BQ29441 Datasheet, PDF (8/17 Pages) Texas Instruments – Voltage Protection for 2-Series, 3-Series, or 4-Series Cell Li-Ion Batteries

bq29440, bq2944L0
bq29441, bq29442, bq29443, bq29449, bq2944L9
SLUSA15C – JUNE 2010 – REVISED NOVEMBER 2010
CELL CONNECTION SEQUENCE
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NOTE
Before connecting the cells, propagate the overvoltage delay timing capacitor, C_CD.
The recommended cell connection sequence begins from the bottom of the stack, as follows:
1. GND
2. VC4
3. VC3
4. VC2
5. VC1
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. VC4, VC3, VC2, or VC1
3. Remaining VCx pin
4. Remaining VCx pin
5. Remaining VCx pin
CUSTOMER TEST MODE
Customer Test Mode (CTM) helps to greatly reduce the overvoltage detection delay time and enable quicker
customer production testing. This mode is intended for quick-pass board-level verification tests, and, as such,
individual cell overvoltage levels may deviate slightly from the specifications (V_PROTECT, V_OA). If accurate
overvoltage thresholds are to be tested, use the standard delay settings that are intended for normal use.
To enter CTM, VDD should be set to approximately 9.5 V higher than VC1. When CTM is entered, the device
switches from the normal overvoltage delay time scale factor, x_DELAY, to a significantly reduced factor, x_{DELAY_CTM},
thereby reducing the delay time during an overvoltage condition. The CTM overvoltage delay time is similar to
the equation presented in PROTECTION (OUT) TIMING AND DELAY TIME CAPACITOR SIZING with the
substitution of x_{DELAY_CTM} in place of x_DELAY:
t_{d _ CTM} = C_CD ´ X_{DELAY_CTM}
CAUTION
Avoid exceeding any Absolute Maximum Voltages on any pins when placing the part
into Customer Test Mode. Also, avoid exceeding Absolute Maximum Voltages for the
individual cell voltages (VC1–VC2), (VC2–VC3), (VC3–VC4), and (VC4–GND).
Stressing the pins beyond the rated limits may cause permanent damage to the
device.
To exit CTM, power off the device and then power it back on.
For latched versions of the bq2944x, the external C_CD capacitor must be externally discharged if any overvoltage
functionality is exercised during protection testing. This can be accomplished by shorting the CD pin to GND. If
the C_CD capacitor is not explicitly discharged, a residual charge may cause the overvoltage delay time to be
inaccurate.
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