MB3813A Datasheet, PDF (16/22 Pages) Fujitsu Component Limited. – Lithium Ion Battery Charger DC/DC Converter IC (High Precision with Constant-current Function)

MB3813A/MB3833A/MB3843
s METHOD OF SETTING THE CHARGING CURRENT
The charging current level (output limit current level) is set at the Vin2 pin (pin 8).
Charging current level (output limit current level) :
IL (MAX) [A] =
Vin2 (V)
25 × RS (Ω)
RS: output sensing resistance
s METHOD OF SETTING THE SOFT START TIME
• At start up, the capacitor (Cs) connected to the CS pin (pin 11) begins charging. The error amplifier compares
the soft start setting voltage, which is proportional to the CS pin voltage, to the output feedback voltage and
produces a soft start by varying the ON duty at the OUT pin (pin 15). The soft start time can be determined
by the formula below.
• Because the CS pin voltage is input to the error amplifier, the soft start time setting is not dependent on the
output current value.
Soft start time (time to output setting voltage VD) :
ts [s] = 2.5 × CS [µF]
s ERROR AMP. BLOCK OVERSHOOT PROTECTION CIRCUIT
This built-in circuit responds to rapid fluctuations in charging current such as can occur when inserting or removing
a chargeable battery, by clamping an inverted input signal (-IN1 or -IN2) from the error amps (Error Amp.1 or
Error Amp.2) to suppress changes in output voltage.
s CTL, SEL PIN EQUIVALENT CIRCUITS
CTL
7
VCC
SEL
10
1.4 V
16