October 2007 Rev 16 1/16
16
L5970D
Up to 1A step down switching regulator
Features
■ Up to 1A output current
■ Operating input voltage from 4.4V to 36V
■ 3.3V / (±2%) reference voltage
■ Output voltage adjustable from 1.2V to 35V
■ Low dropout operation: 100% duty cycle
■ 250KHz Internally fixed frequency
■ Voltage feedforward
■ Zero load current operation
■ Internal current limiting
■ Inhibit for zero current consumption
■ Synchronization
■ Protection against feedback disconnection
■ Thermal shutdown
Applications
■ Consumer: STB, DVD, TV, VCR, car radio,
LCD monitors
■ Networking: XDSL, modems, DC-DC modules
■ Computer: printers, audio/graphic cards,
optical storage, hard disk drive
■ Industrial: changers, car battery, DC-DC
converters
Figure 1. Test application circuit
Description
The L5970D is a step down monolithic power
switching regulator capable to deliver up to 1A at
output voltages from 1.2V to 35V.
The device uses an internal P-Channel D-MOS
transistor (with a typical Rdson of 250mΩ) as
switching element to minimize the size of the
external components.
An internal oscillator fixes the switching frequency
at 250KHz.
Having a minimum input voltage of 4.4V only, it is
particularly suitable for 5V bus, available in all
computer related applications.
Pulse by pulse current limit with the internal
frequency modulation offers an effective constant
current short circuit protection.
SO8
www.st.com
D98IN954C
8
2
4
5
1
7
L5970D
C1
10µF
35V
CERAMIC
C2
100µF
10V
VOUT=3.3V
VIN = 4.4V to 35V
R1
5.6K
R2
3.3K
R3
4.7K
C4
22nF
C3
220pF
3
6
D1
STPS2L40U
3.3V
INH.
SYNC.
COMP
VCC
VREF
OUT
FB
GND
L1 33µH
