Fujitsu MB3878 User manual

DS04-27706-2E
FUJITSU SEMICONDUCTOR
DATA SHEET
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).
Thechargingmethodenablesquickcharging,forexample,withtheAC adaptor duringoperationofanotebookPC
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
2
(Continued)
• Built-in current detector amplifier with wide in-phase input voltage range : 0 V to Vcc
• In standby mode, leave output voltage setting resistor open to prevent inefficient current loss
• Built-in standby current function : 0 µA (standard)
• Built-in soft-start function
• Built-in totem-pole output stage supporting P-channel MOS FETs devices
■
■■
■PIN ASSIGNMENT
(TOP VIEW)
(FPT-24P-M03)
1
2
3
4
5
6
7
8
9
10
11
12
−INC2 :
OUTC2 :
+INE2 :
−INE2 :
FB2 :
VREF :
FB1 :
−INE1 :
+INE1 :
OUTC1 :
OUTD :
−INC1 :
24
23
22
21
20
19
18
17
16
15
14
13
: +INC2
: GND
: CS
: VCC (O)
: OUT
: VH
: VCC
: RT
: −INE3
: FB3
: CTL
: +INC1

MB3878
3
■
■■
■PIN DESCRIPTION
Pin No. Symbol I/O Descriptions
1−INC2 I Current detection amplifier (Current Amp. 2) input pin.
2 OUTC2 O Current detection amplifier (Current Amp. 2) output pin.
3+INE2 I Error amplifier (Error Amp. 2) non-inverted input pin.
4−INE2 I Error amplifier (Error Amp. 2) inverted input pin.
5 FB2 O Error amplifier (Error Amp. 2) output pin.
6 VREF O Reference voltage output pin.
7 FB1 O Error amplifier (Error Amp. 1) output pin.
8−INE1 I Error amplifier (Error Amp. 1) inverted input pin
9+INE1 I Error amplifier (Error Amp. 3) non-inverted input pin.
10 OUTC1 O Current detection amplifier (Current Amp. 1) output pin.
11 OUTD 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.
12 −INC1 I Current detector amplifier (Current Amp. 1) input pin.
13 +INC1 I Current detector amplifier (Current Amp. 1) input pin.
14 CTL I Power supply control pin.
Setting the CTL pin low places the IC in the standby mode.
15 FB3 O Error amplifier (Error Amp. 3) output pin.
16 −INE3 I Error amplifier (Error Amp. 3) inverted input pin.
17 RT Triangular-wave oscillation frequency setting resistor connection pin.
18 VCC Power supply pin for reference power supply and control circuit.
19 VH O Power supply pin for FET drive circuit (VH = Vcc −5 V).
20 OUT O High-side FET gate drive pin.
21 VCC (O) Output circuit power supply pin.
22 CS Soft-start capacitor connection pin.
23 GND Ground pin.
24 +INC2 I Current detection amplifier (Current Amp. 2) input pin.

MB3878
4
■
■■
■BLOCK DIAGRAM
+
−−
+
8
10
13
12
9
+
−−
+
4
2
24
1
3
×25
×25
+
+
+
−
5
20
21
19
−
+
+
+
−
11
16
22
17 6 23
14
18
<Current Amp.1> <Error
Amp.1>
7
VREF
<Current Amp.2> <Error
Amp.2> VREF
<Error
Amp.3> VREF
VREF
VREF
5.0 V
4.2 V
1 µA
15 <SOFT>
2.5 V
1.5 V
<OUT>
<UVLO>
<OSC>
Bias
Voltage
<VH>
<REF> <CTL>
<PWM Comp.>
Drive
VCC
(VCC −5 V)
(VCC UVLO)
VCC
VCC
VCC
CTL
215 kΩ
35 kΩ
0.91 V
(0.77 V)
VREF
UVLO
bias
−INC2
OUTD
FB2
OUTC2
VREF
−INE2
+INE2
+INE1
FB1
OUTC1
−INE1
−INC1
+INC2
GND
CS
VCC (O)
OUT
VH
RT
−INE3
FB3
+INC1
(45 pF)

