Fujitsu Power Supply MB3878 User Manual

FUJITSU SEMICONDUCTOR  
DATA SHEET  
DS04-27706-2E  
ASSP For Power Supply Applications (Secondary battery)  
DC/DC Converter IC for Charging  
MB3878  
DESCRIPTION  
The MB3878 is a DC/DC converter IC suitable for down-conversion, using pulse-width (PWM) charging and  
enabling output voltage to be set to any desired level from one cell to four cells.  
These ICs can dynamically control the secondary battery’s charge current by detecting a voltage drop in an AC  
adaptor in order to keep its power constant (dynamically-controlled charging).  
The charging method enables quick charging, for example, with the AC adaptor during operation of a notebook PC  
The MB3878 provides a broad power supply voltage range and low standby current as well as high efficiency,  
making it ideal for use as a built-in charging device in products such as notebook PC.  
This product is covered by US Patent Number 6,147,477.  
FEATURES  
• Detecting a voltage drop in the AC adaptor and dynamically controlling the charge current  
(Dynamically-controlled charging)  
• Output voltage setting using external resistor : 1 cell to 4 cells  
• High efficiency  
: 94 %  
• Wide range of operating supply voltages : 7 V to 25 V  
• Output voltage setting accuracy : 4.2V ± 0.8% (per cell)  
• Built-in frequency setting capacitor enables frequency setting using external resistor only  
• Oscillator frequency range : 100kHz to 500kHz  
(Continued)  
PACKAGE  
24-pin plastic SSOP  
(FPT-24P-M03)  
 
MB3878  
PIN DESCRIPTION  
Pin No.  
Symbol  
INC2  
OUTC2  
+INE2  
INE2  
FB2  
I/O  
I
Descriptions  
1
2
Current detection amplifier (Current Amp. 2) input pin.  
Current detection amplifier (Current Amp. 2) output pin.  
Error amplifier (Error Amp. 2) non-inverted input pin.  
Error amplifier (Error Amp. 2) inverted input pin.  
Error amplifier (Error Amp. 2) output pin.  
O
I
3
4
I
5
O
O
O
I
6
VREF  
FB1  
Reference voltage output pin.  
7
Error amplifier (Error Amp. 1) output pin.  
8
INE1  
+INE1  
OUTC1  
Error amplifier (Error Amp. 1) inverted input pin  
Error amplifier (Error Amp. 3) non-inverted input pin.  
Current detection amplifier (Current Amp. 1) output pin.  
9
I
10  
O
With IC in standby mode, this pin is left open to prevent loss of current  
through output voltage setting resistance. Set CTL pin to “H” level and  
OUTD pin to “L” level.  
11  
OUTD  
O
12  
13  
INC1  
+INC1  
I
I
Current detector amplifier (Current Amp. 1) input pin.  
Current detector amplifier (Current Amp. 1) input pin.  
Power supply control pin.  
Setting the CTL pin low places the IC in the standby mode.  
14  
CTL  
I
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
FB3  
INE3  
RT  
O
I
Error amplifier (Error Amp. 3) output pin.  
Error amplifier (Error Amp. 3) inverted input pin.  
Triangular-wave oscillation frequency setting resistor connection pin.  
Power supply pin for reference power supply and control circuit.  
Power supply pin for FET drive circuit (VH = Vcc 5 V).  
High-side FET gate drive pin.  
VCC  
VH  
O
O
OUT  
VCC (O)  
CS  
Output circuit power supply pin.  
Soft-start capacitor connection pin.  
GND  
+INC2  
Ground pin.  
I
Current detection amplifier (Current Amp. 2) input pin.  
3
 
MB3878  
BLOCK DIAGRAM  
8
INE1  
OUTC1  
+INC1  
10  
13  
<Current Amp.1>  
<Error  
Amp.1>  
VREF  
+
× 25  
12  
INC1  
+
21 VCC (O)  
9
7
+INE1  
<PWM Comp.>  
<OUT>  
+
+
+
FB1  
20  
Drive  
OUT  
4
INE2  
2
OUTC2  
<Error  
<Current Amp.2>  
VCC  
VREF  
Amp.2>  
24  
+
× 25  
+INC2  
19  
VH  
Bias  
Voltage  
<VH>  
1
3
INC2  
+INE2  
+
(VCC 5 V)  
FB2 5  
2.5 V  
1.5 V  
<UVLO>  
VCC  
<Error  
Amp.3>  
VREF  
(VCC UVLO)  
215 kΩ  
16  
11  
+
+
INE3  
+
35 kΩ  
OUTD  
4.2 V  
0.91 V  
(0.77 V)  
FB3  
CS  
15  
22  
VREF  
UVLO  
<SOFT>  
VREF  
1 µA  
VCC  
bias  
18  
14  
VCC  
CTL  
<OSC>  
<REF>  
VREF  
<CTL>  
(45 pF)  
5.0 V  
17  
RT  
6
23  
GND  
VREF  
4
 
