L4974 STMicroelectronics, L4974 Datasheet - Page 3

• Manufacturer Part Number: L4974
• Description: 3.5A SWITCHING REGULATOR
• Manufacturer: STMicroelectronics

PIN FUNCTIONS
15, 16
12, 19
5, 6
N
10
11
13
14
17
18
20
1
2
3
4
7
8
9
o
BOOTSTRAP
RESET DELAY
RESET OUT
RESET INPUT
GROUND
FREQUENCY
COMPENSATION
SOFT START
FEEDBACK INPUT
SYNC INPUT
SUPPLY VOLTAGE
N.C.
V
V
OSCILLATOR
OSCILLATOR
OUTPUT
ref
start
Name
A C
frequency.
properly the internal D-MOS transistor.
A C
signal delay time.
Open Collector Reset/power Fail Signal Output. This output is high when the supply
and the output voltages are safe.
Input of Power Fail Circuit. The threshold is 5.1V. It may be connected via a divider
to the input for power fail function. It mustbe connected to the pin 14 an external 30K
resistor when power fail signal not required.
Common Ground Terminal
A series RC network connected between this terminal and ground determines the
regulation loop gain characteristics.
Soft Start Time Constant. A capacitor is connected between thi sterminal and ground
to define the soft start time constant.
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.
Multiple L4974A’s are synchronized by connecting pin 10 inputs together or via an
external syncr. pulse.
Unregulated Input Voltage.
Not Connected.
5.1V V
Internal Start-up Circuit to Drive the Power Stage.
R
of C
C
Regulator Output.
osc
osc
boot
d
. External resistor connected to ground determines the constant charging current
osc
. External capacitor connected to ground determines (with R
capacitor connected between this terminal and ground determines the reset
.
ref
capacitor connected between this terminal and the output allows to drive
Device Reference Voltage.
F unctio n
osc
) the switching
L4974A
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