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STMicroelectronics Electronic Components Datasheet

L4971D Datasheet

1.5A STEP DOWN SWITCHING REGULATOR

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L4971D pdf
® L4971
1.5A STEP DOWN SWITCHING REGULATOR
UP TO 1.5A STEP DOWN CONVERTER
OPERATING INPUT VOLTAGE FROM 8V TO
55V
PRECISE 3.3V (±1%) INTERNAL REFER-
ENCE 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)
INHIBIT FOR ZERO CURRENT CONSUMP-
TION
PROTECTION AGAINST FEEDBACK DIS-
CONNECTION
THERMAL SHUTDOWN
SOFT START FUNCTION
DESCRIPTION
The L4971 is a step down monolithic power
switching regulator delivering 1.5A at a voltage
between 3.3V and 50V (selected by a simple ex-
ternal divider). Realized in BCD mixed technol-
ogy, the device uses an internal power D-MOS
transistor (with a typical Rdson of 0.25) to ob-
tain very high efficency and high switching speed.
TYPICAL APPLICATION CIRCUIT
Minidip
SO16W
ORDERING NUMBERS: L4971 (Minidip)
L4971D (SO16)
A switching frequency up to 500KHz is achiev-
able (the maximum power dissipation of the pack-
ages must be observed).
A wide input voltage range between 8V to 55V
and output voltages regulated from 3.3V to 50V
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, soft-start, protection against
feedback loop disconnection, inhibit for zero cur-
rent consumption 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
C1
220µF
63V
C7
220nF
R1
20K
C2
2.7nF
C5
100nF
5
8
L4971
3
4
27
16
L1
126µH
(77120)
VO=3.3V/1.5A
R2
9.1K
C4
22nF
C6
100nF
D1
GI
SB360
C8
330µF
D97IN748A
May 2000
1/12


STMicroelectronics Electronic Components Datasheet

L4971D Datasheet

1.5A STEP DOWN SWITCHING REGULATOR

No Preview Available !

L4971D pdf
L4971
BLOCK DIAGRAM
THERMAL
SHUTDOWN
VOLTAGES
MONITOR
2
SS_INH
INHIBIT
COMP
FB
7
8
E/A
3.3V
SOFTSTART
3.3V
INTERNAL
REFERENCE
PWM
R
Q
S
OSCILLATOR
PIN CONNECTIONS
3
OSC
1
GND
VCC
5
INTERNAL
SUPPLY 5.1V
DRIVE
CBOOT
CHARGE
6
BOOT
CBOOT
CHARGE
AT LIGHT
LOADS
4
OUT
D97IN594
GND
SS_INH
OSC
OUT
18
27
36
45
D97IN595
Minidip
FB
COMP
BOOT
VCC
N.C.
GND
SS_INH
OSC
OUT
OUT
N.C.
N.C.
1 16
2 15
3 14
4 13
5 12
6 11
7 10
89
D97IN596
SO16W
N.C.
N.C.
FB
COMP
BOOT
VCC
N.C.
N.C.
PIN FUNCTIONS
DIP SO (*)
12
23
Name
GND
SS_INH
34
OSC
4 5, 6
5 11
6 12
OUT
VCC
BOOT
7 13
8 14
COMP
FB
Function
Ground
A logic signal (active low) disables the device (sleep mode operation).
A capacitor connected between this pin and ground determines the soft start time.
When this pin is grounded disables the device (driven by open collector/drain).
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 DMOS
Transistor
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.
2/12


Part Number L4971D
Description 1.5A STEP DOWN SWITCHING REGULATOR
Maker STMicroelectronics
Total Page 12 Pages
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