richtek RT8241D Datasheet

RT8241D

High Efficiency Single Synchronous Buck PWM Controller

General Description

The RT8241D 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 RT8241D supports on chip voltage programming function between 0.675V and 0.9V by controlling GX digital inputs.

The constant-on-time PWM control sche me handles 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 RT8241D a chieves 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 RT8241D is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as

0.675V.

Features

z Meet Intel VCCSA Voltage Slew Rate z Built-in 1% Reference Voltage z 2-Bit Programma ble Output V oltage with Integrated

Tra n sition Support

z Quick Load-Step Response within 100ns z 4700ppm/

Side R

z 4.5V to 26V Battery Input Range z Internal Ramp Current Limit Soft-Start Control z Drives Large Synchronous Rectifier FET s z Integrated Boost Switch z Over/Under Voltage Protection z Thermal Shutdown z Power Good Indicator z RoHS Compliant and Halogen Free

°°

°C Programmable Current Limit by Low

°°

Sensing

DS(ON)

Applications

z Notebook Computers z CPU/GPU Core Supply z Chipset/RAM Supply z Generic DC/DC Power Regulator

Pin Configurations

The RT8241D is availa ble in a WQF N-12L 2x2 package.

Ordering Information

RT8241D

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

Lead Plating System

LGATE PGOOD

PHASE UGATE

(TOP VIEW)

GND

12 1011

GND

2 3

654

9 8

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 require-

ments of IPC/JEDEC J-STD-020.

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

DS8241D-03 January 2014 www.richtek.com

WQFN-12L 2x2

VCC

BOOT

RT8241D

Marking Information

RT8241DGQW

38 : Product Code

38W

Typical Application Circuit

For Fixed V oltage Regulator :

W : Date Code

RT8241DZQW

38W

38 : Product Code W : Date Code

Chip Enable

* : Optional

12, 13 (Exposed Pad)

For Adjustable Voltage Regulator :

Chip Enable

* : Optional

12, 13 (Exposed Pad)

BYPASS

RT8241D

VCC

PGOOD

GND

RT8241D

VCC

PGOOD

GND

BOOT

UGATE

PHASE

LGATE

G0 G1 FB

BOOT

UGATE

PHASE

LGATE

G0 G1 FB

1 7

8 10

1 7

8 10

R5*

C2*

R5*

C2*

OUT

FB1

FB2

C3*

OUT

Table 1. VID Table

G0 G1 VFB

0 0 0.9V 0 1 0.8V 1 0 0.725V 1 1 0.675V

DS8241D-03 January 2014www.richtek.com

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

2 PHASE

3 UGATE Gate Drive Output for the High Side External MOSFET. 4 BOOT

5 VCC

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. High impedance indicates power is good.

10 FB Output Voltage Feedback Input. 11 CS

12, 13 (Exposed Pad) GND

cur rent se nse co mpar ator inp ut for lo w sid e MOSFET R reference voltage for on time generation.

Su pply In put for High S ide Dr iver. C onnec t a capa citor t o the f loating node (PHASE) pin.

Control Voltage Input. Provides the power for the buck controller, the low side dr iver a nd t he bo otstr ap c ircuit for high s ide d river . Bypa ss to GN D with a

4.7μF ceramic capacitor .

Cu r rent L im it T hre sh old Sett in g Inp ut. C on nec t a se tt in g res ist or to G ND an d the current limit threshold is equal to 1/8 of the voltage seen at this pin.

Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissip ation.

RT8241D

sensi ng and

DS(ON)

Function Block Diagram

TRIG

On-time compute

1.1V

0.45V

85% V

REF

One shot

PHASE

(Internal)

Voltage

Programmer

REF

COMP

Latch

S1 Q

Latch

S1 Q

TON

Shutdown

Thermal

Min toff

One shot

Emulation

TRIGQ

Diode

ZCD

BST switch resistance

DRV

1/8

OC threshold

UG R

LG R

leakage

DS(ON)

10µA

BOOT UGATE PHASE

VCC LGATE GND

PGOOD

DS8241D-03 January 2014 www.richtek.com

RT8241D

Absolute Maximum Ratings

z VCC, FB, PGOOD, EN, CS, G0, G1 to GND ----------------------------------------------------------------------- −0.3V to 6V z PHASE to GND

(Note 1)

