TPL5111: TPL5111 work as timer

Hi Lane,

Customer tested TPL5010 and they think it is not match with their application.

Customer want TPL5010 will reckon the time when initial power up, MCU will send a commend to driver MOSFET when watchdog timer expires. But currently, MCU will get a commend when TPL5010 initially power up.

So any way to avoid this?

Thanks.

Best regards,

Sammi

Hi Sammi,

I only suggested TPL5010 because it has watchdog timer function. If the customer doesn't need that functionality, TPL5111 should be fine.

Will TPL5111 work for the customer? Can you send me a diagram of the timing the customer needs to generate?

What behavior are you trying to avoid with TPL5010?

Kind regards,
Lane

Hi Lane,

Thanks for your reply. Actually customer need is a timer, we recommend LMC555 before. What customer need is: power up-->timer up to 12s-->MCU send recommend. But due to customer's design(only power by a capacitor), LMC555 is not stable. Then we change to find if a watchdog timer works.

Currently customer did not pass the test both for TPL5010 and TPL5111. But they tested and found when initial power up, MCU will communicate with watchdog. This is not what they want, they want the IC timer just last 12s and then send commend to MCU.

Hope this could help you understand the question.

Thanks.

Best regards,

Sammi 

Hi Sammi,

If I understand correctly, the customer just needs a logic output from the timer after the 12s timer elapses. In this case, TPL5010 could work in one-shot mode.

I calculate Rext = 8.99K for 12s time interval. The customer would not provide an input on the DONE pin. After the 12s timer elapses, there is a 320ms LOW pulse on RSTn. Or the customer can use the WAKE output.

If the customer does not need the output on the RSTn pin, TPL5111 can be used. TPL5111 can be set to ONE SHOT mode instead of timer mode, in case you only want timing for the first cycle. TPL5111 has no RSTn pin for WDT control, so you must use the DRV pin.

If it still is not possible to generate the desired timing using these devices, the customer might try with 555 timer again. Perhaps use an LDO on the supply.

Kind regards,
Lane

Hi Lane,

Thanks for your suggestion. I checked with customer again, current obstacle is that when initial power up, suppose time interval delay is high level '1', time over is low level '0'. When testing TLP5111 and TLP5010, initial power up, both two IC will export an '0' level to MCU first, then begin to time keeping. But customers' application is one shot, so when initial power up, MCU will think the time interval has ended.

Would you kindly help confirm if this could be avoided?

Thanks.

Best regards,

Sammi

Hi Sammi,

I understand the issue, but this cannot be fixed within TPL5111. I think the customer must address it at a system level with the MCU. 

If the device is configured for one shot, and the DRVn has returned low, it makes sense that the MCU thinks the time interval has expired.

Kind regards,
Lane