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STMicroelectronics Electronic Components Datasheet

L5971 Datasheet

1.5A STEP DOWN SWITCHING REGULATOR

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L5971 pdf
® L5971
1.5A STEP DOWN SWITCHING REGULATOR
UP TO 1.5A STEP DOWN CONVERTER
OPERATING INPUT VOLTAGE FROM 6.5V
TO 28V
PRECISE 1.26V (±1%) INTERNAL REFER-
ENCE VOLTAGE
OUTPUT VOLTAGE ADJUSTABLE FROM
1.26V TO 20V
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 L5971 is a step down monolithic power
switching regulator delivering 1.5A at a voltage
between 1.26V and 20V (selected by a simple
external 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: L5971 (Minidip)
L5971D (SO16)
A switching frequency up to 500KHz is achiev-
able (the maximum power dissipation of the pack-
ages must be observed).
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 SO16 for
SMD assembly.
Typical Applications:
- High efficiency step-down converter
- Portable computers
- Battery charger
- Distributed power
- PDAs and Mobile Comminicators
Vi=6V to 28V
C1
47µF
30V
5(11)
8(14)
R1
22K L5971
3(4) 4(5,6)
C2
1.2nF
2(3)
C5
47nF
7(13) 1(2) 6(12)
R2
9.1K
C4
22nF
C6
100nF
D1
STPS
3L40U
L1
30µH
C8
330µF
VO=2.5V/1.5A
R3
R4
May 2000
D98IN832C
1/11


STMicroelectronics Electronic Components Datasheet

L5971 Datasheet

1.5A STEP DOWN SWITCHING REGULATOR

No Preview Available !

L5971 pdf
L5971
BLOCK DIAGRAM
THERMAL
SHUTDOWN
VOLTAGES
MONITOR
2
SS_INH
INHIBIT
COMP
FB
7
8
E/A
1.26V
SOFTSTART
1.26V
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
D98IN833
GND
SS_INH
OSC
OUT
18
27
36
45
D97IN595
FB
COMP
BOOT
VCC
Minidip
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
OUT
5 11
VCC
6 12
BOOT
7 13
COMP
8 14
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
Not regulated 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 this pin to the output 1.26V is obtained; a
voltage divider is requested 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 L5971
Description 1.5A STEP DOWN SWITCHING REGULATOR
Maker STMicroelectronics
Total Page 11 Pages
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