MCP42100 powered by 3V3 to control a circuit powered by 5V ?

[ggchab]

Hello,
May I use an MCP42100 powered by 3V3 (microcontroller and SPI bus in 3V3) to control a circuit (op amp) powered by 5V ?
Thanks

[MasterT]

It says on page 5 in data sheet :
Absolute Maximum Ratings †
VDD...................................................................................7.0V
All inputs and outputs w.r.t. VSS ............... -0.6V to VDD +1.0V

For your 3.3V maximum would be 4.3V. No way 5.

[ovnr]

No; also, the spec'd input thresholds indicate that you can't power it off of 5V and still use a 3.3V SPI bus.

Just use a level shifter and power it off of 5V - either a dedicated chip or some transistors and resistors.

[mikerj]

Hello,
May I use an MCP42100 powered by 3V3 (microcontroller and SPI bus in 3V3) to control a circuit (op amp) powered by 5V ?
Thanks

It depends entirely on the actual voltage that is going to be applied to the digital potentiometer, provided this is not more than 3.3v then it will be fine.  People seem to be assuming that because the op-amp has a 5v supply rail that 5v will be applied to the digitpot, this isn't necessarily the case (though equally it might be).

Posting a schematic of your proposal would help.

[Zero999]

My guess is the original poster has misused the word powered.

The MCP42100 needs to be powered from the same power supply as the op-amp. Unfortunately the high threshold voltage is equal to 0.7*V_DD, which would be 3.5V, in this case, so a level shifter is required.

There's a small breakout board available or you can copy schematic off the Sparkfun website. Then there are ICs, such as CD4504, 74HCT126, 74HCT241, 74HCT244 (3.3V to 5V) and 74HC4050 (>5V to <6V).
https://www.sparkfun.com/products/12009

[ggchab]

Thanks to all.
I'll power the MCP44100 in 5V and use a level shifter for for CS, MOSI and SCK lines. I don't have to care about MISO as it's not used