Fujitsu 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 batter y’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, f or example, with the A C 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

PACKAGE

■■■■

24-pin plastic SSOP

(FPT-24P-M03)

(Continued)

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)

: +INC2

−INC2 :

OUTC2 :

+INE2 :

1

2

3

24

23

22

: GND

: CS

−INE2 :

FB2 :

VREF :

FB1 :

−INE1 :

+INE1 :

OUTC1 :

OUTD :

−INC1 :

10

11

12

: VCC (O)

4

5

6

7

8

9

21

20

19

18

17

16

15

14

13

: OUT

: VH

: VCC

: RT

: −INE3

: FB3

: CTL

: +INC1

(FPT-24P-M03)

2

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.

With IC in standby mode, this pin is left open to prevent loss of current

11 OUTD O

12 −INC1 I Current detector amplifier (Current Amp. 1) input pin.

through output voltage setting resistance. Set CTL pin to “H” level and
OUTD pin to “L” level.

MB3878

13 +INC1 I Current detector amplifier (Current Amp. 1) input pin.
14 CTL I
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.

Power supply control pin.
Setting the CTL pin low places the IC in the standby mode.

3

MB3878

BLOCK DIAGRAM

■■■■

−INE1

OUTC1

+INC1

−INC1

+INE1

FB1

−INE2

8

10

<Current Amp.1>

13
12

9
7

4

+
× 25

−

<Error
Amp.1>

−
+

VREF

<PWM Comp.>

+
+
+

−

<OUT>

Drive

21

20

VCC (O)

OUT

OUTC2

+INC2

−INC2
+INE2

FB2

−INE3

OUTD

FB3

CS

2

<Current Amp.2>

24

1
3

5

16

11

15

<SOFT>

VREF

22

+
× 25

−

1 µA

<Error
Amp.2>

−
+

<Error
Amp.3>

−
+
+

4.2 V

VREF

VREF

(45 pF)

(VCC UVLO)

bias

<OSC>

17 6 23
RT

<REF> <CTL>

VREF

VCC

Bias

Voltage

<VH>

<UVLO>

0.91 V

(0.77 V)

VREF
UVLO

VREF

5.0 V

(V

2.5 V

1.5 V

215 kΩ

+

35 kΩ

−

VCC

GND

CC − 5 V)

VCC

19

18
14

VH

VCC
CTL

4

ABSOLUTE MAXIMUM RAGINGS

■■■■

MB3878

Parameter Symbol Conditions

Unit

Min Max

Power supply voltage VCC VCC, VCC (O)  28 V

Rating

Output current I
Peak output current I

OUT 60 mA
OUT Duty ≤ 5 % (t = 1 / fOSC × Duty)  500 mA

Power dissipation PD Ta ≤ +25 °C  740* mW

Storage temperature Tstg −55 +125 °C
* : 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

Parameter

Symbol

Conditions

Min Typ Max

Power supply voltage V

Reference voltage output

current

VH pin output current I

CC VCC, VCC (O) 7  25 V

I

REF −1  0mA

VH  0  30 mA

VINE −INE1 to −INE3, +INE1, +INE2 0  VCC − 1.8 V

Input voltage

V

INC +INC1, +INC2, −INC1, −INC2 0  VCC V

Unit

OUTD pin output voltage V

OUTD pin output current I

OUTD  0  17 V

OUTD  0  2mA

CTL pin input voltage VCTL  0  25 V

output current I

Peak output current I

OUT −45  45 mA
OUT Duty ≤ 5 % (t = 1 / fosc × Duty) −450  450 mA

Oscillator frequency fOSC  100 290 500 kHz

Timing resistor R

Soft-start capacitor C

T  33 47 130 kΩ
S 2200 100000 pF

VH pin capacitor CVH 0.1 1.0 µF

Reference voltage output

capacitor

C

REF 0.1 1.0 µF

Operating ambient temperature Ta −30 +25 +85 °C
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 Symbol

(Ta = +25 °C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA)

Pin
No.

Conditions

Min Typ Max

Value

Unit

Reference

voltage block

(Ref)

Under voltage

lockout protection

circuit block

(UVLO)

Soft-start block

(SOFT)

Triangular

waveform

oscillator circuit

block (OSC)

Output voltage V

REF 6

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

Ta = +25 °C 4.995 5.000 5.045 V

Short-circuit
output current

Ios 6 VREF = 1 V −25 −15 −5mA

TLH 18

V

VCC = VCC (O) ,

VCC =

6.1 6.4 6.7 V

Threshold voltage

V

THL 18

VCC = VCC (O) ,

VCC =

5.1 5.4 5.7 V

Hysteresis width VH 18 VCC = VCC (O) 0.7 1.0 1.3 V

TLH 6VREF = 2.6 2.8 3.0 V

V

Threshold voltage

V

THL 6VREF = 2.4 2.6 2.8 V

Hysteresis width VH 6VH = VTLH − VTHL 0.05 0.20 0.35 V
Charge current I
Oscillation

frequency

CS 22 −1.3 −0.8 −0.5 µA

OSC 20 RT = 47 kΩ 260 290 320 kHz

f

Frequency
temperature

∆f/fdt 20 Ta = −30 °C to +85 °C  1* %

stability
Input offset

voltage

V

3, 4,

IO

FB1 = FB2 = 2 V  15mV

8, 9

Error amplifier
block
(Error Amp.1,
Error Amp.2)

* : Standard design value.

