TIDA-010030: about the wake-up circuit design

user6501051

Part Number: TIDA-010030
Other Parts Discussed in Thread: BQ76930

When a right charge is attached, Q15 will be turned on and pull TS1 high, and because of C20 and C18, Q15 will be turned off, generating a wake up signal on TS1 pin.

The Q15 how to turn on? If the charger voltage is 55V and the battery is 52V, the C18 has 3V, if the current from Pack+-->R59-->C18? Is right? During charge C18 to full, is the Q15 Turn off?

over 3 years ago

0 Ryan Tan over 3 years ago

TI__Expert 3345 points

Hi,

When the 55V charger is just attached, since C18 voltage is still 0V, Q15 Vgs will be 3V and turn on. Then C18 will be charged by R59/D16, when C18 is fully charger (3V), Q15 will be off.

Please click "This resolved my issue" if no more questions. Thanks.

Best Regards,

Ryan Tan

0 user6501051 over 3 years ago in reply to Ryan Tan

Intellectual 775 points

when the Q15 turn on, if the charger voltage is 55V, the R62 is 10M, so the RT1 voltage is 55*(10/(10000+360+10))=550/10370=0.0053V, is right? If the R62 10M is very big?

0 user6501051 over 3 years ago in reply to Ryan Tan

Intellectual 775 points

another question, if the battery is full, if attached the charger, if can not wakeup the BQ76930?

+1 Ryan Tan over 3 years ago in reply to user6501051

TI__Expert 3345 points

There is a C20 in parallel with R62, when Q15 is open, the RT1 voltage is: 55*(10/(360+10))=550/370=1.48V

0 Ryan Tan over 3 years ago in reply to user6501051

TI__Expert 3345 points

You are right, if charger voltage is equal to Cell13 voltage, Q15 can't be turned on. While since this circuit is used to wake up from shutdown mode, normally the pack enters shutdown mode when battery pack is quite low. Should be fine.

But I think you could change Cell13 to Cell12 or lower cell if you want to wake it up with fully charge battery.

0 user6501051 over 3 years ago in reply to Ryan Tan

Intellectual 775 points

But I think you could change Cell13 to Cell12？ i do not understand

+1 Ryan Tan over 3 years ago in reply to user6501051

TI__Expert 3345 points

I mean you could use Cell12 voltage to replace Cell13.

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TIDA-010030: about the wake-up circuit design