MB3878  
ABSOLUTE MAXIMUM RAGINGS  
Rating  
Parameter  
Symbol  
Conditions  
VCC, VCC (O)  
Unit  
Min  
Max  
Power supply voltage  
Output current  
VCC  
IOUT  
IOUT  
PD  
28  
60  
V
mA  
mA  
mW  
°C  
Peak output current  
Power dissipation  
Storage temperature  
Duty 5 % (t = 1 / fOSC × Duty)  
Ta +25 °C  
500  
740*  
+125  
Tstg  
55  
* : The package is mounted on the dual-sided epoxy board (10 cm × 10 cm).  
WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current,  
temperature, etc.) in excess of absolute maximum ratings. Do not exceed these ratings.  
RECOMMENDED OPERATING CONDITIONS  
Value  
Symbol  
Parameter  
Conditions  
VCC, VCC (O)  
Unit  
Min  
Typ  
Max  
Power supply voltage  
VCC  
IREF  
7
25  
V
Reference voltage output  
current  
1  
0
mA  
VH pin output current  
IVH  
VINE  
VINC  
VOUTD  
IOUTD  
VCTL  
IOUT  
IOUT  
fOSC  
RT  
0
0
30  
VCC 1.8  
VCC  
17  
mA  
V
INE1 to INE3, +INE1, +INE2  
+INC1, +INC2, INC1, INC2  
Input voltage  
0
V
OUTD pin output voltage  
OUTD pin output current  
CTL pin input voltage  
output current  
0
V
0
2
mA  
V
0
25  
45  
450  
100  
33  
45  
mA  
mA  
kHz  
kΩ  
Peak output current  
Oscillator frequency  
Timing resistor  
Duty 5 % (t = 1 / fosc × Duty)  
450  
500  
130  
290  
47  
Soft-start capacitor  
VH pin capacitor  
CS  
2200  
0.1  
100000 pF  
CVH  
1.0  
1.0  
+85  
µF  
µF  
°C  
Reference voltage output  
capacitor  
CREF  
Ta  
0.1  
Operating ambient temperature  
30  
+25  
WARNING: The recommended operating conditions are required in order to ensure the normal operation of the  
semiconductor device. All of the device’s electrical characteristics are warranted when the device is  
operated within these ranges.  
Always use semiconductor devices within their recommended operating condition ranges. Operation  
outside these ranges may adversely affect reliability and could result in device failure.  
No warranty is made with respect to uses, operating conditions, or combinations not represented on  
the data sheet. Users considering application outside the listed conditions are advised to contact their  
FUJITSU representatives beforehand.  
5
 
MB3878  
ELECTRICAL CHARACTERISTICS  
(Ta = +25 °C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA)  
Value  
Pin  
No.  
Parameter  
Symbol  
Conditions  
Unit  
Min  
Typ  
5.000  
5.000  
3
Max  
5.045  
5.055  
10  
Ta = +25 °C  
4.995  
V
V
Output voltage  
VREF  
6
Ta = 30 °C to +85 °C 4.945  
VCC = 7 V to 25 V  
Reference  
voltage block  
(Ref)  
Input stability  
Load stability  
Line  
6
6
mV  
mV  
Load  
VREF = 0 mA to 1 mA  
1
10  
Short-circuit  
output current  
Ios  
VTLH  
VTHL  
6
VREF = 1 V  
25  
6.1  
5.1  
15  
6.4  
5.4  
5  
6.7  
5.7  
mA  
V
VCC = VCC (O) ,  
VCC =  
18  
18  
Threshold voltage  
VCC = VCC (O) ,  
VCC =  
V
Under voltage  
lockout protection  
circuit block  
(UVLO)  
Hysteresis width  
Threshold voltage  
VH  
VTLH  
VTHL  
VH  
18 VCC = VCC (O)  
0.7  
2.6  
1.0  
2.8  
1.3  
3.0  
V
V
V
V
6
6
6
VREF =  
VREF =  
2.4  
2.6  
2.8  
Hysteresis width  
Charge current  
VH = VTLH VTHL  
0.05  
0.20  
0.35  
Soft-start block  
(SOFT)  
ICS  
22  
1.3  
0.8  
0.5  
µA  
Oscillation  
frequency  
fOSC  
20 RT = 47 kΩ  
260  
290  
320  
kHz  
Triangular  
waveform  
oscillator circuit  
block (OSC)  
Frequency  
temperature  
stability  
f/fdt  
20 Ta = 30 °C to +85 °C  
1*  
%
Input offset  
voltage  
3,4,  
8, 9  
VIO  
IB  
FB1 = FB2 = 2 V  
1
5
mV  
nA  
3,4,  
8, 9  
Input bias current  
100  
30  
Common mode  
input voltage  
range  
3,4,  
8, 9  
VCC −  
1.8  
VCM  
0
V
Error amplifier  
block  
(Error Amp.1,  
Error Amp.2)  
Voltage gain  
AV  
5, 7 DC  
100*  
2.0*  
dB  
Frequency  
bandwidth  
BW  
5, 7 AV = 0 dB  
MHz  
VFBH  
VFBL  
5, 7  
5, 7  
4.7  
4.9  
20  
V
Output voltage  
200  
mV  
Output source  
current  
ISOURCE 5, 7 FB1 = FB2 = 2 V  
ISINK 5, 7 FB1 = FB2 = 2 V  
2.0  
0.6  
mA  
Output sink  
current  
150  
300  
µA  
* : Standard design value.  
(Continued)  
6
 