MB3878
5
■
■■
■ABSOLUTE MAXIMUM RAGINGS
* : 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
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.
Parameter Symbol Conditions Rating Unit
Min Max
Power supply voltage VCC VCC, VCC (O) 28 V
Output current IOUT 60 mA
Peak output current IOUT Duty ≤5 %(t =1 /fOSC ×Duty) 500 mA
Power dissipation PDTa ≤+25 °C740* mW
Storage temperature Tstg −55 +125 °C
Parameter Symbol Conditions Value Unit
Min Typ Max
Power supply voltage VCC VCC, VCC (O) 7 25 V
Reference voltage output
current IREF −10mA
VH pin output current IVH 030 mA
Input voltage VINE −INE1 to −INE3, +INE1, +INE2 0 VCC −1.8 V
VINC +INC1, +INC2, −INC1, −INC2 0 VCC V
OUTD pin output voltage VOUTD 017 V
OUTD pin output current IOUTD 02mA
CTL pin input voltage VCTL 025 V
output current IOUT −45 45 mA
Peak output current IOUT Duty ≤5 %(t =1 /fosc ×Duty) −450 450 mA
Oscillator frequency fOSC 100 290 500 kHz
Timing resistor RT33 47 130 kΩ
Soft-start capacitor CS2200 100000 pF
VH pin capacitor CVH 0.1 1.0 µF
Reference voltage output
capacitor CREF 0.1 1.0 µF
Operating ambient temperature Ta −30 +25 +85 °C

MB3878
6
■
■■
■ELECTRICAL CHARACTERISTICS (Ta =+25 °C, VCC =19 V, VCC (O) =19 V, VREF =0 mA)
* : Standard design value.
(Continued)
Parameter Symbol Pin
No. Conditions Value Unit
Min Typ Max
Reference
voltage block
(Ref)
Output voltage VREF 6Ta =+25 °C 4.995 5.000 5.045 V
Ta =−30 °C to +85 °C 4.945 5.000 5.055 V
Input stability Line 6 VCC =7 V to 25 V 310mV
Load stability Load 6 VREF =0 mA to −1 mA 110mV
Short-circuit
output current Ios 6 VREF =1 V −25 −15 −5mA
Under voltage
lockout protection
circuit block
(UVLO)
Threshold voltage VTLH 18 VCC =VCC (O) ,
VCC =6.1 6.4 6.7 V
VTHL 18 VCC =VCC (O) ,
VCC =5.1 5.4 5.7 V
Hysteresis width VH18 VCC =VCC (O) 0.7 1.0 1.3 V
Threshold voltage VTLH 6VREF=2.6 2.8 3.0 V
VTHL 6VREF=2.4 2.6 2.8 V
Hysteresis width VH6VH=VTLH −VTHL 0.05 0.20 0.35 V
Soft-start block
(SOFT) Charge current ICS 22 −1.3 −0.8 −0.5 µA
Triangular
waveform
oscillator circuit
block (OSC)
Oscillation
frequency fOSC 20 RT =47 kΩ260 290 320 kHz
Frequency
temperature
stability ∆f/fdt 20 Ta =−30 °C to +85 °C 1* %
Error amplifier
block
(Error Amp.1,
Error Amp.2)
Input offset
voltage VIO 3,4,
8, 9 FB1 =FB2 =2 V 15mV
Input bias current IB3,4,
8, 9 −100 −30 nA
Common mode
input voltage
range VCM 3,4,
8, 9 0VCC − 1.8 V
Voltage gain AV5, 7 DC 100* dB
Frequency
bandwidth BW5, 7 AV=0 dB 2.0* MHz
Output voltage VFBH 5, 7 4.7 4.9 V
VFBL 5, 7 20 200 mV
Output source
current ISOURCE 5, 7 FB1 =FB2 =2 V −2.0 −0.6 mA
Output sink
current ISINK 5, 7 FB1 =FB2 =2 V 150 300 µA

