I am building a self boot device using the ADAU1701 and would like to know if I need to use a delay circuit to pull the the reset pin high or can it just be connected direct to 3.3Vsupply
No, you cannot connect reset to 3.3V. The purpose is to allow for the voltage supplies to settle (and be valid) before the chip starts. The specs don't say if the input is a schmitt trigger type, to allow a RC.
If you have a uC on board, I would use it to drive reset. The reference design shows a reset generator. You could use a buffer for an RC maybe. If this is a high volume design, probably a reset generator would be best.
Thanks for the quick reply
The circuit i was looking to use is.
Do you think this is ok. I have used this with over micro controllers
Yes, I think that circuit should work. For me, rather than all those components, I would use two inverters.
But, it's possible a direct RC (and diode) might be ok. Maybe the moderator can chime in on that.
I will look at the using two inverters
The reset input does have some hysteresis, so an RC circuit should be fine. If you use this you will need to be careful that the voltage on the reset pin does not rise above Vil (0.8 V) before the IC has been properly powered-up. This will ensure that the IC boots with the reset pin held low, holding the IC in reset until the voltage rises from below Vil to above Vih.
I built the self boot circuit including the reset circuit above. I checked that all the pins had the currect voltage on them before I pulled the reset high (3.3V)
and the chip pulled alot of current and burnt out.
The chip clock was ok with reset open circuit
Pins 18,34,36,48 (3.3V)
Pins 13,24 (1.8V)
Could you either post the schematic of your design here or send it to email@example.com? It'll be easier for us to debug what's going on if we can look at the entire system.
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