MB3878  
(Ta = +25 °C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA)  
Value  
Pin  
No.  
Parameter  
Symbol  
Conditions  
Unit  
Min  
Typ  
Max  
VTH1  
16 FB3 = 2 V, Ta = +25 °C 4.167  
FB3 = 2 V,  
4.200  
4.233  
V
V
Threshold voltage  
VTH2  
16  
4.158  
4.200  
4.242  
Ta = 30 °C to +85 °C  
Input current  
Voltage gain  
IINE3  
AV  
16 INE3 = 0 V  
100  
30  
nA  
dB  
15 DC  
100*  
Frequency  
bandwidth  
BW  
15 AV = 0 dB  
2.0*  
MHz  
Error amplifier  
block  
(Error Amp.3)  
VFBH  
15  
15  
4.7  
4.9  
20  
V
Output voltage  
VFBL  
200  
mV  
Output source  
current  
ISOURCE  
15 FB3 = 2 V  
2.0  
300  
0
0.6  
mA  
µA  
µA  
Output sink current  
ISINK  
15 FB3 = 2 V  
150  
OUTD pin output  
leak current  
ILEAK  
11 OUTD = 16.8 V  
1
OUTD pin output  
ON resistor  
RON  
I+INCH  
11 OUTD = 1 mA  
70  
10  
100  
20  
µA  
µA  
µA  
µA  
V
+INC1 = +INC2 = 12.7 V,  
INC1 = INC2 = 12.6 V  
13,  
24  
+INC1 = +INC2 = 12.7 V,  
INC1 = INC2 = 12.6 V  
1,  
12  
IINCH  
0.1  
0.2  
Input current  
+INC1 = +INC2 = 0.1 V,  
INC1 = INC2 = 0 V  
13,  
24  
I+INCL  
130  
140  
2.25  
65  
70  
2.5  
+INC1 = +INC2 = 0.1 V,  
INC1 = INC2 = 0 V  
1,  
12  
IINCL  
+INC1 = +INC2 = 12.7 V,  
INC1 = INC2 = 12.6 V  
2,  
10  
VOUTC1  
VOUTC2  
VOUTC3  
VOUTC4  
2.75  
1.00  
Current  
detection  
amplifier block  
(Current Amp.1,  
Current Amp.2)  
+INC1 = +INC2 = 12.63 V,  
INC1 = INC2 = 12.6 V  
2,  
10  
0.50  
0.75  
2.50  
0.750  
V
Current detection  
voltage  
+INC1 = +INC2 = 0.1 V,  
INC1 = INC2 = 0 V  
2,  
10  
1.25  
3.75  
V
+INC1 = +INC2 = 0.03 V,  
INC1 = INC2 = 0 V  
2,  
10  
0.125  
1.375  
V
1,  
Common mode  
input voltage  
range  
12,  
13,  
24  
VCM  
0
Vcc  
V
2,  
10  
+INC1 = +INC2 = 12.7 V,  
INC1 = INC2 = 12.6 V  
Voltage gain  
AV  
22.5  
25  
27.5  
V/V  
Frequency  
bandwidth  
2,  
10  
BW  
AV = 0 dB  
2.0*  
MHz  
* : Standard design value.  
(Continued)  
7
 
