BQ24616: Can the safety timer be longer if I used 0.1uF +/- 20% plus the 10% accuracy on the TTC pin

Lauren Mayfield

Part Number: BQ24616

Regarding the bq24616 safety timer, te datasheet states the maximum to be 10 hours. Can the timer be more than that if you I used 0.1uF +/- 20% plus the 10% accuracy on the TTC pin?

Also, what is the recommended capacitor at the TTC pin if my battery chargers in 3.5 hours at 25 degree C?

Thanks,

Lauren

over 5 years ago

0 Kedar Manishankar over 5 years ago

TI__Mastermind 24075 points

Hi Lauren,

+/-10% safety timer accuracy is verified upto 10hrs (equates to 0.11uF capacitor from TTC to GND). Theoretically timer can be longer for slightly larger capacitance values than 0.11uF but this has not been verified and could result in larger than +/-10% error. Tchg = Kttc * Cttc, where Kttc = 5.6min/nF. For a safety timer of 3.5 hrs you would need a capacitance of about 0.38uF. The calculator tool for sizing passive components can be found here: https://www.ti.com/product/BQ24616/toolssoftware under the software link.

0 Lauren Mayfield over 5 years ago in reply to Kedar Manishankar

TI__Expert 7925 points

Do you mean 0.038uF? I am using 0.047uF at 25 degree Celsius and I'm seeing ports indicate a fault. I changed it to the max 0.1uF and the batteries charged without fault.

0 Kedar Manishankar over 5 years ago in reply to Lauren Mayfield

TI__Mastermind 24075 points

Hi Lauren,

Yes, sorry I meant 0.038uF. This capacitance corresponds to the 3.5 hour safety timer mentioned above. If charge cycle is longer, then safety timer (capacitance at TTC) should be adjusted, while accounting for the +/-10% safety timer accuracy. 0.047uF results in a 4.4hr safety timer.

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BQ24616: Can the safety timer be longer if I used 0.1uF +/- 20% plus the 10% accuracy on the TTC pin