MB39A113 Datasheet, PDF (16/51 Pages) Fujitsu Component Limited. – ASSP for Power Supply Applications (Secondary Battery)

MB39A113
2. Protection Functions
(1) Under-voltage lockout protection circuit (UVLO)
The transient state of when the power supply (VCC) is turned on or a momentary decrease in supply voltage/
internal reference voltage (VREF) may cause malfunctions in the control IC, resulting in breakdown or degra-
dation of the system. To prevent such malfunctions, the under-voltage lockout protection circuit detects an internal
reference voltage drop and fixes OUT terminal (pin 20) to “H” level. The system restores when the internal
reference voltage reaches the threshold voltage of the under-voltage lockout protection circuit.
Protection circuit (UVLO) operation function table
At UVLO operating (VREF voltage is lower than UVLO threshold voltage.)
OUTD
OUT
CS
CVM
Hi-Z
H
L
H
OVP
H
(2) AC adapter detection block (UV Comp.)
This block detects that power-supply voltage (VCC) is lower than the battery voltage + 0.2 V (Typ) , and the OUT
terminal (pin 18) fixed at the “H” level. The system restores voltage supply when the supply voltage reaches the
threshold voltage of the AC adapter detection block.
Protection circuit (UV Comp.) operation function table
At UV Comp. operating (VCC voltage is lower than UV Comp. threshold voltage.)
OUTD
OUT
CS
L
H
L
3. Soft-start Function
Soft-start block (SOFT)
Connecting a capacitor to the CS terminal (pin 22) prevents rush currents from flowing upon activation of the
power supply.
Using the error amplifier to detect a soft-start allows to soft-start at constant setting time intervals independent
of the output load of the DC/DC converter.
4. Detection Function
(1) Constant-voltage control state detection block (CV Comp.)
Error amplifier (Error Amp3) detects the voltage at FB3 (pin 15) falling to or below 2.6 V (Typ) and outputs “L”
level to the constant-voltage control state detection block output terminal (CVM, pin 5).
(2) Overvoltage detection block (OV Comp.)
Error amplifier (Error Amp3) detects the voltage at FB3 (pin 15) falling to or below 1.3 V (Typ) and outputs “H”
level to the overvoltage detection block output terminal (OVP, pin 18).
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