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L6902D

October 2004

1

FEATURES

■

UP TO 1A OUTPUT CURRENT

■

OPERATING INPUT VOLTAGE FROM 8V TO 36V

■

PRECISE 3.3V (±2%) REFERENCE VOLTAGE

■

5% OUTPUT CURRENT ACCURACY

■

OUTPUT VOLTAGE ADJUSTABLE FROM

1.235V TO 34V

■

250KHz INTERNALLY FIXED FREQUENCY

■

VOLTAGE FEEDFORWARD

■

ZERO LOAD CURRENT OPERATION

■

ADJUSTABLE CURRENT LIMIT

■

PROTECTION AGAINST FEEDBACK

DISCONNECTION

■

THERMAL SHUTDOWN

2

APPLICATIONS

■

CHARGERS FOR NiCd, NiMH BATTERIES

AND PREREGULATOR FOR LITHIUM-ION

BATTERIES

■

ADJUSTABLE CURRENT GENERATOR

■

SIMPLE STEP-DOWN CONVERTERS WITH

ADJUSTABLE CURRENT LIMIT

■

BATTERY EQUIPPED SYSTEMS

■

DISTRIBUTED POWER SUPPLY

■

MOBILE PC & SUBNOTEBOOK

3

DESCRIPTION

The L6902D is a complete and simple step down

switching regulator with adjustable current limit.

Based on a voltage mode structure it integrates a cur-

rent error amplifier to have a constant voltage and con-

stant current control.

By means of an on board current sense resistor and

the availability of the current sense pins (both com-

patible to Vcc and for Cs- compatible with GND too)

a current limit programming is very simple and accu-

rate (±5%). Moreover constant current control can be

used to charge NiMH and NiCd batteries.

The device can be used as a standard DC/DC con-

verter with adjustable current limit (set by using the

external sense resistor).

The internal robust P-Channel DMOS transistor with a

typical of 250m

Ω assures high efficiency and a mini-

mum dropout even at high output current level. The in-

ternal limiting current (latched function) of typical value

of 2.5A protects the device from accidental output short

circuit avoiding dangerous loads damage.

If the temperature of the chip goes higher than a fixed

internal threshold (150°C with 20°C hysteresis), the

power stage is turned off.

UP TO 1A SWITCHING REGULATOR WITH

ADJUSTABLE CURRENT LIMIT

Figure 2. Test And Application Circuit

L1 22

µH

OUT

C1

10

µF

25V

CERAMIC

C3

220pF

C2

22nF

D1

STPS340U

R3

5.1K

C4

100

µF

10V

POSCAP

R1

5.6K

100m

Ω

R2

3.3K

3.3V

COMP

VREF

GND

FB

D01IN1306A

8

6

4

2

3

5

1

7

Rev. 8

Figure 1. Package

Table 1. Order Codes

Part Number

Package

L6902D

SO-8

L6902D013TR

SO-8 in Tape & Reel

SO-8