BQ76940: OVRD_ALERT Cannot be reset

Hi Mark,

The OVRD_ALERT bit clears by writing a high like other bits in the BQ76940 status register, however a common reason for the bit to be set is that the ALERT pin did not fall fast enough when the status register was cleared and was detected high causing a latch condition.

When the status register is cleared, ALERT pulls down weakly.  At about 500 us after clear the part starts to look at the pin as an input.  If the pin has not fallen sufficiently OVRD_ALERT will be set and ALERT will be driven high again.  Common causes are large capacitance on the signal, or no external pull down. Also check for crosstalk coupling to the line.  When a noise filter capacitor is added to the signal the time constant should be kept to about 250 us or less.  You might inspect the ALERT signal with a scope at the time it is cleared to see if it is going low or is a short sawtooth pulse low.