MB3878  
(Continued)  
(Ta = +25 °C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA)  
Value  
Pin  
No.  
Parameter  
Symbol  
Conditions  
Unit  
Min  
Typ  
4.9  
20  
Max  
VOUTCH 2, 10  
4.7  
V
Output voltage  
VOUTCL 2, 10  
200  
mV  
Current detection  
amplifier block  
(Current Amp.1,  
Current Amp.2)  
Output source  
current  
ISOURCE 2, 10 OUTC1 = OUTC2 = 2 V  
2.0  
300  
0.6  
mA  
µA  
V
Output sink  
current  
ISINK  
VTL  
2, 10 OUTC1 = OUTC2 = 2 V  
150  
1.4  
5, 7,  
Duty cycle = 0 %  
1.5  
PWM comparator  
block  
(PWM Comp.)  
15  
Threshold voltage  
5, 7,  
15  
VTH  
Duty cycle = 100 %  
2.5  
2.6  
V
Output source  
current  
OUT = 11 V, Duty 5 %  
20  
ISOURCE  
ISINK  
200*  
200*  
mA  
mA  
(t = 1 / fOSC × Duty)  
Output sink  
current  
OUT = 16 V, Duty 5 %  
20  
(t = 1 / fOSC × Duty)  
ROH  
20 OUT = 45 mA  
20 OUT = 45 mA  
8.0  
6.5  
12.0  
9.7  
Output block  
(OUT)  
Output ON  
resistor  
ROL  
OUT = 3300 pF  
20  
Rise time  
Fall time  
tr1  
tf1  
70*  
60*  
ns  
ns  
(equivalent to Si4435 × 1)  
OUT = 3300 pF  
20  
(equivalent to Si4435 × 1)  
VON  
VOFF  
ICTLH  
ICTLL  
14 Active mode  
14 Standby mode  
14 CTL = 5 V  
2
0
25  
0.8  
200  
1
V
V
CTL input voltage  
Input current  
Control block  
(CTL)  
100  
0
µA  
µA  
14 CTL = 0 V  
VCC = VCC (O)  
19 = 7 V to 25 V,  
VH = 0 to 30 mA  
Bias voltage  
block (VH)  
VCC −  
5.5  
VCC −  
VCC −  
Output voltage  
Standby current  
VH  
V
5.0  
4.5  
18, VCC = VCC (O) ,  
19 CTL = 0 V  
ICCS  
ICC  
0
10  
µA  
General  
Power supply  
current  
18, VCC = VCC (O) ,  
19 CTL = 5 V  
8.0  
12.0  
mA  
* : Standard design value  
8
 
MB3878  
TYPICAL CHARACTERISTICS  
Power supply current vs. power supply voltage  
Reference voltage vs. power supply voltage  
12  
10  
Ta = +25 °C  
CTL = 5 V  
Ta = +25 °C  
CTL = 5 V  
10  
VREF = 0 mA  
8
8
6
4
2
0
6
4
2
0
0
5
10  
15  
20  
25  
0
5
10  
15  
20  
25  
Power supply voltage VCC (V)  
Power supply voltage VCC (V)  
Reference voltage vs. VREF load current  
Reference voltage vs. ambient temperature  
2.0  
10  
VCC = 19 V  
Ta = +25 °C  
VCC = 19 V  
CTL = 5 V  
1.5  
VREF = 0 mA  
CTL = 5 V  
8
1.0  
0.5  
0.0  
6
4
2
0
0.5  
1.0  
1.5  
2.0  
40 20  
0
20  
40  
60  
80  
100  
0
5
10  
15  
20  
25  
30  
VREF load current IREF (mA)  
Ambient temperature Ta ( °C)  
Reference voltage vs. CTL pin voltage  
CTL pin current vs. CTL pin voltage  
1.0  
0.8  
0.6  
0.4  
0.2  
0.0  
10  
8
Ta = +25 °C  
VCC = 19 V  
Ta = +25 °C  
VCC = 19 V  
VREF = 0 mA  
6
4
2
0
0
5
10  
15  
20  
25  
0
0.5  
1
1.5  
2
2.5  
CTL pin voltage VCTL (V)  
CTL pin voltage VCTL (V)  
(Continued)  
9
 
MB3878  
Triangular wave oscillator frequency vs.  
Triangular wave oscillator frequency vs.  
power supply voltage  
timing resistor  
340  
1 M  
100 k  
10 k  
Ta = +25 °C  
VCC = 19 V  
CTL = 5 V  
Ta = +25 °C  
CTL = 5 V  
330  
320  
310  
300  
290  
280  
270  
260  
250  
240  
RT = 47 kΩ  
0
5
10  
15  
20  
25  
10 k  
100 k  
1 M  
Timing resistor RT ()  
Power supply voltage VCC (V)  
Error amplifier threshold voltage vs.  
ambient temperature (Error Amp.3)  
Triangular wave oscillator frequency  
5.0  
4.0  
340  
330  
320  
310  
300  
290  
280  
270  
260  
250  
240  
VCC = 19 V  
CTL = 5 V  
VCC = 19 V  
CTL = 5 V  
RT = 47 kΩ  
3.0  
2.0  
1.0  
0.0  
1.0  
2.0  
3.0  
4.0  
5.0  
40 20  
0
20  
40  
60  
80  
100  
40 20  
0
20  
40  
60  
80  
100  
Ambient temperature Ta ( °C)  
Ambient temperature Ta ( °C)  
(Continued)  
10  
 
