Fujitsu MB3878 User's Manual

Fujitsu MB3878 User's 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
(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)
24 : +INC2
−INC2 : 1
23 : GND
OUTC2 : 2
+INE2 : 3
22 : CS
−INE2 : 4
21 : VCC (O)
20 : OUT
FB2 : 5
19 : VH
VREF : 6
18 : VCC
FB1 : 7
−INE1 : 8
17 : RT
+INE1 : 9
16 : −INE3
OUTC1 : 10
15 : FB3
OUTD : 11
14 : CTL
−INC1 : 12
13 : +INC1
(FPT-24P-M03)
2
MB3878
■ 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.
3
MB3878
■ BLOCK DIAGRAM
−INE1 8
OUTC1 10
<Current Amp.1>
+
× 25
−
−INC1 12
+INC1 13
<Error
Amp.1> VREF
−
+
21 VCC (O)
+INE1 9
<PWM Comp.>
<OUT>
+
+
+
Drive
−
FB1 7
−INE2 4
OUTC2 2
+INC2 24
−INC2 1
<Current Amp.2>
+
× 25
−
+INE2 3
<Error
Amp.2> VREF
−
20 OUT
VCC
19 VH
(VCC − 5 V)
Bias
Voltage
<VH>
+
FB2 5
2.5 V
1.5 V
<UVLO>
<Error
Amp.3> VREF
(VCC UVLO) 215 kΩ
+
−
+
+
−INE3 16
OUTD 11
−
4.2 V
FB3 15
VCC
35 kΩ
0.91 V
(0.77 V)
VREF
UVLO
<SOFT>
VREF
1 µA
VCC
bias
CS 22
<OSC>
(45 pF)
17
RT
4
<REF>
18 VCC
<CTL>
VREF
5.0 V
6
23
GND
VREF
14 CTL
MB3878
■ ABSOLUTE MAXIMUM RAGINGS
Parameter
Symbol
Conditions
Rating
Unit
Min
Max

28
V

60
mA
Power supply voltage
VCC
Output current
IOUT
Peak output current
IOUT
Duty ≤ 5 % (t = 1 / fOSC × Duty)

500
mA
Power dissipation
PD
Ta ≤ +25 °C

740*
mW
−55
+125
°C
Storage temperature
VCC, VCC (O)


Tstg
* : 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
Parameter
Symbol
Conditions
Value
Unit
Min
Typ
Max
7

25
V
Power supply voltage
VCC
Reference voltage output
current
IREF

−1

0
mA
VH pin output current
IVH

0

30
mA
Input voltage
VCC, VCC (O)
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

2
mA
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
Ta

−30
+25
+85
°C
Operating ambient temperature
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
Parameter
Reference
voltage block
(Ref)
(Ta = +25 °C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA)
Value
Pin
Symbol
Conditions
Unit
No.
Min
Typ
Max
Ta = +25 °C
4.995
5.000
5.045
V
Ta = −30 °C to +85 °C
4.945
5.000
5.055
V
VCC = 7 V to 25 V

3
10
mV
6
VREF = 0 mA to −1 mA

1
10
mV
Ios
6
VREF = 1 V
−25
−15
−5
mA
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
VH
18
VCC = VCC (O)
0.7
1.0
1.3
V
VTLH
6
VREF =
2.6
2.8
3.0
V
VTHL
6
VREF =
2.4
2.6
2.8
V
Hysteresis width
VH
6
VH = VTLH − VTHL
0.05
0.20
0.35
V
Charge current
ICS
22
−1.3
−0.8
−0.5
µA
Oscillation
frequency
fOSC
20
RT = 47 kΩ
260
290
320
kHz
Frequency
temperature
stability
∆f/fdt
20
Ta = −30 °C to +85 °C

1*

%
Input offset
voltage
VIO

1
5
mV
Output voltage
VREF
6
Input stability
Line
6
Load stability
Load
Short-circuit
output current
Threshold voltage
Under voltage
lockout protection
Hysteresis width
circuit block
(UVLO)
Threshold voltage
Soft-start block
(SOFT)
Triangular
waveform
oscillator circuit
block (OSC)
3, 4,
FB1 = FB2 = 2 V
8, 9
IB
3, 4,
8, 9

−100
−30

nA
Common mode
input voltage
range
VCM
3, 4,
8, 9

0

VCC −
1.8
V
Voltage gain
AV
5, 7 DC

100*

dB
Frequency
bandwidth
BW
5, 7 AV = 0 dB

2.0*

MHz
VFBH
5, 7

4.7
4.9

V
VFBL
5, 7


20
200
mV
Input bias current
Error amplifier
block
(Error Amp.1,
Error Amp.2)

