Richtek RT9268PE Schematic [ru]

Preliminary

RT9268

Tiny Package, 1.3MHz, Step-up DC/DC Converter

General Description

The RT9268 is a compact, 1.3MHz, step-up DC/DC
converter with a current mode PWM control loop,
providing a stable and ef ficient operation without external
compensation.

The high switching frequency makes RT9268 suitable
for ADSL applications providing sufficient output current
for variant types of line drivers. This device is available
in space-saving SOT -23-6 package.

The output voltage is set with 2 external resistors. Both
internal 2A switch and driver for driving external power
devices (NMOS or NPN) are provided.

Ordering Information

RT9268

Package Type
E : SOT-23-6

Operating Temperature Range
C : Commercial Standard
P : Pb Free with Commercial Standard

Note :
RichTek Pb-free 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.

−100%matte tin (Sn) plating.

Marking Information

Features

zz

1.3MHz Switching Frequency

z

zz

zz

z Below 2V Low Start-up Input Voltage

zz

zz

z Sufficient Supply Capability for Supplying XDSL

zz

Line Drivers

zz

z Zero Shutdown Mode Supply Current

zz

zz

z Providing Flexibility for Using Internal and Extern al

zz

Power Switches

z Small SOT-23-6 Package

zz

z RoHS Compliant and 100% Lead (Pb)-Free

zz

Applications

z XDSL Line Drivers
z USB Devices
z PCMCIA Cards
z Mini-PCI Cards

Pin Configurations

(TOP VIEW)

FB VDD

1

EN

SOT-23-6

Note : There is no pin1 indicator on top mark for SOT-23-6
type, and pin 1 will be lower left pin when reading top mark
from left to right.

LX

4

56

23

GND

EXT

For marking information, contact our sales re presentative
directly or through a RichTek distributor located in your
area, otherwise visit our website for detail.

DS9268-06 March 2005 www.richtek.com

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RT9268

Typical Application Circuit

V

IN

0.3V to 5.5V

C1

1uF

VDD

EN

Figure 1. RT9268 Application for XDSL 18V Line Drivers

C2
10uF

RT9268

GND

Preliminary

L1

3.3uF

C3
1uF

EXT

LX
FB

L2 : CL321611T-R22K-S/ YAGEO

D1

Q1
N MOS

L2

C4

0.1uF

R1
12k

R2
910

C5

1uF

+

C6

10uF

V

18V

OUT

V

IN

4.5V to 5.2V

C1

1uF

L1

3.3uF

VDD

EN

C2
10uF

EXT

RT9268

GND

C3
1uF

LX
FB

D1

Q1
N MOS

L2

D2

C4

0.1uF

D3

C8

10uF

R1

8.6K

R2
1k

C5

1uF

L2 : CL321611T-R22K-S/ YAGEO

Figure 2. RT9268 Application for USB-XDSL ±12V Line Drivers

+

V

OUT2

-12V

C6

10uF

V

12V

OUT1

DS9268-06 March 2005www.richtek.com

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Functional Pin Description

Preliminary

RT9268

Pin No. Pin Name

1 EN
2 EXT
3 GND
4 LX
5 VDD
6 FB

Pin Function

Chip Enable (Active High)
Output Pin for Driving External NMOS
Ground
Pin for Switching
Input Positive Power Pin of RT9268
Feedback Input Pin Internal refe rence voltage for the error amplifie r is 1.25V.

Function Block Diagram

VDD

FB

1.25V
VDD

-

Loop Control Circuit

+

RT9268

EXT
LX

Q1
N MOS

R1

EN

R2

Q2
N MOS

Over Temp.

Detector

Shut Down

GND

DS9268-06 March 2005 www.richtek.com

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