MB3878  
(Continued)  
Error amplifier gain and phase vs. frequency  
Ta = +25 °C  
40  
20  
AV  
180  
90  
VCC = 19 V  
240 kΩ  
5.2 V  
10 kΩ  
φ
1 µF  
IN  
2.4 kΩ  
+
8
(4)  
+
OUT  
0
0
7
(5)  
9
10 kΩ  
20  
40  
90  
180  
(3)  
2.5 V  
Error Amp.1  
(Error Amp.2)  
1 k  
10 k  
100 k  
1 M  
10 M  
Frequency f (Hz)  
Current detection amplifier gain and phase  
vs. frequency  
Ta = +25 °C  
φ
40  
180  
VCC = 19 V  
20  
AV  
90  
13  
(24)  
+
×25  
OUT  
0
0
10  
(2)  
12  
(1)  
12.55 V  
20  
40  
90  
180  
Current Amp.1  
(Current Amp.2)  
12.6 V  
1 k  
10 k  
100 k  
1 M  
10 M  
Frequency f (Hz)  
Power dissipation vs. ambient temperature  
800  
740  
700  
600  
500  
400  
300  
200  
100  
0
40 20  
0
20  
40  
60  
80  
100  
Ambient temperature Ta ( °C)  
11  
 
MB3878  
FUNCTIONAL DESCRIPTION  
1. DC/DC Converter Unit  
(1) Reference voltage block (Ref)  
The reference voltage generator uses the voltage supplied from the VCC terminal (pin 18) to generate a tem-  
perature-compensated, stable voltage (5.0V Typ) used as the reference supply voltage for the IC’s internal  
circuitry.  
This pin can also be used to obtain a load current to a maximum of 1mA from the reference voltage VREF  
terminal (pin 6).  
(2) Triangular wave oscillator block (OSC)  
The triangular wave oscillator builds the capacitor for frequency setting into, and generates the triangular wave  
oscillator waveform by connecting the frequency setting resistor with the RT terminal (pin 17).  
The triangular wave is input to the PWM comparator on the IC.  
(3) Error amplifier block (Error Amp.1)  
This amplifier detects the output signal from the current detector ampifier (Current amp .1), compares this to the  
+INE1 terminal (pin 9), and outputs a PWM control signal to be used in controlling the charging current.  
In addition, an arbitrary loop gain can be set up by connecting a feedback resistor and capacitor between the  
FB1 terminal (pin 7) and -INE terminal (pin 8), providing stable phase compensation to the system.  
(4) Error amplifier block (Error Amp.2)  
This amplifier (Error Amp.2) detects voltage pendency of the AC adaptor and outputs a PWM control signal.  
In addition, an arbitrary loop gain can be set by connecting a feedback resistor and capacitor from the FB2  
terminal (pin 5) to the -INE2 terminal (pin 4) of the error amplifier, enabling stable phase compensation to the  
system.  
(5) Error amplifier block (Error Amp.3)  
This error amplifier (Error Amp. 3) detects the output voltage from the DC/DC converter and outputs the PWM  
control signal. External output voltage setting resistors can be connected to the error amplifier inverse input pin  
to set the desired level of output voltage from 1 cell to 4 cells.  
In addition, an arbitrary loop gain can be set by connecting a feedback resistor and capacitor from the FB3  
terminal (pin 15) to the INE3 terminal (pin 16) of the error amplifier, enabling stable phase compensation to the  
system.  
Connecting a soft-start capacitor to the CS terminal (pin 22) prevents surge currents when the IC is turned on.  
Using an error amplifier for soft-start detection makes the soft-start time constant, independent of the output load.  
(6) Current detector amplifier block (Current Amp.1)  
The current detection amplifier (Current Amp.1) detects a voltage drop which occurs between both ends of the  
output sense resistor (RS) due to the flow of the charge current, using the +INC1 terminal (pin 13) and  
INC1 terminal (pin 12). Then it outputs the signal amplified by 25 times to the error amplifier (Error Amp.1) at  
the next stage.  
12  
 
