TCA39416: Connecting more than one PGA2505 5V SPI part to a 3V3 SPI bus?

Graham North1

Part Number: TCA39416
Other Parts Discussed in Thread: PGA2505, SN74LVC1G125, SN74AHC1G125

Tool/software:

I need to put more than one PGA2505 into a design that has other SPI devices and a processor that runs at 3V3. From the datasheet and evaluation board design it looks like 3V3 level SPI signals work fine going from the processor to the PGA2505 parts, and it is only the MISO lines that I will need to levelshift.

So I'm looking for a simple buffer with an !OE pin that will tristate its output, but will also levelshift. Does such a part exist? Or are there other ways to do this?

Thanks,
G

5 months ago

0 Clemens Ladisch 5 months ago

Guru 316780 points

You can use any buffer with overvoltage-tolerant input, e.g., SN74AHC1G125, SN74LVC1G125.

0 Graham North1 5 months ago in reply to Clemens Ladisch

Intellectual 405 points

I'm not familiar with those parts, and the datasheet is fairly slim.

Do I just power it form 3V3 and it is totally fine to connect a 5V logic level signal to it's input? Do I need to current limit the input signal or anything?

Thanks,

0 Clemens Ladisch 5 months ago in reply to Graham North1

Guru 316780 points

Yes, they accept input voltages higher than their own V_CC. The inputs have a high impedance; see the I_I specification. Also see [FAQ] Can the input voltage (Vi) to my logic device be higher than the supply voltage (Vcc)?

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TCA39416: Connecting more than one PGA2505 5V SPI part to a 3V3 SPI bus?