IG502 DOUT - how to ensure DOn is not driven low after boot.
Does any one know of a way to configuring the device so it starts up and doesn't drive the digital outputs low by default?
The IG502 has low side drivers for DO0-3 with weak pull ups to 5~6V, This makes it very easy, and is the typical way, to drive relays. One side of the coil goes to +ve supply, and the other side of the coil goes to a DO.
The problem is that after reset, and after the system has booted, each bit controlling each DO is set to 0 - which turns ON the low side driver (i.e. it is connecting DO to GND). This turns on the relay. Looking with a scope or voltmeter, you would see some seconds of a 'high' level followed by the 'low' level.
I cannot use the 'retentive setting' since if power is lost and then re-applied, I need to guarantee the relays will be in a safe state (OFF).
If this was a code running on a microcontroller, and we were only using low side drivers, we would not turn on any until they were actually required.
In the meanwhile, is there some other solution?
Thanks,
David.
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1 replies
dhowells
Another option might be to have a setting which 'inverts' the output. So writing a zero sets the output high, writing a one sets the output low. This is also more logical when a digital output is low-side only.