Datasheet

PIN FUNCTIONS
N
o
Name Function
1 BOOTSTRAP A C
boot
capacitor connected between this terminal and the output allows to drive
properly the internal D-MOS transistor.
2 RESET DELAY A C
d
capacitor connected between this terminal and ground determines the reset
signal delay time.
3 RESET OUT Open Collector Reset/power Fail Signal Output. This output is high when the supply
and the output voltages are safe.
4 RESET INPUT Input of Power Fail Circuit. The threshold is 5.1V. It may be connected via a divider
to theinput for power fail function. Itmust be connected to the pin 14 an external 30KΩ
resistor when power fail signal not required.
5, 6
15, 16
GROUND Common Ground Terminal
7 FREQUENCY
COMPENSATION
A series RC network connected between this terminal and ground determines the
regulation loop gain characteristics.
8 SOFT START Soft Start Time Constant. A capacitor is connected between thi sterminal and ground
to define the soft start time constant.
9 FEEDBACK INPUT The Feedback Terminal of the Regulation Loop. The output is connected directly to
this terminal for 5.1V operation; It is connected via a divider for higher voltages.
10 SYNC INPUT Multiple L4972A’s are synchronized by connecting pin 10 inputs together or via an
external syncr. pulse.
11 SUPPLY VOLTAGE Unregulated Input Voltage.
12, 19 N.C. Not Connected.
13 V
ref
5.1V V
ref
Device Reference Voltage.
14 V
start
Internal Start-up Circuit to Drive the Power Stage.
17 OSCILLATOR R
osc
. External resistor connected to ground determines the constant charging current
of C
osc
.
18 OSCILLATOR C
osc
. External capacitor connected to ground determines (with R
osc
) the switching
frequency.
20 OUTPUT Regulator Output.
L4972A-L4972AD
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