MB3878
7
(Ta =+25 °C, VCC =19 V, VCC (O) =19 V, VREF =0 mA)
* : Standard design value.
(Continued)
Parameter Symbol Pin
No. Conditions Value Unit
Min Typ Max
Error amplifier
block
(Error Amp.3)
Threshold voltage VTH1 16 FB3 =2 V, Ta =+25 °C 4.167 4.200 4.233 V
VTH2 16 FB3 =2 V,
Ta =−30 °C to +85 °C 4.158 4.200 4.242 V
Input current IINE3 16 −INE3 =0 V −100 −30 nA
Voltage gain AV15 DC 100* dB
Frequency
bandwidth BW15 AV=0 dB 2.0* MHz
Output voltage VFBH 15 4.7 4.9 V
VFBL 15 20 200 mV
Output source
current ISOURCE 15 FB3 =2 V −2.0 −0.6 mA
Output sink current ISINK 15 FB3 =2 V 150 300 µA
OUTD pin output
leak current ILEAK 11 OUTD =16.8 V 01µA
OUTD pin output
ON resistor RON 11 OUTD =1 mA 70 100 Ω
Current
detection
amplifier block
(Current Amp.1,
Current Amp.2)
Input current
I+INCH 13,
24 +INC1 =+INC2 =12.7 V,
−INC1 =−INC2 =12.6 V 10 20 µA
I−INCH 1,
12 +INC1 =+INC2 =12.7 V,
−INC1 =−INC2 =12.6 V 0.1 0.2 µA
I+INCL 13,
24 +INC1 =+INC2 =0.1 V,
−INC1 =−INC2 =0 V −130 −65 µA
I−INCL 1,
12 +INC1 =+INC2 =0.1 V,
−INC1 =−INC2 =0 V −140 −70 µA
Current detection
voltage
VOUTC1 2,
10 +INC1 =+INC2 =12.7 V,
−INC1 =−INC2 =12.6 V 2.25 2.5 2.75 V
VOUTC2 2,
10 +INC1=+INC2=12.63V,
−INC1 =−INC2 =12.6 V 0.50 0.75 1.00 V
VOUTC3 2,
10 +INC1 =+INC2 =0.1 V,
−INC1 =−INC2 =0 V 1.25 2.50 3.75 V
VOUTC4 2,
10 +INC1 =+INC2 =0.03 V,
−INC1 =−INC2 =0 V 0.125 0.750 1.375 V
Common mode
input voltage
range VCM
1,
12,
13,
24
0Vcc V
Voltage gain AV2,
10 +INC1 =+INC2 =12.7 V,
−INC1 =−INC2 =12.6 V 22.5 25 27.5 V/V
Frequency
bandwidth BW2,
10 AV=0 dB 2.0* MHz

MB3878
8
(Continued)
(Ta =+25 °C, VCC =19 V, VCC (O) =19 V, VREF =0 mA)
* : Standard design value
Parameter Symbol Pin
No. Conditions Value Unit
Min Typ Max
Current detection
amplifier block
(Current Amp.1,
Current Amp.2)
Output voltage VOUTCH 2, 10 4.7 4.9 V
VOUTCL 2, 10 20 200 mV
Output source
current ISOURCE 2, 10 OUTC1 =OUTC2 =2 V −2.0 −0.6 mA
Output sink
current ISINK 2, 10 OUTC1 =OUTC2 =2 V 150 300 µA
PWM comparator
block
(PWM Comp.) Threshold voltage VTL 5, 7,
15 Duty cycle =0 %1.4 1.5 V
VTH 5, 7,
15 Duty cycle =100 %2.5 2.6 V
Output block
(OUT)
Output source
current ISOURCE 20 OUT =11 V, Duty ≤5 %
(t =1 /fOSC ×Duty) −200* mA
Output sink
current ISINK 20 OUT =16 V, Duty ≤5 %
(t =1 /fOSC ×Duty) 200* mA
Output ON
resistor ROH 20 OUT =−45 mA 8.0 12.0 Ω
ROL 20 OUT =45 mA 6.5 9.7 Ω
Rise time tr1 20 OUT =3300 pF
(equivalent to Si4435 ×1) 70* ns
Fall time tf1 20 OUT =3300 pF
(equivalent to Si4435 ×1) 60* ns
Control block
(CTL)
CTL input voltage VON 14 Active mode 2 25 V
VOFF 14 Standby mode 0 0.8 V
Input current ICTLH 14 CTL =5 V 100 200 µA
ICTLL 14 CTL =0 V 01µA
Bias voltage
block (VH) Output voltage VH 19 VCC =VCC (O)
=7 V to 25 V,
VH =0 to 30 mA
VCC −
5.5 VCC − 5.0 VCC − 4.5 V
General Standby current ICCS 18,
19 VCC =VCC (O) , CTL =0 V 010µA
Power supply
current ICC 18,
19 VCC =VCC (O) , CTL =5 V 8.0 12.0 mA

