INA148: NC pin connection

Andreas Nestler

Part Number: INA148
Other Parts Discussed in Thread: , INA149

Hello, we would like to use the INA148 as primary difference amplifier IC in our design. We have an alternative IC, which we still would like to use as second source. This IC has identical pinout except pin 5, which is a second REF input and has to be connected to the other REF pin in our application. For INA148 this pin 5 is NC (no connection).

Q1: Does NC mean we must not connect to any signal or simply it is not used?

Q2: Can we safely connect Pin 5 with the REF pin signal (reference return = GND)?

Below you find the pinout figures for better understanding.

INA148/ INA148-Q1:

Second source:

Thanks in advance!.

BR Andreas

7 months ago

0 Robert Clifton56 7 months ago

TI__Mastermind 31510 points

Hi Andreas,

Andreas Nestler said:
Q1: Does NC mean we must not connect to any signal or simply it is not used?

In this case, it appears to mean that there's no connection to this pin.

Andreas Nestler said:
Q2: Can we safely connect Pin 5 with the REF pin signal (reference return = GND)?

I have a high degree of confidence that you can connect Pin 5 to ground. As seen in the INA149 datasheet, you can change out the INA148 with the INA149 which also has the same pinout as what the replacement device has.

Actually, that brings up the question, why are you going with the INA148 over the INA149? Isn't the INA149 a closer match?

Best Regards,

Robert Clifton

0 Andreas Nestler 7 months ago in reply to Robert Clifton56

Intellectual 400 points

Robert, many thanks for your reply.

Can you confirm that hard grounding of pin 5 would not lead to an unintended function or misbehaviour? I think your resource of information regarding the INA149 ist really good. I haven't checked out by myself. Regarding using the INA149 instead of INA148: We have decided to use the INA148 due to lower power dissipation (300uA vs. 1100uA). We power 20 ICs at ca. +/-15V dc so this reduced power consumption a lot by using INA148 over INA149.

Best Regards,

Andreas Nestler

+1 Robert Clifton56 7 months ago in reply to Andreas Nestler

TI__Mastermind 31510 points

Hi Andreas,

Thanks for the background information. I believe because we advertise the INA149 as a drop-in replacement for the INA148 (and vice versa) this gives me a higher degree of confidence that there shouldn't be any adverse side effects.

I went through and found another E2E with a similar question to yours. INA148: INA148 - NC pin - Amplifiers forum - Amplifiers - TI E2E support forums

It looks like you will be fine connecting ground to the NC pin.

Best Regards,

Robert Clifton

0 Andreas Nestler 7 months ago in reply to Robert Clifton56

Intellectual 400 points

Thanks!