MB3879 データシートの表示（PDF） - Fujitsu

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MB3879

DC/DC Converter IC for Parallel Charging of 3/4 cell Li-ion & NiMH Batteries

Fujitsu 

MB3879

2. VDD Logic Block

(1) Control block (CTL)

The system is placed under standby mode by setting CTL terminal (pin 7) to "L" level (power supply current is

a maximum of 10 µA under standby mode). Setting "H" level at CTL terminal generates an internal reference

voltage, placing the system under output operation status.

After setting "L" level at CTL terminal, CTL signal reactivation time (tRCTL=2ms(Min)) is required to set the "H"

level signal.

(2) Decoder block (DEC)

By applying signals to D0 terminal (pin 2) through D3 terminal (pin 5), the 4-bit decoder section (DEC) selects

output voltage among 12.6V (3 cells), 12.3V (3 cells), 16.8V (4 cells), and 16.4V (4 cells). The voltages are

applicable not only to Li-ion batteries but also to NiMH batteries that require cancellation of output voltage control.

(See " DECODER SECTION OUTPUT VOLTAGE SETTING CODES" for details.)

(3) Mode detection block (MODE Comp.)

The mode detection block outputs which charge mode to OUT-EA1 terminal (pin 13), OUT-EA2 terminal (pin

12), OUT EC terminal (pin 11), and OUT-EV terminal (pin 10). For dynamically-controlled charging mode, OUT-

EA1 terminal is set to "L" level and OUT-EA2 terminal, OUT-EC terminal, and OUT-EV terminal are set to "H"

level. For Differential-charging mode, OUT-EA2 terminal is set to "L" level and OUT-EA1 terminal, OUT-EC

terminal, and OUT-EV terminal are set to "H" level. For Constant-current charge mode, OUT-EC terminal is set

to "L" level and OUT-EA1 terminal, OUT-EA2 terminal, and OUT-EV terminal are set to "H" level. For Constant-

voltage charge mode, OUT-EV terminal is set to "L" level and OUT-EA1 terminal, OUT-EA2 terminal, and OUT-

EC terminal are set to "H" level.

Using DTC terminal (pin 39), duty setting from external device is allowed. In such a case, set all of OUT-EA1

terminal, OUT-EA2 terminal, OUT-EC terminal, and OUT-EV terminal to H level when FB terminal voltages of all

error amplifiers are higher than DTC terminal voltage.

3. Control Function

Specifies settings of "on" and "off" of outputs with setting conditions of CTL terminal (pin 7).

"On" and "off" settings of outputs

Voltage level of CTL terminal

L

H

"On/off" status of output

OFF (standby mode)

ON (operating mode)

4. Protection Functions

(1) Undervoltage lockout protection circuit block (UVLO)

The transient state or a momentary decrease in power supply voltage (VCC) or internal reference voltage (VB),

which occurs when the power supply is turned on, may cause the control IC to malfunction, resulting in breakdown

or degradation of the system.

To prevent such malfunctions, the undervoltage lockout protection circuit detects decrease of the internal refer-

ence voltage level with respect to the power supply voltage and internal reference voltage, and holds OUT

terminal (pin 24) on output terminals at "H" level. The circuit restores the output transistor to normal when the

supply voltage and internal reference voltage reach the threshold voltage of the undervoltage lockout protection

circuit.

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