MB3878
9
■
■■
■TYPICAL CHARACTERISTICS
(Continued)
Ta =+25 °C
CTL =5 V
12
10
8
6
4
2
00 5 10 15 20 25
Ta =+25 °C
CTL =5 V
VREF =0 mA
10
8
6
4
2
00 5 10 15 20 25
Ta =+25 °C
VCC =19 V
CTL =5 V
10
8
6
4
2
00 5 10 15 20 25 30
2.0
1.5
1.0
0.5
0.0
−0.5
−1.0
−1.5
−2.0
−40 −20 0 20 40 60 80 100
VCC =19 V
CTL =5 V
VREF =0 mA
Ta =+25 °C
VCC =19 V
VREF =0 mA
10
8
6
4
2
00 0.5 1 1.5 2 2.5
Ta =+25 °C
VCC =19 V
1.0
0.8
0.6
0.4
0.2
0.00 5 10 15 20 25
Power supply current
ICC (mA)
Power supply current vs. power supply voltage
Power supply voltage VCC (V)
Reference voltage VREF (V)
Power supply voltage VCC (V)
Reference voltage vs. power supply voltage
Reference voltage VREF (V)
VREF load current IREF (mA)
Reference voltage vs. VREF load current Reference voltage vs. ambient temperature
Referencevoltage∆VREF (%)
Ambient temperature Ta ( °C)
Reference voltage vs. CTL pin voltage
Reference voltage VREF (V)
CTL pin voltage VCTL (V)
CTL pin current vs. CTL pin voltage
CTL pin current ICTL (mA)
CTL pin voltage VCTL (V)

MB3878
10
(Continued)
Ta =+25 °C
VCC =19 V
CTL =5 V
1 M
100 k
10 k
10 k 100 k 1 M
Ta =+25 °C
CTL =5 V
RT =47 kΩ
340
330
320
310
300
290
280
270
260
250
2400 5 10 15 20 25
VCC =19 V
CTL =5 V
RT =47 kΩ
340
330
320
310
300
290
280
270
260
250
240
−40 −20 0 20 40 60 80 100
VCC =19 V
CTL =5 V
5.0
4.0
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
Triangular wave oscillator frequency vs.
timing resistor
Timing resistor RT(Ω)
Triangular wave oscillator frequency vs.
power supply voltage
Power supply voltage VCC (V)
Triangular wave oscillator frequency
Triangular wave oscillator
frequency fOSC (kHz)
Ambient temperature Ta ( °C)
Error amplifier threshold voltage vs.
ambient temperature (Error Amp.3)
Error amplifier threshold voltage ∆VTH (%)
Ambient temperature Ta ( °C)
Triangular wave oscillator frequency
fOSC (Hz)
Triangular wave oscillator frequency
fOSC (kHz)

MB3878
11
(Continued)
−
+
−+
VCC = 19 V
Error Amp.1
(Error Amp.2)
(3) (5)
(4)
2.5 V
10 kΩ
2.4 kΩ
240 kΩ
10 kΩ
5.2 V
1 µF
OUT
IN
φ
AVTa =+25 °C 40
20
0
−20
−40
180
90
0
−90
−180
1 k 10 k 100 k 1 M 10 M
7
8
9
VCC = 19 V
Current Amp.1
(Current Amp.2)
+
−
(1) (2)
(24) ×25
12.55 V12.6 V
OUT
φTa =+25 °C
40
20
0
−20
−40
180
90
0
−90
−180
1 k 10 k 100 k 1 M 10 M
AV
10
13
12
800
740
700
600
500
400
300
200
100
0
−40 −20 0 20 40 60 80 100
Error amplifier gain and phase vs. frequency
Gain AV(dB)
Frequency f (Hz)
Phase φ(deg)
Current detection amplifier gain and phase
vs. frequency
Gain AV(dB)
Frequency f (Hz)
Phase φ(deg)
Power dissipation vs. ambient temperature
Power dissipation PD(mW)
Ambient temperature Ta ( °C)

MB3878
12
■
■■
■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.
Usinganerroramplifierforsoft-startdetectionmakesthesoft-starttimeconstant,independentoftheoutputload.
(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.

MB3878
13
(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
erroramplifieroutput voltageand turnsonthe external output transistorduring the intervalin which thetriangular
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)
SettingtheCTLterminal(pin14)lowplacestheICinthestandbymode. (Thesupplycurrentis10µAatmaximum
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.