Output voltage
Output source
current
Output sink
current
ISOURCE
5, 7 FB1 = FB2 = 2 V

−2.0
−0.6
mA
ISINK
5, 7 FB1 = FB2 = 2 V
150
300

µA
* : Standard design value.
(Continued)
6
MB3878
Parameter
16
VTH2
16
Input current
IINE3
16
FB3 = 2 V,
Ta = −30 °C to +85 °C
−INE3 = 0 V
Voltage gain
AV
15
Frequency
bandwidth
BW
15
VFBH
15
VFBL
15
ISOURCE
15
ISINK
Output voltage
Output source
current
Output sink current
OUTD pin output
leak current
OUTD pin output
ON resistor
4.167
4.200
4.233
V
4.158
4.200
4.242
V
−100
−30

nA
DC

100*

dB
AV = 0 dB

2.0*

MHz

4.7
4.9

V


20
200
mV
FB3 = 2 V

−2.0
−0.6
mA
15
FB3 = 2 V
150
300

µA
ILEAK
11
OUTD = 16.8 V

0
1
µA
RON
11
OUTD = 1 mA

70
100
Ω
I+INCH
13,
24
1,
12
13,
24
1,
12
2,
10
2,
10
2,
10
2,
10
1,
12,
13,
24
+INC1 = +INC2 = 12.7 V,
−INC1 = −INC2 = 12.6 V

10
20
µA
+INC1 = +INC2 = 12.7 V,
−INC1 = −INC2 = 12.6 V

0.1
0.2
µA
+INC1 = +INC2 = 0.1 V,
−INC1 = −INC2 = 0 V
−130
−65

µA
+INC1 = +INC2 = 0.1 V,
−INC1 = −INC2 = 0 V
−140
−70

µA
+INC1 = +INC2 = 12.7 V,
−INC1 = −INC2 = 12.6 V
2.25
2.5
2.75
V
+INC1 = +INC2 = 12.63 V,
−INC1 = −INC2 = 12.6 V
0.50
0.75
1.00
V
+INC1 = +INC2 = 0.1 V,
−INC1 = −INC2 = 0 V
1.25
2.50
3.75
V
+INC1 = +INC2 = 0.03 V,
−INC1 = −INC2 = 0 V
0.125
0.750
1.375
V

0

Vcc
V
22.5
25
27.5
V/V

2.0*

MHz
I−INCH
Input current
I+INCL
I−INCL
VOUTC1
Current
detection
amplifier block
(Current Amp.1,
Current Amp.2)
FB3 = 2 V, Ta = +25 °C
VTH1
Threshold voltage
Error amplifier
block
(Error Amp.3)
(Ta = +25 °C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA)
Value
Pin
Symbol
Conditions
Unit
No.
Min
Typ
Max
Current detection
voltage
VOUTC2
VOUTC3
VOUTC4
Common mode
input voltage
range
VCM
Voltage gain
AV
2,
10
+INC1 = +INC2 = 12.7 V,
−INC1 = −INC2 = 12.6 V
Frequency
bandwidth
BW
2,
10
AV = 0 dB
* : Standard design value.
(Continued)
7
MB3878
(Continued)
Parameter
Output voltage
Current detection
amplifier block
Output source
(Current Amp.1, current
Current Amp.2)
Output sink
current
PWM comparator
block
Threshold voltage
(PWM Comp.)
4.9

V
VOUTCL 2, 10


20
200
mV
ISOURCE
2, 10 OUTC1 = OUTC2 = 2 V

−2.0
−0.6
mA
ISINK
2, 10 OUTC1 = OUTC2 = 2 V
150
300

µA
VTL
5, 7,
Duty cycle = 0 %
15
1.4
1.5

V
VTH
5, 7,
Duty cycle = 100 %
15

2.5
2.6
V

−200*

mA
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
(equivalent to Si4435 × 1)

70*

ns
Fall time
tf1
20

60*

ns
VON
14
Active mode
2

25
V
VOFF
14
Standby mode
0

0.8
V
ICTLH
14
CTL = 5 V

100
200
µA
ICTLL
14
CTL = 0 V

0
1
µA
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
Standby current
ICCS
18,
19
VCC = VCC (O) ,
CTL = 0 V

