L4978
BLOCK DIAGRAM
VCC
5
THERMAL
SHUTDOWN
VOLTAGES
MONITOR
CBOOT
CHARGE
SS_INH
2
INHIBIT
SOFTSTART
3.3V
COMP
FB
7
8
E/A
INTERNAL
REFERENCE
INTERNAL
SUPPLY
5.1V
6
PWM
BOOT
R
S
3.3V
Q
DRIVE
OSCILLATOR
1
GND
CBOOT
CHARGE
AT LIGHT
LOADS
3
OSC
4
OUT
D97IN594
PIN CONNECTIONS
N.C.
GND
1
2
3
4
5
6
7
8
D97IN596
16
15
14
13
12
11
10
9
N.C.
N.C.
FB
COMP
BOOT
VCC
N.C.
N.C.
GND
SS_INH
OSC
OUT
1
2
3
4
D97IN595
8
7
6
5
FB
COMP
BOOT
VCC
SS_INH
OSC
OUT
OUT
N.C.
N.C.
Minidip
SO16W
PIN FUNCTIONS
DIP
1
2
SO (*)
2
3
Name
GND
SS_INH
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
Transistors
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.
3
4
OSC
4
5
6
7
8
5, 6
11
12
13
14
OUT
V
CC
BOOT
COMP
FB
(*) Pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die.
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