Richtek RT9297GQW Schematic [ru]

®

3A High Performance Step-Up DC/DC Converter

RT9297

General Description

The RT9297 includes a high performance step-up DC/DC

converter that provides a regulated supply voltage for active-

matrix thin-film transistor (TFT) liquid-crystal displays

(LCDs).

The Boost Converter incorporates current mode, fixed-

frequency, pulse-width modulation (PWM) circuitry with

a built-in N-Channel power MOSFET to achieve high

efficiency and fast transient response.

The RT9297 is available in a WDFN -10L 3x3 package.

Ordering Information

RT9297

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

Lead Plating System
G : Green (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.

Features

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High Efficiency Up to 90%

z

zz

zz

z Adjustable Output Voltage : V

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z Wide Input Supply Voltage : 2.6V to 5.5V

zz

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z Input Under Voltage Lockout

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zz

z Pin-Programmable Switching Frequency 640kHz/

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to 24V

DD

1.2MHz

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z Programmable Soft-Start

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z Small 10-Lead WDFN Package

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z RoHS Compliant and Halogen Free

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Applications

z Notebook Computer Displays

z LCD Monitor Panels

z LCD TV Panels

Pin Configurations

(TOP VIEW)

COMP

FB

EN

GND
GND

1

2
3

4

5

10

SS

9

FREQ

8

VDD

GND

7

LX

11

6

LX

WDFN-10L 3x3

Marking Information

EZ= : Product Code

EZ=YM

YMDNN : Date Code

DNN

Typical Application Circuit

RT9297

VDD

FREQ
EN

COMP

L1

LX

FB

SS

GND

4, 5,
11 (Exposed Pad)

V

2.6V to 5.5V

Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.

©

DD

C3

C1

R3

8

9

3

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DS9297-02 June 2012 www.richtek.com

6, 7

2

10

D1

R1

C

SS

R2

C2

V

AVDD

1

RT9297

Function Block Diagram

EN

COMP

FB

1.24V

FREQ

Oscillator

4µA

Functional Pin Description

Pin No. Pin Name Pin Function

1 COMP

2 FB

Compensation Pin for Error Amplifier. Connect a series RC fr om CO MP to
ground.

Feedback. The feedback regulation voltage is 1.24V nominal. Connect an
external resistive voltage-divider between the step-up regulator’s output (V
and GND, with the center tap connected to FB. Place the divider close to the IC
and minimize the trace area to reduce noise coupling.

LX

V

IN

V

FB

Error
Amplifier

-

+

Slope

Compen-

sation

Protection

Summing
Comparator

Clock

4µA

Soft­Start

-

+

Control

and

Driver

Logic

Current

Sense

VDD

SS

LX

GND

AVDD

)

3 EN Enable Control Input. Drive EN low to turn off the Boost Converter.

4, 5

11 (Exposed Pad)

6, 7 LX

8 VDD Supply Pin. Bypass VDD with a minimum 1μF ceramic capacitor directly to GND.

9 FREQ

10 SS

GND

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

GND for maximum power dissipation.

Switch. LX is the drain of the internal MOSFET. Connect the inductor/rectifier
diode junction to LX and minimize the trace area for lower EMI.

Frequency-Select Input. When FREQ is low, the oscillator frequency will be set
to 640kHz. When FREQ is high, the frequency will be set to 1.2MHz. This input
has a 6μA pull-down current.

Soft-Start Control. Connect a soft-start capacitor (C

) to this pin. A 4μA

SS

constant current charges the soft-start capacitor. When EN connected to GND,
the soft-start capacitor is discharged. When EN connected to V
soft-start capacitor is charged to V

. Leave floating for not using soft-start.

DD

high, the

DD

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RT9297

Absolute Maximum Ratings (Note 1)

z LX to GND --------------------------------------------------------------------------------------------------------------- −0.3V to 26V
z Other Pins to GND ---------------------------------------------------------------------------------------------------- −0.3V to 6V

z Power Dissipation, P

WDFN-10L 3x3 --------------------------------------------------------------------------------------------------------- 1.667W

z Package Thermal Resistance (Note 2)

WDFN-10L 3x3, θJA--------------------------------------------------------------------------------------------------- 60°C/W

WDFN-10L 3x3, θJC--------------------------------------------------------------------------------------------------- 8.2°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 Model)------------------------------------------------------------------------------------------ 2kV

MM (Machine Model) ------------------------------------------------------------------------------------------------- 200V

Recommended Operating Conditions (Note 4)

z Supply Input Voltage, VDD ------------------------------------------------------------------------------------------ 2.6V to 5.5V
z Junction Temperature Range ---------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range ---------------------------------------------------------------------------------------- −40°C to 85°C

@ T

D

= 25°C

A

Electrical Characteristics

(VDD = 3.3V, T

Supply Current

Input Voltage Range VDD

Output Voltage Range V

Under-Voltage Lockout

Threshold

Quiescent Current IQ

Shutdown Current I

Oscillator

Oscillator Frequency f

Maximum Duty Cycle -- 90 -- %

Error Amplifier

Feedback Regulation Voltage VFB 1.22 1.24 1.26 V

Feedback Input Bias Current I

= 25°C, unless otherwise specified)

A

Parameter Symbol Test Conditions Min Typ Max Unit

V

< 18V 2.6 -- 5.5

AVDD

18V < V

VDD -- 24 V

AVDD

V

VDD Rising -- 2.4 -- V

UVLO

< 24V 4 -- 5.5

AVD D

V

Hysteresis -- 50 -- mV

V

= 1.3V, LX Not Switching -- 0.5 --

FB

V

= 1V, LX Switching -- 4 --

FB

EN = GND -- 0.1 10 μA

SHDN

mA

FREQ = GND 500 640 750

OSC

-- 125 250 nA

FB

FREQ = V

1000 1240 1500

lN

kHz

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RT9297

Parameter Symbol Test Conditions Min Typ Max Unit

Feedback Line Regulation -- 0.05 0.2 %/V
Transconductance gm ΔI = ±2.5μA at COMP = 1V -- 135 -- μA/V

Voltage Gain Av FB to COMP -- 700 -- V/V

N- MOSFET

Current Limit I

On-Resistance R

Leakage Current I

LIM

DS(ON)

LEAK

Current-Sense Transresistance RCS -- 0.25 -- V/A

Soft-Start

Charge Current ISS -- 4 -- μA

Control Inputs

EN, FREQ Input Low Voltage VIL -- -- 0.3 x VDD V

EN, FREQ Input High Voltage VIH 0.7 x VDD -- -- V

EN, FREQ Input Hysteresis -- 0.1 x VDD -- V
FREQ Pull-down Current -- 6 -- μA

EN Input Current IEN EN = GND -- 0.001 1 μA

3 3.8 5 A

-- 125 250 mΩ

VLX = 24V -- 30 45 μA

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.

is measured at T

JA

measured at the exposed pad of the package.

= 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is

A

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