6

Input bias current I
Common mode

input voltage

V

range
Voltage gain A
Frequency

bandwidth

V

Output voltage

VFBL 5, 7 20 200 mV

Output source
current

Output sink
current

I

SOURCE 5, 7 FB1 = FB2 = 2 V −2.0 −0.6 mA

I

3, 4,

B

8, 9

3, 4,

CM

8, 9

V 5, 7 DC  100*  dB

B

W 5, 7 AV = 0 dB  2.0*  MHz

FBH 5, 7  4.7 4.9  V

SINK 5, 7 FB1 = FB2 = 2 V 150 300 µA

−100 −30  nA

 0 

VCC −

1.8

(Continued)

V

Parameter Symbol

TH1 16 FB3 = 2 V, Ta = +25 °C 4.167 4.200 4.233 V

V

Threshold voltage

V

TH2 16

Input current I

INE3 16 −INE3 = 0 V −100 −30  nA

MB3878

(Ta = +25 °C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA)

Pin
No.

Conditions

FB3 = 2 V,
Ta = −30 °C to +85 °C

Min Typ Max

4.158 4.200 4.242 V

Value

Unit

Error amplifier
block
(Error Amp.3)

Current
detection
amplifier block
(Current Amp.1,
Current Amp.2)

Voltage gain A
Frequency

bandwidth

V

Output voltage

V

Output source
current

Output sink current

OUTD pin output
leak current

OUTD pin output
ON resistor

SOURCE 15 FB3 = 2 V −2.0 −0.6 mA

I

ISINK 15 FB3 = 2 V 150 300 µA
I

R

+INCH

I

−INCH

I

Input current

+INCL

I

−INCL

I

OUTC1

V

OUTC2

Current detection
voltage

V

V

V

OUTC3

OUTC4

Common mode
input voltage

VCM

range

V 15 DC  100*  dB

W 15 AV = 0 dB  2.0*  MHz

B

FBH 15  4.7 4.9  V

FBL 15 20 200 mV

LEAK 11 OUTD = 16.8 V  01µA

ON 11 OUTD = 1 mA  70 100 Ω

+INC1 = +INC2 = 12.7 V,

13,

−INC1 = −INC2 = 12.6 V

24

+INC1 = +INC2 = 12.7 V,

1,

−INC1 = −INC2 = 12.6 V

12

+INC1 = +INC2 = 0.1 V,

13,

−INC1 = −INC2 = 0 V

24

+INC1 = +INC2 = 0.1 V,

1,

−INC1 = −INC2 = 0 V

12

+INC1 = +INC2 = 12.7 V,

2,

−INC1 = −INC2 = 12.6 V

10

+INC1 = +INC2 = 12.63 V,

2,

−INC1 = −INC2 = 12.6 V

10

+INC1 = +INC2 = 0.1 V,

2,

−INC1 = −INC2 = 0 V

10

+INC1 = +INC2 = 0.03 V,

2,

−INC1 = −INC2 = 0 V

10

 10 20 µA

 0.1 0.2 µA

−130 −65 µA

−140 −70 µA

2.25 2.5 2.75 V

0.50 0.75 1.00 V

1.25 2.50 3.75 V

0.125 0.750 1.375 V

1,
12,
13,

 0  Vcc V

24
Voltage gain A
Frequency

bandwidth

* : Standard design value.

2,

V

B

W

+INC1 = +INC2 = 12.7 V,

−INC1 = −INC2 = 12.6 V

10

2,

AV = 0 dB  2.0*  MHz

10

22.5 25 27.5 V/V

(Continued)

7

MB3878

(Continued)

Parameter Symbol

Current detection
amplifier block
(Current Amp.1,
Current Amp.2)

PWM comparator
block
(PWM Comp.)

Output voltage

Output source
current

Output sink
current

Threshold voltage

Output source
current

(Ta = +25 °C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA)

Pin
No.

OUTCH 2, 10  4.7 4.9  V

V

V

OUTCL 2, 10 20 200 mV

I

SOURCE 2, 10 OUTC1 = OUTC2 = 2 V −2.0 −0.6 mA

Conditions

Min Typ Max

Value

Unit

ISINK 2, 10 OUTC1 = OUTC2 = 2 V 150 300 µA

5, 7,

TL

V

V

TH

I

SOURCE 20

Duty cycle = 0 % 1.4 1.5  V

15

5, 7,

Duty cycle = 100 %2.5 2.6 V

15

OUT = 11 V, Duty ≤ 5 %
(t = 1 / fOSC × Duty)

−200*  mA

Output block
(OUT)

Control block
(CTL)

Bias voltage
block (VH)

General

Output sink
current

Output ON
resistor

I

SINK 20

R

OH 20 OUT = −45 mA  8.0 12.0 Ω

ROL 20 OUT = 45 mA  6.5 9.7 Ω

Rise time tr1 20

Fall time tf1 20

ON 14 Active mode 2  25 V

V

CTL input voltage

VOFF 14 Standby mode 0  0.8 V

CTLH 14 CTL = 5 V  100 200 µA

I

Input current

I

CTLL 14 CTL = 0 V  01µA

Output voltage VH 19

Standby current I
Power supply

current

CCS

I

CC

18, 19VCC = VCC (O) ,

18, 19VCC = VCC (O) ,

OUT = 16 V, Duty ≤ 5 %
(t = 1 / fOSC × Duty)

OUT = 3300 pF

(equivalent to Si4435 × 1)

OUT = 3300 pF

(equivalent to Si4435 × 1)

VCC = VCC (O)
= 7 V to 25 V,
VH = 0 to 30 mA

CTL = 0 V

CTL = 5 V

 200*  mA

 70*  ns

 60*  ns

VCC −

5.5

VCC −

5.0

VCC −

4.5

 010µA

 8.0 12.0 mA

V

* : Standard design value

8