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L4976 Datasheet

1A STEP DOWN SWITCHING REGULATOR

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® L4976
1A STEP DOWN SWITCHING REGULATOR
UP TO 1A STEP DOWN CONVERTER
OPERATING INPUT VOLTAGE FROM 8V TO
55V
PRECISE 5.1V REFERENCE VOLTAGE
OUTPUT VOLTAGE ADJUSTABLE FROM
3.3V TO 50V
SWITCHING FREQUENCY ADJUSTABLE UP
TO 500KHz
VOLTAGE FEEDFORWARD
ZERO LOAD CURRENT OPERATION
INTERNAL CURRENT LIMITING (PULSE-BY-
PULSE AND HICCUP MODE)
PROTECTION AGAINST FEEDBACK DIS-
CONNECTION
THERMAL SHUTDOWN
DESCRIPTION
The L4976 is a step down monolithic power
switching regulator delivering 1A at a voltage be-
tween 3.3V and 50V (selected by a simple exter-
nal divider). Realized in BCD mixed technology,
the device uses an internal power D-MOS transis-
tor (with a typical Rdson of 0.25) to obtain very
high efficency and high switching speed.
A switching frequency up to 250KHz is achiev-
able (the maximum power dissipation of the pack-
TYPICAL APPLICATION CIRCUIT
Minidip
SO16W
ORDERING NUMBERS: L4976 (Minidip)
L4976D (SO16)
ages must be observed).
A wide input voltage range between 8V to 55V
and output voltages regulated from 3.3V to 40V
cover the majority of today’s applications.
Features of this new generations of DC-DC con-
verter include pulse-by-pulse current limit, hiccup
mode for short circuit protection, voltage feedfor-
ward regulation, protection against feedback loop
disconnection and thermal shutdown.
The device is available in plastic dual in line,
MINIDIP 8 for standard assembly, and SO16W
for SMD assembly.
Vi=8V to 55V
5
8
R1
20K L4976
3
4
C1 C7
220µF 220nF
C2
2.7nF
2
7
16
63V
L1
260µH
(77120)
VO=3.3V/1A
R2
9.1K
C4
22nF
C6
100nF
D1
GI
SB360
C8
330µF
May 2000
1/11


STMicroelectronics Electronic Components Datasheet

L4976 Datasheet

1A STEP DOWN SWITCHING REGULATOR

No Preview Available !

L4976
BLOCK DIAGRAM
THERMAL
SHUTDOWN
VOLTAGES
MONITOR
VREF
2
VREF
COMP
FB
7
8
E/A
3.3V
INTERNAL
5.1V REFERENCE
PWM
3.3V
R
Q
S
OSCILLATOR
PIN CONNECTIONS
3
OSC
1
GND
VCC
5
CBOOT
CHARGE
DRIVE
6
BOOT
CBOOT
CHARGE
AT LIGHT
LOADS
4
OUT
GND
VREF
OSC
OUT
1
2
3
4
8 FB
7 COMP
6 BOOT
5 VCC
Minidip
N.C.
GND
VREF
OSC
OUT
OUT
N.C.
N.C.
1 16
2 15
3 14
4 13
5 12
6 11
7 10
89
SO16W
N.C.
N.C.
FB
COMP
BOOT
VCC
N.C.
N.C.
PIN FUNCTIONS
DIP SO (*)
12
23
34
Name
GND
VREF
OSC
4 5, 6
OUT
5 11
VCC
6 12
BOOT
7 13
COMP
8 14
FB
Function
Ground
5.1V Reference voltage with 20mA current capability.
An external resistor connected between the unregulated input voltage and this pin and
a capacitor connected from this pin to ground fix the switching frequency. (Line feed
forward is automatically obtained)
Stepdown regulator output
Unregulated DC input voltage
A capacitor connected between this pin and OUT allows to drive the internal VDMOS
E/A output to be used for frequency compensation
Stepdown feedback input. Connecting directly to this pin results in an output voltage of
3.3V. An external resistive divider is required for higher output voltages.
(*) Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die.
2/11


Part Number L4976
Description 1A STEP DOWN SWITCHING REGULATOR
Maker STMicroelectronics
Total Page 11 Pages
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