S8209A datasheet(13/22 Pages) SII

13 / 22 page

CMOS IC Application Note

Rev.1.5_00

S-8209A Series Usage Guidelines

Seiko Instruments Inc.

2. 2 Operation

Following is about the operation of protection circuit with S-8209A for series multi-cell shown in Figure 6.

Setting bipolar transistors (QCTLD1, QCTLD2) to the circuit in Figure 6 allows adding the function to transmit the

overdischarge status from the top (S-8209A (1)) to the bottom (S-8209A (3)). By this, even if any IC among the

S-8209A (1) to (3) first goes in the overdischarge status, it is possible to turn on all other cell-balance control FETs

(CBFET) of the S-8209A Series. Thus cell-balance is certainly adjusted.

Following is about the operation in the status to inhibit discharge, when the S-8209A (2) detects overdischarge,

and the S-8209A (1), (3) are in the normal status.

1. The S-8209A (2) goes in the overdischarge status when BAT2 decreases to VDL or less by discharging. The

DO2 pin is set in high impedance.

2. The S-8209A (1) also goes in the overdischarge status via the DO2 pin to the CTLD1 pin.

3. The S-8209A (1) turns on the cell-balance control FET (CBFET1) by the discharge cell-balance function.

4. The S-8209A (1) in the overdischarge status turns off DFET via a transistor (QDO, N1, N2) and inhibits

discharging to a load connected between P

+ and P−.

5. The P

− pin is pulled up by a load connected between P+ and P−.

6. QCTLD1, QCTLD2 are turned off and the CTLD3 pin of the S-8209A (3) is set in high impedance.

7. The S-8209A (3) also goes in the overdischarge status. The cell-balance control FET (CBFET3) turns on by the

discharge cell-balance function.

As mentioned above, even in case that the S-8209A (2) first detects overdischarge by voltage drop in BAT2, the

overdischarge status is transmitted from the S-8209A (1) to S-8209A (3) via QCTLD1, QCTLD2. As a result all (1) to (3)

of the S-8209A go in the overdischarge status so that cell-balance is adjusted by the discharge cell-balance

function, when each BAT is more than VDL. The cell-balance FET which corresponds to each battery turns off by

the voltages of BAT1 to 3 that decreased to VDL or less.

And QCTLD1, QCTLD2 are turned on by connecting a charger between P

+ and P− after inhibit discharging, and the

CTLD3 pin is pulled down to the level of VSS3 pin. In this case, the cell-balance control FET (CBFET3) turns off

although the voltage of BAT3 does not reach VDL or less.

Caution If a battery having the voltage VBL or more, or a battery having the voltage overdischarge release

voltage (VDU) or less is not included among batteries when composing a protection circuit shown

in Figure 6, the cell-balance control FET may turn on immediately after connecting the battery. To

turn off the cell-balance control FET, connect a charger between P

+ and P−.

S8209A bảng dữ liệu(PDF) 13 Page - Seiko Instruments Inc