L4978

2/13

Table 2. Block Diagram

Figure 3. Pins Connection (Top view)

Table 3. Pin Description

N°

Pin

Name

Function

1

2

GND

Ground

2

3

SS_INH

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).

3

4

OSC

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)

INHIBIT

SOFTSTART

VOLTAGES

MONITOR

THERMAL

SHUTDOWN

E/A

PWM

3.3V

OSCILLATOR

R

S

Q

INTERNAL

REFERENCE

INTERNAL

SUPPLY

3.3V

5.1V

DRIVE

CBOOT

CHARGE

CBOOT

CHARGE

AT LIGHT

LOADS

2

7

8

FB

COMP

SS_INH

3

1

4

6

5

BOOT

OSC

GND

OUT

VCC

D97IN594

GND

SS_INH

OSC

OUT

1

3

2

4

VCC

BOOT

COMP

FB

8

7

6

5

D97IN595

N.C.

GND

SS_INH

OSC

OUT

N.C.

OUT

N.C.

N.C.

N.C.

BOOT

VCC

COMP

FB

N.C.

N.C.

1

3

2

4

5

6

7

8

14

13

12

11

10

9

15

16

D97IN596

DIP-8

SO16W