Datasheet

Battery Protection
Cell Overvoltage and Cell Undervoltage Detection
bq77PL900
www.ti.com ...................................................................................................................................................... SLUS844B – JUNE 2008 – REVISED JANUARY 2009
The bq77PL900 fully integrates battery protection circuits including cell overvoltage, undervoltage, and
overcurrent in discharge and short circuit in discharge detection. Each detection voltage can be adjusted by
programming the integrated EEPROM. Also, the detection delay time can be programmed as shown in Table 4 .
CAUTION:
Only a maximum of three programming cycles should performed to ensure data
stability.
Table 4. Detection Voltage, Detection Delay Time Summary
PARAMETER MIN MAX STEP BITS
Voltage 4.15 V 4.5 V 50 mV 3
Overvoltage Delay 0.5 s 2.25 s 0.25 s 3
Hysteresis 100 mV 400 mV 50 mV 2
Voltage 1.4 V 2.9 V 100 mV 4
Delay 0 ms 30 ms 1.25 ms – 10 ms 4
Undervoltage
1 s 8 s 1 s
Hysteresis 100 mV 1200 mV 0.2 V, 0.4 V 2
Voltage 10 mV 85 mV 5 mV 4
Overcurrent in discharge
Delay 20 ms 1600 ms 20 ms or 100 ms 5
Voltage 60 mV 135 mV 5 mV 4
Short circuit in discharge
Delay 0 µ s 900 µ s 60 µ s 4
The cell overvoltage and cell undervoltage detection circuit consists of a sample-and-hold (S/H) circuit and two
comparators.
The S/H period is about 120 µ s for each cell, and S/H is performed sequentially on each cell. Once all of the
cells are checked, the bq77PL900 waits about 50 mS for the next S/H.
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