MB3878
14
■
■■
■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 Ω, 1mA)
of the internal FET connected to the OUTD terminal (pin 11).
Battery charging voltage: VO
VO(V) =(R3 +R4) /R4 ×4.2 (V)
■
■■
■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(Ω)
■
■■
■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 (kΩ)
< Error Amp.3 >
−
+
+
4.2 V
R3
VO
R4
−INE3
OUTD
CS
16
B
11
22

MB3878
15
■
■■
■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)
■
■■
■OPERATION TIMING DIAGRAM
−
+
VCC R1
R2
+INE2
−INE2
A
<Error Amp.2>
4
3
2.5 V
1.5 V
Error Amp.1
Error Amp.3
Error Amp.2
FB1
FB3
FB2
OUT
Constant
voltage control
AC adaptor dynamically-
controlled charging Constant current control AC adaptor dynamically-
controlled charging

MB3878
16
■
■■
■PROCESSING WITHOUT USE OF THE CS PIN
If the soft-start function is not used, the CS terminal (pin 22) should be left open.
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.
22
CS
Open
VCC(O)
OUT
VIN
VH
I1 RSBATT
Battery
A B
∗
∗
∗
21
20
19

MB3878
17
■
■■
■APPLICATION EXAMPLE 1
+
−−
+
8
10
13
12
A
B
9
+
−−
+
4 2
24
1 3
×25 ×25
+ + +
−
5
20 21 19
−
+ +
+
−
11
16 22
17 6 23
14 18
<Current Amp.1> <Error
Amp.1>
7
VREF
<Current Amp.2> <Error
Amp.2> VREF
<Error Amp.3> VREF
VREF
VREF 5.0 V
4.2 V
1 µA
15 <SOFT>
2.5 V 1.5 V
<OUT>
<UVLO>
<OSC>
Bias
Voltage
<VH>
<REF> <CTL>
<PWM Comp.>
Drive
VCC
(V
CC
−5 V)
(VCC UVLO)
VCC
VCC VCC
CTL
215 kΩ
35 kΩ
0.91 V
(0.77 V)
VREF
UVLO
bias
−INC2
OUTD
FB2
VREF
−INE2
+INE2
+INE1
FB1
OUTC1
−INE1
−INC1
+INC2
GND
CS
VCC (O)
OUT Q1
Output voltage (Battery voltage) is adjustable
D1
I1
Battery
VH
RT
−INE3
FB3
+INC1
(45 pF)
R8 100 kΩ
C10 5600 pF
+ −
+ −+
−
R9
10 kΩ
R14
1.3 kΩ
R10
30 kΩ
R11
30 kΩ
R7
22 kΩ
R18
200 kΩR17
100 kΩ
C6
1500 pF
C
S
2200 pF
R3
330 kΩ
R
T
47 kΩC9
0.1 µF
C7 0.1 µF
C5
0.1 µF
C2
100 µFC3
100 µF
C1 22 µF
R
S
0.033 Ω
L1
12 µH
R4
82 kΩ
R5
330 kΩ
R6
68 kΩ
R15
110 Ω
R16
200 kΩ
Q2
SW
Note : SW ON : DCC MODE
R12
30 kΩ
R13
30 kΩ
C8 10000 pF
A B
AC Adaptor
IIN
BATT
OUTC2
SW OFF : Dead Battery MODE Range of input voltage VIN=13V to 21V(at Load = 3A)
VIN

MB3878
18
■
■■
■PARTS LIST (for APPLICATION EXAMPLE 1)
Note VISHAY SILICONIX : VISHAY Intertechnology, Inc.
MOTOROLA : Motorola Japan Ltd.
SUMIDA : SUMIDA ELECTRIC CO., Ltd.
COMPONENT ITEM SPECIFICATION VENDOR PARTS No.
Q1
Q2 FET FET Si4435DY 2N7002
VISHAY
SILICONIX
VISHAY
SILICONIX
Si4435DY
2N7002
D1 Diode MBRS130LT3 MOTOROLA MBRS130LT3
L1 Coil 12 µH 4.0 A, 38 mΩSUMIDA CDRH124-12 µH
C1
C2, C3
CS
C5
C6
C7
C8
C9
C10
OS Condenser
OS Condenser
Ceramics Condenser
Ceramics Condenser
Ceramics Condenser
Ceramics Condenser
Ceramics Condenser
Ceramics Condenser
Ceramics Condenser
22 µF
100 µF
2200 pF
0.1 µF
1500 pF
0.1 µF
10000 pF
0.1 µF
5600 pF
25 V (10 %)
25 V (10 %)
10 %
16 V
10 %
25 V
10 %
16 V
10 %