0
10
µA
Power supply
current
ICC
18,
19
VCC = VCC (O) ,
CTL = 5 V

8.0
12.0
mA
Control block
(CTL)
Input current
* : Standard design value
8
4.7
OUT = 11 V, Duty ≤ 5 %
(t = 1 / fOSC × Duty)
CTL input voltage
General

20
Output sink
current
Bias voltage
block (VH)
2, 10
VOUTCH
ISOURCE
Output source
current
Output block
(OUT)
(Ta = +25 °C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA)
Value
Pin
Symbol
Conditions
Unit
No.
Min
Typ
Max
OUT = 3300 pF
OUT = 3300 pF
(equivalent to Si4435 × 1)
MB3878
■ TYPICAL CHARACTERISTICS
Power supply current vs. power supply voltage
Reference voltage vs. power supply voltage
10
Ta = +25 °C
CTL = 5 V
10
Reference voltage VREF (V)
Power supply current
ICC (mA)
12
8
6
4
2
0
0
5
10
15
20
Ta = +25 °C
CTL = 5 V
VREF = 0 mA
8
6
4
2
0
25
0
5
Power supply voltage VCC (V)
Reference voltage vs. VREF load current
2.0
Ta = +25 °C
VCC = 19 V
CTL = 5 V
8
6
4
2
5
10
15
20
25
0.5
0.0
−0.5
−1.0
−1.5
30
0
20
40
60
80
100
Ta = +25 °C
VCC = 19 V
VREF = 0 mA
6
4
2
CTL pin current vs. CTL pin voltage
1.0
CTL pin current ICTL (mA)
Reference voltage VREF (V)
−20
Ambient temperature Ta ( °C)
Reference voltage vs. CTL pin voltage
8
25
1.0
VREF load current IREF (mA)
10
20
VCC = 19 V
CTL = 5 V
VREF = 0 mA
1.5
−2.0
−40
0
0
15
Reference voltage vs. ambient temperature
Reference voltage ∆VREF (%)
Reference voltage VREF (V)
10
10
Power supply voltage VCC (V)
Ta = +25 °C
VCC = 19 V
0.8
0.6
0.4
0.2
0.0
0
0
0.5
1
1.5
2
CTL pin voltage VCTL (V)
2.5
0
5
10
15
20
25
CTL pin voltage VCTL (V)
(Continued)
9
Triangular wave oscillator frequency vs.
timing resistor
1M
Ta = +25 °C
VCC = 19 V
CTL = 5 V
100 k
10 k
10 k
100 k
1M
Triangular wave oscillator frequency
fOSC (kHz)
Triangular wave oscillator frequency
fOSC (Hz)
MB3878
Triangular wave oscillator frequency vs.
power supply voltage
340
Ta = +25 °C
CTL = 5 V
RT = 47 kΩ
330
320
310
300
290
280
270
260
250
240
0
Timing resistor RT (Ω)
Triangular wave oscillator
frequency fOSC (kHz)
320
310
300
290
280
270
260
250
240
−40
−20
0
20
40
60
80
Ambient temperature Ta ( °C)
100
Error amplifier threshold voltage ∆VTH (%)
VCC = 19 V
CTL = 5 V
RT = 47 kΩ
330
10
15
20
25
Power supply voltage VCC (V)
Error amplifier threshold voltage vs.
ambient temperature (Error Amp.3)
Triangular wave oscillator frequency
340
5
5.0
VCC = 19 V
CTL = 5 V
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
Ambient temperature Ta ( °C)
(Continued)
10
MB3878
(Continued)
Error amplifier gain and phase vs. frequency
40
Ta = +25 °C
AV
180
VCC = 19 V
φ
20
90
0
0
240 kΩ
Phase φ (deg)
Gain AV (dB)
5.2 V
−20
−90
−40
−180
1k
10 k
100 k
1M
IN
1 µF
− +
10 kΩ
2.4 kΩ
10 kΩ
8
