Primary Regulators

4

35

1

2

PQ1PF1

PQ1PF1

Output current

2.8V

3.6V

7.7V

0

Overcurrent

detection

Overload shut-down

3-2 Overcurrent protection function

Overcurrent protection circuit is shown in Fig.2. Fig.3 shows timing chart of OFF control process after detecting overcurrent.

First, drain current of MOS-FET (which is built-in device) is getting high due to overcurrent. When it comes up to overcurrent

by-pulse. Minimizing output pulse width makes output voltage lower. As output voltage is lowered, collector-emitter voltage of

charged again by 10

supply of IC becomes OFF-state and maintain shut-down state. To maintain output shut-down condition, 0.3mA (Vcc=11V) TYP.

Fig.2 Overcurrent Protection Circuit

Fig.3 Timing Chart Overcurrent Protection