Part Number: ISO7710
Am designing a board where i need to isolate some digital inputs. This design suppose to replace a part of an old design (a new daughter board for an existing mother board).
The inputs to this board are logic signal out of micro controller and the customer request that those outputs need to be electrically isolated from the daughter board. The problem is there is no ground signal, the old design just use a 5V rail and the i/o of the micro-controller as an open-drain with pull-up. This situation will be perfect for an opto-coupler but this open-drain is not capable of 20mA
So what am planing to do is to use the ISO7710 as isolator and power up the ISO7710 from this 5V and the this logic open-drain (VCC1 will be wired to 5V, GND and IN will be linked to the OD input, VCC2 is always powered up). i will use the model with default output high so when VCC1 is off it will have the same effect of the pull-up resistor when OD is off.
Signal speed is not high. But didn't find any information about power-up delay, since basically the device will be switching on and off. instead of toggling IN logic level.
What is the signal speed? How much current is available?
Wouldn't an optocoupler be much simpler? Why do you want to replace it with a digital isolator (are you assuming that all optocouplers need 20 mA)?
In reply to Clemens Ladisch:
totally agree an opto-coupler be much simpler, however the motherboard use a 80C51 directly connected to this daugther board. 80C51 can deliver 15mA max on a single output and something around that from the whole port. I have to use two pins that can be enabled in the same time, so this make it 7.5mA per pin. Opto-Coupler can be triggered with courant around 5mA but i think it's a bit risky. I had before some boards where opto-coupler current was too close to the minimum they stop switching after the system heat-up a bit.
In reply to BEN AMOR Hamdi32:
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