine Mode 200V Recommended Operating Conditions Note 4 z Supply Input Voltage VIN 4 5V to 26V z Control Voltage VCC 4 5V to 5 5V z...

Page 5: ...er Voltage Lockout UVLO Threshold VUVLO Falling edge PWM disabled below this level 3 5 3 7 3 9 V VCC UVLO Hysteresis VUVLO 100 mV VOUT Soft Start From EN High to VOUT 95 0 8 ms Dynamic VID Slew Rate S...

Page 6: ...1 A Note 1 Stresses listed as the above Absolute Maximum Ratings may cause permanent damage to the device These are for stress ratings Functional operation of the device at these or any other conditi...

Page 7: ...Frequency kHz 1 VIN 8V VCC VEN 5V VOUT 0 9V Efficiency vs Output Current 60 65 70 75 80 85 90 95 100 0 001 0 01 0 1 1 10 Output Current A Efficiency VIN 12V VCC VEN 5V VOUT 0 9V Switching Frequency vs...

Page 8: ...V VCC VEN 5V VOUT 0 8V to 0 9V VOUT 50mV Div 0 9V Shutdown Current vs Input Voltage 0 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 0 5 7 9 11 13 15 17 19 21 23 25 Input Voltage V Shutdown Current A 1 NoLoa...

Page 9: ...ransient Response Time 100 s Div VIN 12V VCC VEN 5V VOUT 0 9V ILOAD 0A to 6A ILOAD 5A Div VOUT_ac 20mV Div LGATE 10V Div UGATE 20V Div Over Voltage Protection PGOOD 5V Div VOUT 500mV Div LGATE 5V Div...

Page 10: ...this capacitor to charge from zero volts to VOUT thereby making the on time of the high side switch directly proportional to the output voltage and inversely proportional to the input voltage The imp...

Page 11: ...trigger NOCP the low side MOSFET will be turned off to prevent Figure 3 Output Voltage Down Transition LGATE PHASE UGATE FB G0 G1 G0 G1 Q1 Q2 CIN VIN RFB1 RFB2 BOOT VOUT COUT For an upward transition...

Page 12: ...e CS trip CS CS V mV R k 10 A The Inductor current can be monitored by the voltage between GND and the PHASE pin Hence the PHASE pin should be connected to the drain terminal of the low side MOSFET IC...

Page 13: ...e MOSFET without degrading the turn off time as shown in Figure 7 Figure 7 Reducing the UGATE Rise Time PHASE UGATE Q1 CIN VIN BOOT R Power Good Output PGOOD The power good output is an open drain out...

Page 14: ...nd cause erratic and unstable operation However it is easy to add sufficient series resistance by placing the capacitors a couple of inches downstream from the inductor and connecting FB divider close...

Page 15: ...ines should be strictly followed Connect an RC low pass filter from VCC 1 F and 10 are recommended Place the filter capacitor close to the IC Keep current limit setting network as close as possible to...

Page 16: ...ccurate 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...

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