MB3800 Fujitsu Microelectronics, Inc., MB3800 Datasheet - Page 7

• Manufacturer Part Number: MB3800
• Description: Switching Regulator Controller (low Voltage)
• Manufacturer: Fujitsu Microelectronics, Inc.

1. Soft Start
At power on, the capacitor C
start setting voltage as a proportion of the voltage at the SCP pin with the sawtooth waveform. The comparison
controls the ON duty of the OUT pin, causing the soft start operation. On completion of soft start operation, the
voltage at the SCP pin stays low, the soft start setting voltage stays high, and the circuit enters the output short
circuit detection wait state.
Soft start time (The time until the output ON duty reaches approximately 50%)
2. Short Circuit Protection
If the switching regulator output suddenly drops due to load effect, the error amplifier output (FB pin) is fixed at
VOM
pin is set low and the SCP pin stays low.
Once the protection circuit operates, the circuit can be restored by resetting the power supply.
• Short circuit detection time
HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT
DETECTION
+
t
and capacitor C
t
S
PE
[s]
[s]
0.35
0.8
C
C
PE
PE
PE
[ F]
[ F]
starts charging. When the voltage at the SCP pin reaches approximately 0.8V, the output
PE
connected to the SCP pin starts charging. The PWM comparator compares the soft
MB3800
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