BQ40Z60_16 Datasheet, PDF (23/47 Pages) Texas Instruments – Programmable Battery Management Unit

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Feature Description (continued)
bq40z60
SLUSAW3C – DECEMBER 2014 – REVISED JULY 2015
BAT
VC4
VC3
VC2
VC1
SRP
SRN
Pack–
Figure 4. Cell Balancing Configuration
9.3.2.3 FET Drive
The bq40z60 controls two external N-CH MOSFETs in a back-to-back configuration for battery protection. The
charge (CHG) and discharge (DSG) FETs are automatically disabled if a safety fault is detected and can also be
manually turned off using AFE_CONTROL[CHGEN, DSGEN] = 0, 0. When the gate drive is disabled, an internal
circuit discharges CHG to BAT and DSG to HSRN.
The AC FET (N-CH MOSFET) controls power input from the AC adaptor to the battery charging system by
monitoring the voltage at the VCC pin, and turning ON the ACFET if the voltage exceeds the V_HSRN voltage. The
following register command sets the AC FET gate drive output control, AFE_STATUS register (0x01) ACFET
(Pin 2): Setting this pin to 1 allows the AC FET gate drive to be on if other conditions are satisfied.
9.3.2.4 Fuse Drive
The bq40z60 AFE has the ability to blow an external fuse in the event of a permanent failure. The fuse drive
itself is supplied from the BAT input pin and its state can be monitored using the AFE_STATUS[FUSE_RAW]
register. If AFE_STATUS[FUSE_RAW} = 1 for t_DELAY duration, then LATCH_STATUS[FUSE] is set to 1, and after
an additional 500 ms, the CHG and DSG FET drive outputs will be disabled if LATCH_STATUS[FUSE] has not
been cleared by then. If the AFEFUSE output is not used, it should be connected to VSS. When AFEFUSE is in
the low state, it uses an internal weak pullup to enable detection of disconnection between the AFEFUSE pin and
the fuse drive circuitry.
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