RS
RT
R3
R4
R5
R6
R7
R8
R9
R10 to R13
R14
R15
R16
R17
R18
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
0.033 Ω
47 kΩ
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
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 %
0.5 %
0.5 %


MB3878
19
■
■■
■REFERENCE DATA
100
98
96
94
92
90
88
86
84
82
80
10 m 100 m 1 10
100
98
96
94
92
90
88
86
84
82
800 2 4 6 8 10 12 14 16
18
16
14
12
10
8
6
4
2
0012345
DCC : Dynamically Controlled Charging
Dead Battery MODE DCC MODE
20
15
10
5
0
20
15
10
5
0
0 80 120 160 200
t (ms)
40
BATT (V)
CTL (V)
5 V
5 V 20 ms
20
15
10
5
0
4
2
0
0468102
OUTH (V)
FB3 (V)
5 V
2 V 1 µs
t (µs)
Conversion efficiency vs. charge current
(Fixed voltage mode) Conversion efficiency vs. charge voltage (Fixed current mode)
Conversion efficiency η(%)
BATT charge current IBATT (A)
Conversion efficiency η(%)
BATT charge voltage VBATT (V)
BATT voltage vs. BATT charge current
VIN =19 V
BATT : Electronic load,
(ProductofKIKUSUIPLZ-150W)
BATT voltage VBATT (V)
BATT charge current IBATT (A)
VIN =19 V
BATT charge voltage =12.6 V fOSC =277.9 kHz
η(%) =(VBATT ×IBATT) /(VIN ×IIN) ×100
Soft-start operating waveforms
VIN =19 V
Load : BATT =20 Ω
−INE2 =0 V
VIN =19 V
fOSC =277.9 kHz
Load : BATT =1 A
DC/DC converter switching waveforms
VIN =19 V
BATT : Electronic load,
(Product of KIKUSUI PLZ-150W)

MB3878
20
■
■■
■APPLICATION EXAMPLE 2
+
−−
+
8
10
13
12
A
B
C
D
9
+
−
+
−
+
−
−
+
4 2
24
1 3
×25 ×25
+ + +
−
5
20 21 19
−
+ +
+
−
11
16 22
17 6 23
14 18
<Current Amp.1> <Error
Amp.1>
7
VREF
<Current Amp.2> <Error
Amp.2> VREF
<Error Amp.3> VREF
VREF
VREF 5.0 V
4.2 V
1 µA
15 <SOFT>
2.5 V 1.5 V
<OUT>
<UVLO>
<OSC>
Bias
Voltage
<VH>
<REF> <CTL>
<PWM Comp.>
Drive
V
CC
(V
CC
−5 V)
(VCC UVLO)
VCC
VCC VCC
CTL
215 kΩ
35 kΩ
0.91 V
(0.77 V)
VREF
UVLO
bias
−INC2
OUTD
FB2
VREF
−INE2
+INE2
+INE1
FB1
OUTC1
−INE1
−INC1
+INC2
GND
CS
VCC (O)
OUT Q1
Output voltage (Battery voltage) is adjustable
D1 Battery
VH
RT
−INE3
FB3
+INC1
(45 pF)
R8 100 kΩ
C10
5600 pF
+ −
+ −+
−
R9
10 kΩ
R14 1.3 kΩ
R10
24 kΩ
R11
36 kΩ
R7
22 kΩ
R18
200 kΩR17
100 kΩ
C
S
2200 pF
R3
330 kΩ
R
T
47 kΩC9
0.1 µF
C7 0.1 µF
C5
0.1 µF
C2
100 µFC3
100 µF
C1 22 µF
R
S
1
0.033 Ω
R
S
2
0.033 Ω
L1
12 µH
R22
100 kΩ
R21
100 kΩ
R19
100 kΩ
R20
100 kΩ
R15
110 Ω
R16
200 kΩQ2
A(1/2) A(2/2)
SW
VIN VIN
Note : SW ON : Differential Charging MODE
R12
30 kΩ
R13
30 kΩ
C8
10000 pF
A B
C D
System
AC Adaptor
VIN
BATT
OUTC2
R23
100 kΩ
C6
1500 pF
SW OFF : Dead Battery MODE Range of input voltage VIN = 13V to 21V(at Load = 3A)