BD9B301MUV-LB Datasheet, PDF (23/33 Pages) Rohm – Over Current Protection

BD9B301MUV-LB
Datasheet
3. Soft Start Setting
Turning the EN terminal signal High activates the soft start function. This causes the output voltage to rise gradually
while the current at startup is placed under control. This allows the prevention of output voltage overshoot and inrush
current. The rise time depends on the value of the capacitor connected to the SS terminal.
T_SS
C _SS V _FB /I _SS
C _SS
I _SS T_SS /V _FB
Where :
T_SS is Soft Start Time
C _SS is Capacitor connected to Soft Start Time Terminal
V _FB is FB Terminal Voltage (0.8V (Typ))
I _SS is Soft Start Terminal Source Current (1.0μA(Typ))
with C _SS 0.01 μF ,
T_SS 0.01μF 0.8 V)/1.0μA
8.0 msec 
Turning the EN terminal signal High with the SS terminal open or with the terminal signal High (no capacitor
connected) causes the output voltage to rise in 1msec (Typ).
4. FB Capacitor
Generally, in fixed ON time control (hysteresis control), sufficient ripple voltage in FB voltage is needed to operate
comparator stably. Regarding this IC, by injecting ripple voltage to FB voltage inside IC it is designed to correspond
to low ESR output capacitor. Please set the FB capacitor within the range of the following expression to inject an
appropriate ripple.
V_OUT
f _SW
1
‐
V_OUT
V _IN
7.5 10 ³
C _FB
V_OUT
f _SW
1
‐
V_OUT
V _IN
3.6 10 ³
Where :
VIN is Input Voltage
VOUT is Output Voltage
fSW is Switching Frequency
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TSZ02201-0J3J0AJ00830-1-2
2015.04.02 Rev.001