INA237: I2C pull-up voltage source issue

Matt Qi

Part Number: INA237

Hi,

My customer faced this question, which is given following:

INA237 owns the VIL which is 0.4V, and the low-level threshold of the front-end chip output voltage is also about 0.4V. So that they are worried about the threshold and margin.

And in the given e2e, which shows that INA237 is designed for the 1.8V I2C system: (+) INA237: VIL threshold confirmation - Amplifiers forum - Amplifiers - TI E2E support forums

Thus, my customer wants to know:

1. Whether they can make a power supply of INA237 as 3.3V, and the pull-up voltage source is 1.8V?

2. How can the power supply voltage domain and pull-up voltage source domain can influence the INA237?

For example, the power supply is 3.3V (main power), and the pull-up voltage source is 1.8V(standby power), the main power and standby power are different voltage source. Is there any influence? For example, the risk of the leakage.

Thanks and look forward to your reply.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 321960 points

1. Yes.

2. The leakage is specified in the table shown above. The I²C pins are high-impedance CMOS inputs, and when used as outputs, they are open-drain outputs that can only pull low, not high.

0 Angel Rodriguez de San Miguel Bermudez over 2 years ago

TI__Expert 8130 points

Hi Matt,

1) Yes, the pull up voltage can be different from the supply, as long as the pull up source is between 1.2V and 5.5V the device should be able to detect a logic high.

2) Having different sources shouldn't have a significant impact on the leakage current already specified on the data sheet.

I would suggest making sure the different voltage sources are referenced to the same ground to ensure that the logic level low is properly identified as a low (GND to 0.4V max).

Best Regards,

Angel