Other Parts Discussed in Thread: TPS3421
Can i use/do i need external pullups on PBx inputs on TPS3420 in case of active low button that is conneted on MCU as well. I need to have system VDD on PBx lines in case not pressed.
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Hi user,
The TPS3420 has NMOS based inputs that do not require pullup resistors. For that configuration, I recommend using the TPS3421.
Thanks,
Abhinav.
I need TPS3420 version because i want that reset pulse will stay active until on of the buttons is released.
So, is only option to put MOSFET N-type infront of PBx inputs (open drain configuration) and use it to drive button press down from differrent voltage level?
Hi user,
I believe the only option is as you mentioned. In the case of pulling up a push-pull to Vcc, I believe you will have issues with functionality and notice leakage on this part.
Thanks,
Abhinav.
I have replaced TPS3420 on TPS3421EGEVM evaluation board, and also removed resistors R1 and R2 as instructed on manual.
When powered, RSTN goes high and after 7,5seconds it will stay down for until powered off. I did not even press buttons. Voltage at PBx input is zero.
Behaviour is a bit confusing to me. Inputs dont need anything to drive "high"?
Marko
I have further pulled up PB1 on VCC via 49,9k resistor while PB2 grounded.
Now, circuit seems work and current consumption is 640nA on 3.3V VCC.
Marko,
Good to see that the circuit works. If you don't mind, can you share the working schematic?
Thanks,
Abhinav.
When using TPS3421EGEVM evaluation board, dont remove pullup R1 and R2 as instructed on manual. There needs to be external pullup or push to "high" to circuit work as specified.