MB3878  
(7) PWM comparator block (PWM Comp.)  
The PWM comparator circuit is a voltage-pulse width converter for controlling the output duty of the error  
amplifiers (Error Amp. 1 to Error Amp. 3) depending on their output voltage.  
The PWM comparator circuit compares the triangular wave generated by the triangular wave oscillator to the  
error amplifier output voltage and turns on the external output transistor during the interval in which the triangular  
wave voltage is lower than the error amplifier output voltage.  
(8) Output block (OUT)  
The output circuit uses a totem-pole configuration capable of driving an external P-channel MOS FET.  
The output “L” level sets the output amplitude to 5 V (Typ) using the voltage generated by the bias voltage block  
(VH).  
This results in increasing conversion efficiency and suppressing the withstand voltage of the connected external  
transistor in a wide range of input voltages.  
(9) Control block (CTL)  
Setting the CTL terminal (pin 14) low places the IC in the standby mode. (The supply current is 10 µA at maximum  
in the standby mode.)  
(10) Bias voltage block (VH)  
The bias voltage circuit outputs Vcc 5 V (Typ) as the minimum potential of the output circuit. In the standby  
mode, this circuit outputs the potential equal to Vcc.  
2. Protection Functions  
Under voltage lockout protection circuit (UVLO)  
The transient state or a momentary decrease in supply voltage or internal reference voltage (VREF), which  
occurs when the power supply is turned on, may cause malfunctions in the control IC, resulting in breakdown  
or degradation of the system. To prevent such malfunction, the under voltage lockout protection circuit detects  
a supply voltage or internal reference voltage drop and fixes the OUT terminal (pin 20) to the “H” level. The  
system restores voltage supply when the supply voltage or internal reference voltage reaches the threshold  
voltage of the under voltage lockout protection circuit.  
3. Soft-start Function  
Soft-start block (SOFT)  
Connecting a capacitor to the CS terminal (pin 22) prevents surge currents when the IC is turned on. Using an  
error amplifier for soft-start detection makes the soft-start time constant, independent of the output load of the  
DC/DC converter.  
13  
 
MB3878  
SETTING THE CHARGING VOLTAGE  
The charging voltage (DC/DC output voltage) can be set by connecting external voltage setting resistors (R3,  
R4) to the -INE3 terminal. Be sure to select a resistor value that allows you to ignore the on resistor (70 , 1mA)  
of the internal FET connected to the OUTD terminal (pin 11).  
Battery charging voltage: VO  
VO (V) = (R3 + R4) / R4 × 4.2 (V)  
VO  
B
R3  
R4  
< Error Amp.3 >  
INE3  
16  
11  
+
+
4.2 V  
OUTD  
22  
CS  
METHOD OF SETTING THE CHARGING CURRENT  
The charge current (output control current) value can be set with the voltage at the +INE1 terminal (pin 9).  
If a current exceeding the set value attempts to flow, the charge voltage drops according to the set current value.  
Battery charge current setting voltage : +INE1  
+INE1 (V) = 25 × I1 (A) × RS ()  
METHOD OF SETTING THE SOFT-START TIME  
Upon activation, the IC starts charging the capacitor (Cs) connected to the CS terminal (pin 22).  
The error amplifier causes soft-start operation to be performed with the output voltage in proportion to the CS  
terminal 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 × CS (µF)  
METHOD OF SETTING THE TRIANGULAR WAVE OSCILLATOR FREQUENCY  
The trianguar wave oscillator frequency can be set by the timing resistor (RT)connected the RTterminal (pin 17).  
Triangular wave oscillator frequency: fOSC  
fOSC (kHz) =: 13630 / RT (k)  
14  
 
MB3878  
AC ADAPTOR VOLTAGE DETECTION  
With an external resistor connected to the +INE2 terminal(pin 3), the IC enters the dynamically-controlled  
charging mode to reduce the charge current to keep AC adaptor power constant when the partial potential point  
A of the AC adaptor voltage (Vcc) becomes lower than the voltage at the -INE2 terminal.  
AC adaptor detected voltage setting: Vth  
Vth (V) = (R1 + R2) / R2 × INE2  
INE2 setting voltage range : 1.176 V to 4.2 V (equivalent to 7 V to 25 V for Vcc)  
<Error Amp.2>  
INE2  
4
3
+
A
VCC  
+INE2  
R1  
R2  
OPERATION TIMING DIAGRAM  
2.5 V  
1.5 V  
Error Amp.1 FB1  
Error Amp.3 FB3  
Error Amp.2 FB2  
OUT  
AC adaptor dynamically-  
controlled charging  
Constant current control  
Constant  
voltage control  
AC adaptor dynamically-  
controlled charging  
15  
 
MB3878  
PROCESSING WITHOUT USE OF THE CS PIN  
If the soft-start function is not used, the CS terminal (pin 22) should be left open.  
Open  
22  
CS  
When no soft-start time is specified.  
NOTE ON AN EXTERNAL REVERSE-CURRENT PREVENTIVE DIODE  
• Insert a reverse-current preventive diode at one of the three locations marked * to prevent reverse current from  
the battery.  
• When selecting the reverse current prevention diode, be sure to consider the reverse voltage (VR) and reverse  
current (IR) of the diode.  
VIN  
VCC(O)  
21  
A
B
OUT  
20  
19  
I1  
BATT  
RS  
VH  
Battery  
16  
 
