MB39A106 Datasheet, PDF (21/46 Pages) Fujitsu Component Limited. – 2-Channel DC/DC Converter IC with Overcurrent Protection Symmetrical-Phase Type

MB39A106
3. Setting Overvoltage Detection by the Timer-Latch Overvoltage Protection Circuit
An overvoltage output from the DC/DC converter can be detected by connecting external resistors from the DC/
DC converter output to the noninverted input terminal (-INE1 terminal (pin 1) and -INE2 terminal (pin 15)) of the
overvoltage comparators (OVP Comp. 1 and OVP Comp. 2).
When the DC/DC converter output voltage exceeds the overvoltage detection level, the output of the overvoltage
comparator (OVP Comp. 1 and OVP Comp. 2) becomes the “H” level and the overvoltage protection circuit
actuates the timer circuit to start charging the external capacitor Cscp connected to the CSCP terminal (pin 11).
If the overvoltage remains applied beyond setting time, the circuit sets the latch to turn off the FET on the main
side of each channel while setting the PWRGOOD terminal (pin 12) to the “L” level. The protection circuit closes
both channels even when an overvoltage is detected on only either.
Overvoltage detection voltage : VOVP
VOVP (V) =: 1.38 × (R1 (Ω) + R2 (Ω) ) / R2 (Ω) =: 1.12 × VO
To reset the actuated protection circuit, either the power supply turn off and on again or set the CTL terminal
(pin 6) to the "L" level to lower the VREF terminal (pin 8) voltage to 1.7 V (Min) or less. It can also be reset by
setting both of the CTL1 terminal (pin 9) and CTL2 terminal (pin 10) to the "L" level.
VO
(−INE2)
R1
15
1
−INE1
R2
Error
− Amp
+
1.23 V
OVP
+ ^Comp.
−
1.38 V
10 µA
CSCP
11
CTL
CTL1
CTL2
SR
Latch
Latch2
VREF
UVLO
PWRGOOD
12
<Timer-latch overvoltage protection circuit>
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