FUJITSU SEMICONDUCTOR
DATA SHEET
DS04-27704-2E
ASSP
For Power Supply Applications (Lithium ion battery charger)
DC/DC Converter IC for Parallel Charging
MB3874/MB3876
s
DESCRIPTION
The MB3874 and MB3876 are parallel charging DC/DC converter ICs suitable for down-conversion, which uses
pulse width modulation (PWM) for controlling the output voltage and current independently.
These ICs can dynamically control the secondary battery’s charge current by detecting a voltage drop in an AC
adapter in order to keep its power constant (dynamically-controlled charging).
The charging method enables quick charging, for example, with the AC adapter during operation of a notebook PC.
The IC also enable parallel charging, or charging two batteries at the same time, dramatically reducing the charging
time.
With an on-chip output voltage setting resistor which allows the output voltage to be set at high precision, these
ICs are best suited as internal battery chargers for notebook PCs.
The MB3874 support 3-cell battery and the MB3876 support 4-cell battery.
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FEATURES
• Detecting a voltage drop in the AC adapter and dynamically controlling the charge current (Dynamically-con-
trolled charging)
• High efficiency
: 93 %(In reverse-current preventive diode)
• Wide range of operating supply voltages
: 7 V to 25 V
• Output voltage precision
(Built-in output voltage setting resistor )
:
±
0.8 % (Ta =
+
25
°C)
• High precision reference voltage source
: 4.2 V
±
0.8 %
(Continued)
s
PACKAGE
24-pin plastic SSOP
(FPT-24P-M03)
MB3874/MB3876
(Continued)
• Support for frequency setting using an external resistor
(Frequency setting capacitor integrated)
:100 kHz to 500 kHz
• Built-in current detector amplifier with wide in-phase input voltage range
: 0 V to V
CC
• Built-in standby current function
: 0
µA
(Typ.)
• Built-in soft start function
• Capable of parallel charging (Charging the two battery packs at a time)
• Internal totem-pole output stage supporting P-channel MOS FETs devices
2
MB3874/MB3876
s
PIN DESCRIPTION
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Symbol
–INC1
FB2
–INE2
+INE2
VREF
CTL
FB1
–INE1
+INE3
–INE3
FB3
–INC2
+INC2
–INE5
FB4
–INE4
RT
OUTM
VH
OUT
V
CC
CS
GND
+INC1
I/O
I
O
I
I
O
I
O
I
I
I
O
I
I
I
O
I
—
O
O
O
—
—
—
I
Descriptions
Output voltage feedback input pin.
Error amplifier (Error Amp. 2) output pin.
Error amplifier (Error Amp. 2) inverted input pin.
Error amplifier (Error Amp. 2) non-inverted input pin.
Input pin for charge current setting voltage
Reference voltage output pin.
Power supply control pin.
Setting the CTL pin low places the IC in the standby mode.
Error amplifier (Error Amp. 1) output pin.
Error amplifier (Error Amp. 1) inverted input pin
Input pin for dynamically-controlled charging voltage setting
Error amplifier (Error Amp. 3) non-inverted input pin.
Input pin for charge current setting voltage
Error amplifier (Error Amp. 3) inverted input pin.
Error amplifier (Error Amp. 3) output pin.
Output voltage feedback input pin.
Current detection amplifier (Current Amp. 2) input pin .
Error amplifier (Error Amp. 5) inverted input pin.
Error amplifier (Error Amp. 4, 5) output pin.
Error amplifier (Error Amp. 4) inverted input pin.
Triangular-wave oscillation frequency setting resistor connection pin.
Output pin for dynamically controlled charging identification signal
“H” level: Constant-voltage or constant-current charging mode
“L” level: Dynamically controlled charging mode
Power supply pin for FET drive circuit (VH = Vcc
−
5 V).
High-side FET gate drive pin.
Power supply pin for reference power supply and control circuit.
Soft-start capacitor connection pin.
Ground pin.
Current detection amplifier (Current Amp. 1) input pin .
4
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