ULN2803 to replace gate input transistor circuits

[widdly]

Hi,

I am building a circuit with synth 8 gate inputs feeding a 74hc165 then spi to a uc.

Each gate has a circuit something like this..

http://imgur.com/a/EezA6

I am trying to reduce my part count and board size, so I'm thinking I could replace 8 of these transistor circuits with a ULN2803. Fromt he datasheet, the inputs of ULN2803 can handle voltages up to 30v and will switch at 2V.

If I fed the incoming gates through 100k resistors to the ULN2803 inputs, then connected the ULN2803 outputs directly to the 74HC165, would that work?

[PHOBoS]

Should work but you do need to add the pullup resistors to the inputs of the 75HC165.

[widdly]

hmmm... so not much of a saving really.

[PHOBoS]

If you use a SIL resistor network, which you can also solder yourself from some resistors,
it will save some space and it is very convenient.

[wmonk]

I've used the MCP23S17 in the past, a 16-bit SPI GPIO expander.
For 8-bit, maybe http://www.microchip.com/wwwproducts/en/MCP23S08 would work?
They are highly configurable (internal pull-ups if you want, for instance) and cost about 75 cents.