DC----------------------------------------------------------------------------------------------------------------------------- −0.3V to 32V <20ns ------------------------------------------------------------------------------------------------------------------------ −8V to 38V

z BOOT to PHASE ----------------------------------------------------------------------------------------------------------- −0.3V to 6V z UGATE to PHASE

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

z LGA TE to GND

z Power Dissipation, P

@ T

= 25°C

WQFN-12L 2x2 ------------------------------------------------------------------------------------------------------------ 0.606W

z Package Thermal Re sistance (Note 2)

WQFN-12L 2x2, θJA------------------------------------------------------------------------------------------------------- 165 °C/W

z Junction T emperature----------------------------------------------------------------------------------------------------- 150°C z Lead Temperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°C z Storage T emperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C z ESD Susceptibility (Note 3)

HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV MM (Ma chine Mode)------------------------------------------------------------------------------------------------------ 200V

Recommended Operating Conditions (Note 4)

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

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

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

Electrical Characteristics

= 5V, V

PWM Controller

VCC Quiescent Supply Current IQ VCC Shutdown Current I

CS Shutdown Curr ent CS pull to GND -- -- 1 μA FB Error Comparator Threshold VFB V

Voltage Range V

OUT

On -Time, Pulse Width tON VFB = 0.9V (f

Minimum Off-Time t

= 8V, V

= 5V, V

= 1V, T

= 25°C, unless otherwise specified)

Parameter Symbol Test Conditions Min Typ Max Unit

FB forced above the regulation point, V

VCC curren t , V

SHDN

= 5 V

= 0V -- -- 1 μA

TA = 25°C −1 0 1 T

= −40°C to 85°C (Note 5) −1.5 0 1.5

0.675 -- 3.3 V

OUT

= 300kHz) -- 40 0 -- ns

OFF

-- 500 1250 μA

250 400 550 ns

DS8241D-03 January 2014www.richtek.com

RT8241D

Parameter Symbol Test Conditions Min Typ Max Unit

Current Se nsing

CS Source Current 9 10 11 μA CS Source Current

Temperature Coefficient Zero Crossing Threshold

Protection Function

Curr ent Limit Threshold Offset Negative Current Limit Threshold Offset

Under Voltage Protection UVP Detect, Falling Edge 0.41 0.45 0.49 V UVP Fault Delay VFB = 0.375V -- 3.5 -- μs Over Voltage Protection OVP Detect, Rising Edge 1.065 1.1 1.133 V OVP Fault Delay VFB = 1.183V -- 5 -- μs

VCC Under Voltage Lockout (UVLO) Threshold

VCC UVLO Hysteresis ΔV VOUT Soft-Start F rom EN = High to V Dynamic VID Slew Rate SGX G0/G1 Transition 1.75 -- 10 mV/μs

-- 4700 -- ppm/°C PHASE − GND −10

-- 5 mV

GND − PHASE = VCS/ 8 −20 0 20 mV

PHASE − GND = VCS/8 -- 3 -- mV

Falling edge, PWM disabled below

UVLO

this le v el

-- 100 -- mV

UVLO

= 95% -- 0.8 -- ms

OUT

3.5 3.7 3.9 V

UVP Blank Time From EN sig nal going h igh -- 3 - ms Therma l Shutdow n TSD -- 150 --

Therma l Shutdow n Hysteresis

-- 10 --

ΔT

°C

Driver On-Resistance

UGATE Driver Source

UGATE Driv er Sink LGATE Driver Source

LGATE Driver Sink

Dead Time Internal Boost Charging

Switch On-Resistance

UGATEsr

UGATEsk

LGATEsr

LGATEsk

VCC to BOOT, 10mA

BOOT−PHASE forced to 5V, UGATE High State BOOT−PHASE forced to 5V, UGATE Low State

LGATE, High State LGATE, Low State LGATE Rising (V

= 1.5V) --

PHASE

UGATE Rising

-- 1.8 3.6

-- 1.2 2.4 Ω

-- 1.8 3.6

-- 0.8 1.34 30

EN Threshold EN Threshold

Voltage

Logic-High Logic-Low

1.8 -- --

-- -- 0.5

Voltag e Programming (G0, G1) G0, G1 Input

Threshold Voltage

Logic-High 750 -- --

Logic-Low -- -- 300

Ω Ω

DS8241D-03 January 2014 www.richtek.com

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richtek RT8241D Datasheet

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