Running a MCP23017 on 5V

apuder
Posts: 32
Joined: Mon Mar 26, 2018 7:27 pm

Running a MCP23017 on 5V

Postby apuder » Sun Feb 16, 2020 6:43 pm

Hi,

I want to use the MCP23017 port expander for a project. The logic I'm driving with the MCP23017 is on 5V so I want to use 5V to power the MCP23017. My question is: since SDA and SDC are open drain connections on the I2C bus, is it OK to use the ESP to drive the MCP23017? The ESP has internal pullups to 3.3V on its I2C port so I think it should be fine. However, the datasheet for the MCP23017 has some AC characteristics in section 1.2: http://ww1.microchip.com/downloads/en/D ... 01952C.pdf

It shows a pullup to VDD in that schematics. Is that an internal pull in the MCP23017? I could not find any indication.

Long in short: is it OK to connect an ESP via I2C to a MCP23017 running on 5V without any level-shifters?

TIA,
AP

username
Posts: 156
Joined: Thu May 03, 2018 1:18 pm

Re: Running a MCP23017 on 5V

Postby username » Mon Feb 17, 2020 3:31 am

That AC diagram your referring to is to show what the pin with those loads will meet for the timing specifications.
Yes, you can power the MCP23017 from 5V. The only thing you need to do is run your 2 pullup resistors to +3.3v and not +5v

apuder
Posts: 32
Joined: Mon Mar 26, 2018 7:27 pm

Re: Running a MCP23017 on 5V

Postby apuder » Mon Feb 17, 2020 4:51 am

Thanks for your response. Just to clarify on the pull-ups: the built-in pull-ups that get enabled with sda_pullup_en and scl_pullup_en of i2c_config_t are sufficient, correct?

AP

ESP_Sprite
Posts: 3253
Joined: Thu Nov 26, 2015 4:08 am

Re: Running a MCP23017 on 5V

Postby ESP_Sprite » Mon Feb 17, 2020 10:08 am

It could work but wouldn't count on it if you want a high-speed bus: internal pull-ups are 50K'ish while I2C normally wants something in the 5K range.

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