Why PACK CUV protection funtion did not work ?

Jerry Zhu3

Hi,

My circuit design as below:

Charge and discharge circuit is separate,p+ is connected PACK Pin with R56(10K),CH+ is connected PACK Pin with R8(10K),

if R56 did not weld,CUV protection funtion did not work,p+ did not turn off.

if R56 and R8 all weld,CUV protection funtion did not work, and p+ turn off immediately then open again. please see the attachment video.

if R56 weld,but R8 did not weld, CUV protection funtion work normal.

Why is that? Thanks!

over 6 years ago

0 Batt over 6 years ago

TI__Mastermind 42535 points

Your R8 is going to P- so you're losing your Pack voltage reference. Besides, this part isn't designed for different chg and dsg paths.

0 Jerry Zhu3 over 6 years ago in reply to Batt

Intellectual 345 points

Hi,Batt,

Why R8 is going to P-? R8 is connected CH+(charger output).

How to modify to ensure CUV function normal?

Thanks!

0 Batt over 6 years ago in reply to Jerry Zhu3

TI__Mastermind 42535 points

If your charger isn't going high Z or open when you're discharging you are connecting it across a null connection and splitting the pack resistance. That can affect the IC operation.

0 Jerry Zhu3 over 6 years ago in reply to Batt

Intellectual 345 points

How can I solve this problem? Thanks

0 Batt over 6 years ago in reply to Jerry Zhu3

TI__Mastermind 42535 points

Try to make your charger+ high Z during dsg. Better yet, I don't understand what your need is for a different chg and dsg path. You can choose to have a common path and avoid these problems altogether.

0 Jerry Zhu3 over 6 years ago in reply to Batt

Intellectual 345 points

Hi Batt,
Thanks for your answer.
For our special application,so we need different chg and dsg path.But I still don't known how to make charger+ high Z during dsg.
Do we need to modify the circuit?

0 Batt over 6 years ago in reply to Jerry Zhu3

TI__Mastermind 42535 points

I think so. Is the charger disconnected when you're discharging the battery?

0 Jerry Zhu3 over 6 years ago in reply to Batt

Intellectual 345 points

Yes,the charger will disable when dsg.

0 Batt over 6 years ago in reply to Jerry Zhu3

TI__Mastermind 42535 points

What would be the voltage reading between GND and that point? Also what will be the voltage between P+ and that point?

0 Jerry Zhu3 over 6 years ago in reply to Batt

Intellectual 345 points

That point?you mean ch+ or pack+(pin 27)? Thanks!

0 Batt over 6 years ago in reply to Jerry Zhu3

TI__Mastermind 42535 points

CH+

0 Jerry Zhu3 over 6 years ago in reply to Batt

Intellectual 345 points

Hi,Batt,
As we known CUV is decided by cells voltage,in this case, Battery undervoltage protection is in effect，because pack' voltage change to 0 when discharging,but why it recovered again?this time cells voltage is still under the CUV Threshold.