BOD reset until it is reached voltage threshold in Vcc (LPC802)

[asier]

Hi, 

I want LPC802 to be reset until my power up to some level of voltage. Could I do it with BOD ? 

Thanks,

Asier.

[gusarambula]

Hello Asier,

Would you please explain with a bit more detail what functionality you want to implement with the Brown-Out Detection?

The brown-out detection circuit monitors the voltage of VDD as to assert an interrupt signal to the NVIC or issue a reset, so the system must be powered up for this function to be used.

Regards,
Gustavo

[asier]

Hello Gustavo,

The problem is that LPC802 is drawing 4mA in my circuit when it is working but when power up it seems it is drawing some extra miliAmps.

My power supply only can deliver up to 5mA and when I power uC my power supply dont get 3V3, it is measured 2V instead of, so I deduce that LPC802 is demanding more current at start up.

I think that if we leave power supply to reach 3V3 (to let capacitor charges) and then uC starts working  maybe it could deliver initial current peak that LPC802 needs. I thought that BOD could keep LPC802 in reset state until supply gets the threshold level we want. If it is not working that way, maybe I could start uC in low power mode and then get off to normal mode ? 

Thanks in advance,

Asier.

[gusarambula · Accepted solution]

Hello Asier,

One alternative would be using the reset signal so that you can keep the reset asserted until the voltage on the power supplies is stable and the capacitors are charged. Albeit this would require having a small reset circuit.

Starting on a low power mode is not possible, as you would need to first initialize the microcontroller and then setup the power configuration. Hence the current spike at startup would still be present.

My apologies for the inconvenience.

Regards,
Gustavo