BATTERY PROTECTION IC FOR 1-CELL PACK

S-8250B Series

Seiko Instruments Inc.

21



Battery Protection IC Connection Example

R1

Battery C1

VSS

DO

VDD

CO

VM

S-8250B Series

FET1

FET2

EB

−

EB

+

R2

Figure 14

Table 10 Constants for External Components

Symbol

Part

Purpose

Min.

Typ.

Max.

Remark

FET1

N-channel

MOS FET

Discharge control

−

−

−

Threshold voltage

≤ Overdischarge

detection voltage

*1

Gate to source withstand voltage

≥

Charger voltage

*2

FET2

N-channel

MOS FET

Charge control

−

−

−

Threshold voltage

≤ Overdischarge

detection voltage

*1

Gate to source withstand voltage

≥

Charger voltage

*2

R1

Resistor

ESD protection,

For power fluctuation

150

Ω

330

Ω

510

Ω

Resistance should be as small as

possible to avoid worsening the

overcharge detection accuracy due to

current consumption.

*3

C1

Capacitor

For power fluctuation

0.068

μF0.1 μF

1.0

μF

Connect a capacitor of 0.068

μF or

higher between VDD pin and VSS pin.

*4

R2

Resistor

Protection for reverse

connection of a

charger

1 k

Ω

2 k

Ω

4 k

Ω

Select as large a resistance as possible

to prevent current when a charger is

connected in reverse.

*5

*1.

If the threshold voltage of an FET is low, the FET may not cut the charge current. If an FET with a threshold voltage

equal to or higher than the overdischarge detection voltage is used, discharging may be stopped before overdischarge

is detected.

*2.

If the withstand voltage between the gate and source is lower than the charger voltage, the FET may be destroyed.

*3.

An accuracy of overcharge detection voltage is guaranteed by R1 = 330

Ω. Connecting resistors with other values

worsen the accuracy. In case of connecting a larger resistor to R1, the voltage between the VDD pin and VSS pin may

exceed the absolute maximum rating because the current flows to the S-8250B Series from the charger due to reverse

connection of charger. Connect a resistor of 150

Ω or more to R1 for ESD protection.

*4.

When connecting a resistor less than 150

Ω to R1 or a capacitor less than 0.068 μF to C1, the S-8250B Series may

malfunction when power dissipation is largely fluctuated.

*5.

When a resistor more than 4 k

Ω is connected to R2, the charge current may not be cut.

Caution 1. The above constants may be changed without notice.

2. It has not been confirmed whether the operation is normal or not in circuits other than the above

example of connection. In addition, the example of connection shown above and the constant do not

guarantee proper operation. Perform thorough evaluation using the actual application to set the

constant.