BQ78350 Wake From Sleep

Hi Jessica,

The CHG FET behavior in sleep mode is configurable by setting or clearing the DA Configuration[SLEEPCHG] flag. Just search for SLEEPCHG in the TRM.

For the DSG FET, there is no configuration but behavior depends on how sleep mode was activated. If sleep mode is entered by the gauge - that is the rules for going to sleep are valid, then the DSG FET will remain on. However, if you issue the MAC command 0x0011 to enter sleep, then the DSG FET will be turned off. Reference section 16.2.11 in the TRM.

Regards,

Doug

Thank you for the clarification.

I'm still a little fuzzy on how one would "reset" the device after a sleep event or an error event.  Is toggling the KEYb in line the typical way to turn a circuit back on?  Will that work to clear error events, or does MRSTb need to be toggled for that?

Also, can you clarify the behavior of the KEYINb line? It is a little unclear from the user reference guide how the KEYINb line affects the circuit. We've got two theories of how it could work:
1) A momentary input switch; the state of the KEYINb line directly affects the state of the DSG line (supposing delay = 0): when KEYINb line is low, DSG line is active; when KEYINb line is high, DSG line is inactive
2) A toggle switch; pressing the KEYINb line for longer than the delay time toggles the state of the DSG output line: press it once for longer than the delay time, the DSG line turns on (releasing the button has no affect); press it again for longer than the delay time and the DSG line turns off

Also, if the chip is in SLEEP, does it still react to a change in the KEYINb line? If so, does it reaction vary depending on how it entered sleep mode (i.e. by command or by low comm lines)?

Thanks again,
Jess

The KEYIN input can be used to turn the DSG FET on and off, for example in an e-bike that you want to turn on/off with a keyswitch. Non-permanent errors will recover when the fault goes away. Permanent errors will typically disable the device until you reset with a special code. See section 7.3.1 for a summary of exiting sleep mode - an SMBus transaction, current exceeding Sleep Current, or a safety fault will all do that.

Hi Jessica,

When KEYIN is asserted, a timer starts. If the time is exceeded then DSG FET is turned off.  Then, when KEYIN is deasserted the DSG FET is turned back on again. The polarity of the assert/deassert may be changed.

If the chip is in SLEEP, the KEYIN line works the same way.

Regards,

Doug

Hello Doug,

Thank you for further clarifying the behaviors for us.  We appreciate the quick responses!

Best,

Jess