I have designed a circuit that drives a +/- 20 to 30 peak to peak external signal received as an input to 16 different outputs. Another requirement is that I have to be able to switch the state of these outputs in less than 100us (ideally 50us).
To meet these requirements, I am currently using a AQS221N2S low capacitance optocoupler array from Panasonic, precisely 4 of them. The actual circuit has been produced and tested and is functional for the specs.
However, I am now required to scale up the circuit to a 64 outputs, which brings me to reconsider my part choice for two reasons:
- AQS221N2S are relatively expensive.
- The AQS221N2S's turn on time meets the specs in the typical value (0.03ms) but not on the maximum value (0.2ms).
I cannot use relays or solid state relays as they are often slower and more expensive than the actual part.
The alternative I was considering was using an AC switch, such as the MAX14756, which is both faster and cheaper than the optocoupler solution I am using currently. Unfortunately, using an AC switch requires to add a bit of extra hardware since I will need to rectify the input AC signal to generate VDD and VSS necessary to the IC, which has the drawback of adding complexity to the design and more development time on my part.
Before I start redesigning the whole system, I was wondering if anyone had a suggestion of a part that would have the benefits of using an AC switch without the drawbacks of needing to rectify the input AC signal?
Edit: Here are some additional information about the circuit:
- The circuit is currently powered from a single Micro-USB 5V supply, then a 3.3V linear regulator is used to supply 3.3V to the circuit.
- The AC signal that I am driving ranges between 55 to 65 KHz
- The AC value given above, 20 to 30V, is a peak to peak value, it was a mistake from my part to identify it as VAC.
- Each input of the AQS221N2S are in series with a 390 Ohm resistor, giving a 5.4uA current flowing through and a switching speed below 50us according to the datasheet.