INA226: How strong should the adress pins be pulled to VSS, VCC, SDA or SCL?

Niek ten Brinke

Part Number: INA226

Okay, I have the following case:

Board 1 is a backplane board and has some (multiple) insertable boards in the shape of board 2. Board 2 has local power supplies that we don't want to cross over to board 1 due to various reasons. Now what we want to do instead is have a weaker pull resistor that is always placed and then depending on the address that is desired one of the 3 optional resistors can be placed on board 1. Now my question is this possible for the 0R to SDA or SCL? What would be resistor values that work?

Thanks in advance!

over 2 years ago

0 kai klaas69 over 2 years ago

Guru 140200 points

Hi Niek,

this may help:

slva689.pdf

Kai

0 Mitch M over 2 years ago

TI__Mastermind 26105 points

Hello Niek,

In general we actually recommend connecting the address pin directly to VS/GND/SDA/SCL without any resistor. So, I recommend 0Ω resistors for all 4 cases above.

Regards,

Mitch

0 Niek ten Brinke over 2 years ago in reply to kai klaas69

Prodigy 10 points

Hi Kai,

These are pull-up resistors on the I2C pins to VCC. I know how to calculate those. What I want to know is can I have a pull resistor to 3V3 and then override it with a stronger resistor to either SDA, SCL or GND. And I don't see recommendations in the application note for that. Thanks anyhow!

Kind regards, Niek

0 Niek ten Brinke over 2 years ago in reply to Mitch M

Prodigy 10 points

Hi Mitch,

Okay... but that's not really an option as I can't change every board 2 (as these are insertable modules). And as mentioned, running 3V3 over the connection is not preferred. The reason for this is that it then also requires fusing etc. which increases the BOM costs, area and so on. Also I want to avoid 0R in general as Board 2 is also hot-swappable.

0 Mitch M over 2 years ago in reply to Niek ten Brinke

TI__Mastermind 26105 points

Hello Niek,

Ah, ok, I see what you are saying now. In terms of addressing, 0Ω would be best for SDA/SCL, but I see why you are wanting to use some resistance. I'll look into this more to see if it will still reliably work with resistors for the SDA/SCL option, and try to get back to you by tomorrow.

Regards,

Mitch

+1 Mitch M over 2 years ago in reply to Mitch M

TI__Mastermind 26105 points

Hey Niek,

We don't have any official recommendation for resistance on the SDA/SCL address pins, but talking with my colleagues, we think you should be fine if you keep the resistance below 1KΩ. (But the smaller the better).

Regards,

Mitch

0 Niek ten Brinke over 2 years ago in reply to Mitch M

Prodigy 10 points

Thank you Mitch! The only think I would have to be careful is that the 'always on' pull-up resistor will also act as pull-up on the SDA/SCL (make sure that the total resistance doesn't get too low

0 Mitch M over 2 years ago in reply to Niek ten Brinke

TI__Mastermind 26105 points

You're welcome! Let me know if you end up having ay further questions.

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INA226: How strong should the adress pins be pulled to VSS, VCC, SDA or SCL?