BQ29200 Datasheet, PDF (6/15 Pages) Texas Instruments – Voltage Protection with Automatic Cell Balance for 2-Series Cell Li-Ion Batteries

bq29200
bq29209
SLUSA52 – JUNE 2010
TEST CONDITIONS
I_IN
I_IN
1 VC2
OUT 8
2 VC1
VDD 7 I_CC
3 VC1_CB CB_EN 6
4 CD
GND 5
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Figure 1. I_CC, I_IN Measurement
V_CELL
V_CELL±V_CB
1 VC2
OUT 8
2 VC1
VDD 7 I_CB
I_CB
3 VC1_CB CB_EN 6
I_{CB_EN}
4 CD
GND 5
Figure 2. I_CB Measurement
PROTECTION (OUT) TIMING
Sizing the external capacitor is based on the desired delay time as follows:
c _CD⁼
td
x_DELAY
Where t_d is the desired delay time and x_DELAY is the overvoltage delay time scale factor, expressed in seconds
per microFarad. x_DELAY is nominally 8.0 s/µF. For example, if a nominal delay of 3 seconds is desired, the
customer should use a CCD capacitor that is 3 s / 8.0 s/µF = 0.375 µF.
The delay time is calculated as follows:
td
=
éë1.2 V ´CCD ùû
ICD
If the cell overvoltage condition is removed before the external capacitor reaches the reference voltage, the
internal current source is disabled and an internal discharge block is employed to discharge the external
capacitor down to 0 V. In this instance, the OUT pin remains in a low state.
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