MB3874 Fujitsu Media Devices, MB3874 Datasheet - Page 17

• Manufacturer Part Number: MB3874
• Description: DC/DC Converter IC for Parallel Charging
• Manufacturer: Fujitsu Media Devices

METHOD OF SETTING THE CHARGING CURRENT
The charge current (output control current) value can be set with the voltage at the +INE2, +INE3 terminal.
If a current exceeding the set value attempts to flow, the charge voltage drops according to the set current value.
Battery 1 charge current setting voltage : +INE2
+INE2 (V) = 25
Battery 2 charge current setting voltage : +INE3
+INE3 (V) = 25
METHOD OF SETTING THE SOFT START TIME
Upon activation, the IC starts charging the capacitor (Cs) connected to the CS terminal .
The error amplifier causes soft start operation to be performed with the output voltage in proportion to the CS
pin voltage regardless of the load current of the DC/DC converter.
Soft start time ts (Time taken for the output voltage to reach 100 %)
ts (s) : = 4.2
METHOD OF SETTING THE TRIANGULAR WAVE OSCILLATOR FREQUENCY SETTING
The trianguar wave oscillator frequency can be set by the timing resistor (R
Triangular wave oscillator frequency f
f
AC ADAPTER VOLTAGE DETECTION
pin, the IC enters the constant-power mode to reduce the charge current in order to keep AC adapter power
constant.
AC adapter detected voltage setting Vth
Vth (V) = (208k + 42k) / 42k
OSC
When partial potential point A of the AC adapter voltage (Vcc) becomes lower than the voltage at the –INE1
INE1 setting voltage range : 1.176 V to 4.2 V (equivalent to 7 V to 25 V for Vcc)
(kHz) : = 14444 / R
C
S
( F)
I1 (A)
I2 (A)
T
(k )
R
R
S
S
1 ( )
2 ( )
INE1
INE1 : = 5.95
8
OSC
V
CC
208 k
INE1
A
42 k
<Error Amp.1>
MB3874/MB3876
T
) connected the RT terminal (pin 17).
17