MB3800

Document Number: 002-08716 Rev. *A

Page 13 of 21

10.3 Other Functions

10.3.1 Soft start and short circuit detection

On completion of soft start operation, the SCP pin (pin 2) stays low and enters the short circuit detection wait state. When an

approximately 0.8 V, the OUT pin (pin 5) is set low and the SCP pin (pin 2) stays low.

Once the protection circuit operates, the circuit can be restored by resetting the power supply. (See “How to Set the Time

Constant for Soft Start and Short Circuit Detection”.)

10.3.2 Circuit to prevent malfunction at low input voltage

Transients when powering on or instantaneous glitches in the supply voltage can lead to malfunction of the control IC and cause

system damage or failure. The circuit to prevent malfunction at low input voltage detects a low input voltage by comparing the

supply voltage to the internal reference voltage. On detection, the circuit fixes the OUT pin (pin 5) to low.

The system recovers when the supply voltage rises back above the threshold voltage of the malfunction prevention circuit.

11. Application Example

12. Notes On Use

malfunction.

1

2

4

3

8

7

6

5

MB3800

3 k

Ω

22

μH

10

μF

270

pF

0.1

μF

18 k

Ω

V o

(5 V)

2 k

Ω

0.1

μF

390

Ω

CTL

33

μF

+

+

V in

(3 V)

FB

OSC

GND

OUT

ÐIN

SCP

BR/CTL