TIDA-00484: Coin cell battery discharge when VBATT become low

Ryo Akashi

Part Number: TIDA-00484
Other Parts Discussed in Thread: TPL5111, TPS3839

Hello experts,

My customer shows interest in this design. And I got question about this design from customer.

1. When coin cell battery's voltage(VBATT) become low (e.g. 2.0V, end voltage), TPL5111 open the load switch to drive MCU.

But, MCU needs some current to drive itself. In this case, VBATT drop. So, MCU can't drive

2. After turn off the load switch, VBATT recover because the load is light compared with driving MCU.

After recovering VBATT, this TPL5111 open the load switch to drive MCU.

But, same thing will occur (can't drive MCU, and turn off load switch)

My customer confirmed this phenomenon loop.

This phenomenon will lead over discharge of battery. It is dangerous.

Is there good solution to solve this loop?

Thanks and best regards,

Ryo Akashi

over 4 years ago

0 clam over 4 years ago

TI__Expert 8785 points

We are looking at this problem and will come back with some potential solutions.

0 Ryo Akashi over 4 years ago in reply to clam

TI__Expert 8370 points

Hello clam-san,

Thank you for your reply.

From my side, I have the idea to add monitoring the MCU's power supply line.(e.g. with comparators and latch circuit)

When MCU's power supply line become low, this monitoring function tell low signal to TPL5111's EN pin to stop.

But this idea need more component and more power consumption.

It is not good for this low power system design.

I would appreciate if you would give me potential solutions.

Thanks and best regards,

Ryo Akashi

0 Brian Dempsey over 4 years ago in reply to Ryo Akashi

TI__Intellectual 1425 points

Hi Akashi-san,

Have you looked into using a voltage supervisor such as the TPS3839 or the TPS3831? There is most likely no good solution that won't add at least 1 additional component. As far as current consumption concerns, the quiescent current of these two voltage supervisors is less than 1uA (150nA). I hope this helps!

0 Ryo Akashi over 4 years ago in reply to Brian Dempsey

TI__Expert 8370 points

Hello Brian-san,

Thank you for your post and sorry for my late reply.

I haven't checked TPS3839/1, but these look good. These are simple to use.

I will consider to use TPS3839 to solve this loop.

Thanks and best regards,

Ryo Akashi

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TIDA-00484: Coin cell battery discharge when VBATT become low