(4)
−
OUT
7
(5)
9 +
(3)
2.5 V Error Amp.1
(Error Amp.2)
10 M
Frequency f (Hz)
Current detection amplifier gain and phase
vs. frequency
180
90
AV
0
0
−20
−90
VCC = 19 V
Phase φ (deg)
20
Gain AV (dB)
Ta = +25 °C
φ
40
12.6 V
−40
13 +
OUT
(24) ×25
10
(2)
12 −
(1)
12.55 V Current Amp.1
(Current Amp.2)
−180
1k
10 k
100 k
1M
10 M
Frequency f (Hz)
Power dissipation PD (mW)
Power dissipation vs. ambient temperature
800
740
700
600
500
400
300
200
100
0
−40
−20
0
20
40
60
80
Ambient temperature Ta ( °C)
100
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 temperature-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 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)
B VO
R3
< Error Amp.3 >
−INE3
16
R4
11
OUTD
−
+
+
4.2 V
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 (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 RT terminal (pin 17).
Triangular wave oscillator frequency: fOSC
fOSC (kHz) =: 13630 / RT (kΩ)
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
R1
+INE2
R2
■ OPERATION TIMING DIAGRAM
2.5 V
Error Amp.1 FB1
Error Amp.3 FB3
Error Amp.2 FB2
1.5 V
OUT
AC adaptor dynamically- Constant
controlled charging
voltage control
Constant current control
AC adaptor dynamicallycontrolled 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
CS 22
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.
21
VCC(O)
VIN
∗
A
20
B
OUT
∗
I1
RS
∗
VH
19
16
Battery
BATT
SW
R16
R15
200 kΩ 110 Ω
Q2
R14
1.3 kΩ
R6
68 kΩ
R5
330 kΩ
R4
82 kΩ
8
FB2 5
CS
2200 pF
15
CS 22
FB3
R18
200 kΩ −INE3
16
R17
C6
100 kΩ
1500 pF
11
R3
OUTD
330 kΩ
R7
22 kΩ
+INE2 3
<SOFT>
VREF
1 µA
C8
4
10000 pF
OUTC2
R10
2
<Current Amp.2>
30 kΩ
+INC2 24
+
R11
× 25
30 kΩ
−INC2 1
−
−INE2
OUTC1 10
<Current Amp.1>
C10 5600 pF
+INC1
+
A
13
R9
× 25
10 kΩ
−
B −INC1 12
R12
30 kΩ
+INE1 9
R13
FB1
30 kΩ
7
R8
100 kΩ −INE1
4.2 V
RT
RT
47 kΩ
(45 pF)
VCC
2.5 V
1.5 V
VREF
UVLO
VREF
6
<CTL>
VCC
C9
0.1 µF
VREF
5.0 V
23
GND
<REF>
bias
35 kΩ
0.91 V
(0.77 V)
−
VCC (O)
20
14
18
C2
100 µF
L1
12 µH
+
−
C1
22 µF
A
B
+ Battery
−
C3
100 µF
BATT
AC Adaptor
RS
0.033 Ω
I1
VIN
C7
0.1 µF
Output voltage (Battery voltage) is adjustable
D1
Q1
+
−
IIN
Note : SW ON : DCC MODE
SW OFF : Dead Battery MODE
Range of input voltage
VIN=13V to 21V(at Load = 3A)
CTL
VCC
VH
OUT
C5
0.1 µF
21
19
(VCC − 5 V)
(VCC UVLO) 215 kΩ
+
<UVLO>
Bias
Voltage
<VH>
VCC
<PWM Comp.>
<OUT>
+
+
+
Drive
−
17
<OSC>
<Error
Amp.3> VREF
−
+
+
+
<Error
Amp.2> VREF
−
+
<Error
Amp.1> VREF
−
MB3878
■ APPLICATION EXAMPLE 1
17
MB3878
■ PARTS LIST (for APPLICATION EXAMPLE 1)
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 mΩ
SUMIDA
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 %


