1.11 For higher cell counts such as 20 cells, is there any recommendation on how to
stack the bq76940 devices?
The bq76940 devices are not designed with features for external stacking. The communication and data
transfer is mostly on I2C with a few other status and control signals needed, so interfacing to a host for
higher cell count may be possible, but no stacked application diagram is currently planned or available.
1.12 Why is the DEVICE_XREADY bit high on my part and it cannot be cleared?
For the bq76930 and bq76940 it typically indicates that the voltage on the bottom cell group is adequate,
but one of the upper cell groups’ supply voltage is below VSHUT. Raise all cell group supply voltages above
VPORA and clear the status bit. Another possibility is that the part has been damaged.
DEVICE_XREADY on the bq76920 typically indicates a malfunctioned part which may need replaced.
1.13 How can I tell if the voltage readings are correct or dormant values?
If the DEVICE_XREADY is set, the voltage register values from the device should not be used. If the user
would like a way to check if the part is alive, construct a circuit that can be controlled by the system
microcontroller, which would short the thermistor on an upper cell group. The microcontroller could then
observe the voltage change based on its control and know that the part was functioning. This could be
used even if the thermistors are not used by selecting the external temperature sensing for this test. Note
that the temperature selection change may take 2 seconds to update.
1.14 Will the bq769x0 share the bus with a bq34z100?
Yes, the default (-00) bq769x0 device address (7 bit) is 0x08 while the bq34z100 address is 0x55, so they
should share the bus without issue.
1.15 What is the ALERT pin timing?
The alert pin does not have noise discrimination. It is sampled at about 256 kHz. If it is sampled high, it
will be driven high approximately 3 clocks (12 μs) later. A pulldown resistor or capacitor may help avoid
false detection on the pin. The time constant on the pulldown should allow the pin to settle below the 1-V
threshold within approximately 250 μs to avoid the part from detecting the residual ALERT pin voltage
after a status register clear.