MB3878  
APPLICATION EXAMPLE 1  
17  
 
MB3878  
PARTS LIST (for APPLICATION EXAMPLE 1)  
COMPONENT  
ITEM  
SPECIFICATION  
VENDOR  
PARTS No.  
VISHAY  
SILICONIX  
VISHAY  
Q1  
Q2  
FET  
FET  
Si4435DY  
2N7002  
Si4435DY  
2N7002  
SILICONIX  
D1  
L1  
Diode  
Coil  
MBRS130LT3  
MOTOROLA  
SUMIDA  
MBRS130LT3  
12 µH  
4.0 A, 38 mΩ  
CDRH124-12 µH  
C1  
C2, C3  
CS  
C5  
C6  
C7  
C8  
C9  
C10  
OS Condenser  
OS Condenser  
22 µF  
100 µF  
2200 pF  
0.1 µF  
25 V (10 %)  
25 V (10 %)  
10 %  
Ceramics Condenser  
Ceramics Condenser  
Ceramics Condenser  
Ceramics Condenser  
Ceramics Condenser  
Ceramics Condenser  
Ceramics Condenser  
16 V  
1500 pF  
0.1 µF  
10 %  
25 V  
10 %  
16 V  
10000 pF  
0.1 µF  
5600 pF  
10 %  
RS  
RT  
R3  
R4  
R5  
R6  
R7  
R8  
R9  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
0.033 Ω  
47 kΩ  
1.0 %  
1.0 %  
1.0 %  
0.5 %  
0.5 %  
0.5 %  
1.0 %  
1.0 %  
1.0 %  
0.5 %  
0.5 %  
0.5 %  
5 %  
330 kΩ  
82 kΩ  
330 kΩ  
68 kΩ  
22 kΩ  
100 kΩ  
10 kΩ  
30 kΩ  
1.3 kΩ  
110 Ω  
200 kΩ  
100 kΩ  
200 kΩ  
R10 to R13  
R14  
R15  
R16  
R17  
R18  
0.5 %  
0.5 %  
Note VISHAY SILICONIX : VISHAY Intertechnology, Inc.  
MOTOROLA : Motorola Japan Ltd.  
SUMIDA : SUMIDA ELECTRIC CO., Ltd.  
18  
 
MB3878  
REFERENCE DATA  
Conversion efficiency vs. charge current  
(Fixed voltage mode)  
Conversion efficiency vs. charge voltage  
(Fixed current mode)  
100  
98  
96  
94  
92  
90  
88  
86  
84  
82  
80  
100  
98  
96  
94  
92  
90  
88  
86  
84  
82  
80  
VIN = 19 V  
VIN = 19 V  
BATT : Electronic load,  
(Product of KIKUSUI PLZ-150W)  
BATT charge voltage = 12.6 V fOSC = 277.9 kHz  
η (%) = (VBATT × IBATT) / (VIN × IIN) × 100  
10 m  
100 m  
1
10  
0
2
4
6
8
10  
12  
14  
16  
BATT charge current IBATT (A)  
BATT charge voltage VBATT (V)  
BATT voltage vs. BATT charge current  
18  
16  
14  
12  
10  
8
VIN = 19 V  
BATT : Electronic load,  
(Product of KIKUSUI PLZ-150W)  
DCC MODE  
Dead Battery MODE  
6
4
2
DCC : Dynamically Controlled Charging  
5
0
0
1
2
3
4
BATT charge current IBATT (A)  
DC/DC converter switching waveforms  
Soft-start operating waveforms  
VIN = 19 V  
VIN = 19 V  
fOSC = 277.9 kHz  
Load : BATT = 1 A  
Load : BATT = 20 Ω  
INE2 = 0 V  
OUTH (V)  
20  
BATT (V)  
20  
5 V  
5 V  
15  
10  
5
15  
10  
CTL (V)  
20  
5
0
0
15  
10  
5
FB3 (V)  
4
2
0
0
2 V  
2
1 µs  
5 V  
40  
20 ms  
0
4
6
8
10  
0
80  
120  
160  
200  
t (µs)  
t (ms)  
19  
 
