November 2010 Doc ID 7332 Rev 9 1/11
11
L6902
Up to 1 A switching regulator with adjustable current limit
Features
■ Up to 1 A output current
■ Operating input voltage from 8 V to 36 V
■ Precise 3.3 V (±2%) reference voltage
■ 5 % output current accuracy
■ Output voltage adjustable from 1.235 V to 34 V
■ 250 kHz internally fixed frequency
■ Voltage feedforward
■ Zero load current operation
■ Adjustable current limit
■ Protection against feedback Disconnection
■ Thermal shutdown
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 and subnotebook
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
current error amplifier to have a constant voltage
and constant current control.
By means of an on board current sense resistor
and the availability of the current sense pins (both
compatible to Vcc and for Cs- compatible with
GND too) a current limit programming is very
simple and accurate (±5%). Moreover constant
current control can be used to charge NiMH and
NiCd batteries.
The device can be used as a standard DC/DC
converter with adjustable current limit (set by
using the external sense resistor).
The internal robust P-channel DMOS transistor
with a typical of 250 mΩ assures high efficiency
and a minimum dropout even at high output
current level. The internal limiting current (latched
function) of typical value of 2.5 A 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.
Other protections beside thermal shutdown
complete the device for a safe and reliable
application: overvoltage protection, frequency
folback overcurrent protection and protection vs.
feedback disconnection.
The internal fixed switching frequency of 250KHz,
and the SO-8 package pin allow to built an ultra
compact DC/ DC converter with a minimum board
space.
Table 1. Device summary
Order codes Package Packaging
L6902D
SO-8
Tube
L6902D013TR Tape and reel
SO-8
www.st.com
