BQ29200 Datasheet, PDF (7/15 Pages) Texas Instruments – Voltage Protection with Automatic Cell Balance for 2-Series Cell Li-Ion Batteries

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bq29200
bq29209
SLUSA52 – JUNE 2010
Cell Voltage > V_PROTECT
When one or both of the cell voltages rises above V_PROTECT, the internal comparator is tripped, and the delay
begins to count to t_d. If the input remains above V_PROTECT for the duration of t_d, the bq2920x output changes from
a low to a high state, by means of an internal pull-up network, to a regulated voltage of no more than 8.5 V when
I_OH = 0 mA.
The external delay capacitor should charge up to no more than the internal LDO voltage (approximately 5 V
typically), and will fully discharge in approximately under 100 ms when the overvoltage condition is removed.
Cell Voltage
VC2-VC1,
VC1-GND
V PROTECT
VPROTECT - VHYS
t_d
OUT
L
H
Figure 3. Timing for Overvoltage Sensing
CELL CONNECTION SEQUENCE
The recommended cell connection sequence begins from the bottom of the stack, as follows:
1. GND
2. VC1
3. VC2
While not advised, connecting the cells in a sequence other than that described above does not result in errant
activity on the OUT pin. For example:
1. GND
2. VC2 or VC1
3. Remaining VCx pin
It is also recommended that the overvoltage delay timing capacitor, C_CD, be propagated before connecting the
cells.
CELL BALANCE ENABLE CONTROL
To avoid prematurely discharging the cells, it is recommended to turn off (pull high) the active-low Cell Balance
Enable Control pin at lower State of Charge (SOC) levels.
BATTERY CONNECTION
Figure 4 shows the configuration for the 2-series cell battery connection.
Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): bq29200 bq29209
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