Note
18
VISHAY SILICONIX : VISHAY Intertechnology, Inc.
MOTOROLA : Motorola Japan Ltd.
SUMIDA : SUMIDA ELECTRIC CO., Ltd.
MB3878
■ REFERENCE DATA
Conversion efficiency vs. charge current
(Fixed voltage mode)
VIN = 19 V
BATT charge voltage = 12.6 V fOSC = 277.9 kHz
η (%) = (VBATT × IBATT) / (VIN × IIN) × 100
98
96
94
92
90
88
86
84
82
80
10 m
100 m
1
10
100
Conversion efficiency η (%)
Conversion efficiency η (%)
100
Conversion efficiency vs. charge voltage
(Fixed current mode)
VIN = 19 V
BATT : Electronic load,
(Product of KIKUSUI PLZ-150W)
98
96
94
92
90
88
86
84
82
80
0
2
BATT charge current IBATT (A)
4
6
8
10
12
14
16
BATT charge voltage VBATT (V)
BATT voltage vs. BATT charge current
BATT voltage
VBATT (V)
18
VIN = 19 V
BATT : Electronic load,
(Product of KIKUSUI PLZ-150W)
16
14
12
10
DCC MODE
Dead Battery MODE
8
6
4
2
DCC : Dynamically Controlled Charging
0
0
1
2
3
BATT charge current
4
5
IBATT (A)
DC/DC converter switching waveforms
Soft-start operating waveforms
VIN = 19 V
Load : BATT = 20 Ω
−INE2 = 0 V
BATT (V)
20
OUTH (V)
20
5V
15
5V
15
CTL (V) 10
5
20
10
0
0
15
VIN = 19 V
fOSC = 277.9 kHz
Load : BATT = 1 A
5
10
FB3 (V)
4
5
2
0
5V
0
40
20 ms
80
120
160
200
t (ms)
1 µs
2V
0
0
2
4
6
8
10
t (µs)
19
20
R21
100 kΩ
R22
100 kΩ
−
−
R20
100 kΩ
VIN
+ A(2/2)
Q2
R19
100 kΩ
+ A(1/2)
VIN
SW
R16
200 kΩ
R15
110 Ω
CS
2200 pF
C6
1500 pF
R3
330 kΩ
R18
200 kΩ
D
R7
22 kΩ
R10
24 kΩ
R11
36 kΩ
C
R23
100 kΩ
B
A
C8
10000 pF
R13
30 kΩ
C10
5600 pF
R9
10 kΩ
R14
R12
1.3 kΩ 30 kΩ
8
15
CS 22
FB3
−INE3
16
R17
100 kΩ
11
OUTD
FB2 5
+INC2 24
<SOFT>
VREF
1 µA
<Current Amp.2>
+
× 25
−INC2 1
−
+INE2
3
4
7
9
13
OUTC2 2
−INE2
FB1
+INE1
+INC1
<Current Amp.1>
+
× 25
−INC1
−
12
OUTC1 10
R8
100 kΩ −INE1
4.2 V
RT
RT
47 kΩ
(45 pF)
VCC
2.5 V
1.5 V
VREF
UVLO
VREF
6
<CTL>
VCC
C9
0.1 µF
VREF
5.0 V
23
GND
<REF>
bias
35 kΩ
0.91 V
(0.77 V)
−
VCC (O)
20
CTL
VCC
C2
100 µF
L1
12 µH
+
−
C1
22 µF
B
+ Battery
−
C3
100 µF
RS1
0.033 Ω
A
RS2
0.033 Ω
D
BATT
System
C7
0.1 µF
Output voltage (Battery voltage) is adjustable
D1
Q1
+
−
C
Note : SW ON : Differential Charging MODE
SW OFF : Dead Battery MODE
Range of input voltage
VIN = 13V to 21V(at Load = 3A)
14
18
VH
OUT
C5
0.1 µF
21
19
(VCC − 5 V)
(VCC UVLO) 215 kΩ
+
<UVLO>
Bias
Voltage
<VH>
VCC
<PWM Comp.>
<OUT>
+
+
+
Drive
−
17
<OSC>
<Error
Amp.3> VREF
−
+
+
+
<Error
Amp.2> VREF
−
+
<Error
Amp.1> VREF
−
VIN
AC Adaptor
MB3878
■ APPLICATION EXAMPLE 2
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
Diode
MBRS130LT3
MOTOROLA
MBRS130LT3
A
Dual Op-amp
MB47358
Our Company
MB47358
L1
Coil
12 µH
4.0 A,
38 mΩ
SUMIDA
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 %


RS1, RS2
RT
R3
R7
R8
R9
R10
R11
R12, R13
R14
R15
R16
R17
R18
R19, R20
R21, R22
R23
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
Resistor
0.033 Ω
47 kΩ
330 kΩ
22 kΩ
100 kΩ
10 kΩ
36 kΩ
27 kΩ
30 kΩ
1.3 kΩ
110 Ω
200 kΩ
100 kΩ
200 kΩ
100 kΩ
100 kΩ
100 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 %


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 kΩ to 1 MΩ between 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
22
Package
24-pin plastic SSOP
(FPT-24P-M03)
Remarks
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
+0.20
1.25 –0.10
+.008
.049 –.004
(Mounting height)
0.25(.010)
1
"A"
12
0~8°
+0.08
0.65(.026)
0.24 –0.07
+.003
.009 –.003
0.13(.005)
M
0.50±0.20
(.020±.008)
0.60±0.15
(.024±.006)
0.10±0.10
(.004±.004)
(Stand off)
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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