MB3878  
APPLICATION EXAMPLE 2  
20  
 
MB3878  
PARTS LIST (for APPLICATION EXAMPLE 2)  
COMPONENT  
ITEM  
SPECIFICATION  
VENDOR  
PARTS No.  
Q1  
Q2  
FET  
FET  
Si4435DY  
2N7002  
VISHAY SILICONIX  
VISHAY SILICONIX  
Si4435DY  
2N7002  
D1  
A
Diode  
MBRS130LT3  
MB47358  
MOTOROLA  
Our Company  
MBRS130LT3  
MB47358  
Dual Op-amp  
4.0 A,  
12 µH  
L1  
Coil  
SUMIDA  
CDRH124-12 µH  
38 mΩ  
C1  
C2, C3  
CS  
C5  
C6  
C7  
C8  
C9  
C10  
OS Condenser  
OS Condenser  
Ceramics Condenser 2200 pF  
Ceramics Condenser  
Ceramics Condenser 1500 pF  
Ceramics Condenser 0.1 µF  
Ceramics Condenser 10000 pF  
Ceramics Condenser 0.1 µF  
Ceramics Condenser 5600 pF  
22 µF  
25 V (10 %)  
25 V (10 %)  
10 %  
100 µF  
0.1 µF  
16 V  
10 %  
25 V  
10 %  
16 V  
10 %  
RS1, RS2  
RT  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
Resistor  
0.033 Ω  
47 kΩ  
1.0 %  
1.0 %  
1.0 %  
1.0 %  
1.0 %  
1.0 %  
0.5 %  
0.5 %  
0.5 %  
0.5 %  
0.5 %  
5 %  
1.0 %  
0.5 %  
1.0 %  
0.5 %  
1.0 %  
R3  
R7  
R8  
R9  
330 kΩ  
22 kΩ  
100 kΩ  
10 kΩ  
R10  
R11  
R12, R13  
R14  
36 kΩ  
27 kΩ  
30 kΩ  
1.3 kΩ  
110 Ω  
R15  
R16  
R17  
R18  
200 kΩ  
100 kΩ  
200 kΩ  
100 kΩ  
100 kΩ  
100 kΩ  
R19, R20  
R21, R22  
R23  
Note VISHAY SILICONIX : VISHAY Intertechnology, Inc.  
MOTOROLA : Motorola Japan Ltd.  
SUMIDA : SUMIDA ELECTRIC CO., Ltd.  
21  
 
MB3878  
USAGE PRECAUTIONS  
• Printed circuit board ground lines should be set up with consideration for common impedance.  
Take appropriate static electricity measures.  
• Containers for semiconductor materials should have anti-static protection or be made of conductive material.  
• After mounting, printed circuit boards should be stored and shipped in conductive bags or containers.  
• Work platforms, tools, and instruments should be properly grounded.  
• Working personnel should be grounded with resistance of 250 kto 1 Mbetween body and ground.  
• Do not apply negative voltages.  
The use of negative voltages below –0.3 V may create parasitic transistors on LSI lines, which can cause  
abnormal operation  
ORDERING INFORMATION  
Part number  
MB3878PFV  
Package  
Remarks  
24-pin plastic SSOP  
(FPT-24P-M03)  
22  
 
MB3878  
PACKAGE DIMENSION  
24-pin plastic SSOP  
(FPT-24P-M03)  
Note1: Pins width and pins thickness include plating thickness.  
Note2: * This dimension does not include resin protrusion.  
0.17±0.03  
(.007±.001)  
*
7.75±0.10(.305±.004)  
24  
13  
5.60±0.10 7.60±0.20  
(.220±.004) (.299±.008)  
INDEX  
Details of "A" part  
1.25 +0.20  
–0.10  
–.004  
(Mounting height)  
.049 +.008  
0.25(.010)  
0~8°  
"A"  
1
12  
0.24 +0.08  
.009 +.003  
–0.07  
0.65(.026)  
M
0.13(.005)  
–.003  
0.50±0.20  
0.10±0.10  
(.020±.008)  
(.004±.004)  
(Stand off)  
0.60±0.15  
(.024±.006)  
0.10(.004)  
C
2001 FUJITSU LIMITED F24018S-c-3-4  
Dimensions in mm (inches)  
23  
 
MB3878  
FUJITSU LIMITED  
All Rights Reserved.  
The contents of this document are subject to change without notice.  
Customers are advised to consult with FUJITSU sales  
representatives before ordering.  
The information and circuit diagrams in this document are  
presented as examples of semiconductor device applications, and  
are not intended to be incorporated in devices for actual use. Also,  
FUJITSU is unable to assume responsibility for infringement of  
any patent rights or other rights of third parties arising from the use  
of this information or circuit diagrams.  
The products described in this document are designed, developed  
and manufactured as contemplated for general use, including  
without limitation, ordinary industrial use, general office use,  
personal use, and household use, but are not designed, developed  
and manufactured as contemplated (1) for use accompanying fatal  
risks or dangers that, unless extremely high safety is secured, could  
have a serious effect to the public, and could lead directly to death,  
personal injury, severe physical damage or other loss (i.e., nuclear  
reaction control in nuclear facility, aircraft flight control, air traffic  
control, mass transport control, medical life support system, missile  
launch control in weapon system), or (2) for use requiring  
extremely high reliability (i.e., submersible repeater and artificial  
satellite).  
Please note that Fujitsu will not be liable against you and/or any  
third party for any claims or damages arising in connection with  
above-mentioned uses of the products.  
Any semiconductor devices have an inherent chance of failure. You  
must protect against injury, damage or loss from such failures by  
incorporating safety design measures into your facility and  
equipment such as redundancy, fire protection, and prevention of  
over-current levels and other abnormal operating conditions.  
If any products described in this document represent goods or  
technologies subject to certain restrictions on export under the  
Foreign Exchange and Foreign Trade Law of Japan, the prior  
authorization by Japanese government will be required for export  
of those products from Japan.  
F0209  
FUJITSU LIMITED Printed in Japan  
 

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