OPA1633: Supply Question

Abigail Leonardi

Part Number: OPA1633

Tool/software:

Hi,

Quick question about supply for this device. Does it matter which supply comes up first for the OPA1633? If one supply doesn’t come up at all, is this unsafe for the part? We are feeding this part with +15V and -15V.

over 1 year ago

0 Alec Saebeler over 1 year ago

TI__Mastermind 24524 points

Hello Abigail,

Do you have an understanding of what amount of time delay there would be between the first rail coming up and the second rail coming up? If you are supplying +15V and -15V, the supply scheme would still be valid at +15V and 0V. There would be concern about your signals and appropriate results for your design, but there would not be an part reliability issue.

Could you share more about the customer board/circuit?

I will check with my time on power sequencing and start-up to see if there are recommendations.

Best,

Alec

0 Abigail Leonardi over 1 year ago in reply to Alec Saebeler

TI__Expert 3800 points

20ms between -15V, followed by +15V coming online

The power supply sequence is:

3.3V (t=0) -> -15V (t=4ms) -> +15V (t=20ms)

Additional information: the outputs of the OPA1633 could potentially be connected to a load as low as 100ohms at any time (including when powered off).

It is possible for a 3.3V signal to appear at the Enable input that precedes both the +15V and -15V rails. Do you see any issues with that?

0 Alec Saebeler over 1 year ago in reply to Abigail Leonardi

TI__Mastermind 24524 points

Hello Abigail,

I have an EVM and I can briefly test the rough behavior of the OPA1633 if the power sequencing goes ENABLE -> VS- -> VS+.

The issue with a lower load (or heavier load) would be the available output voltage swing and current drive:

I will run my quick test to examine device Iq and behavior before and after the customer startup sequence.

Best,

Alec

0 Abigail Leonardi over 1 year ago in reply to Alec Saebeler

TI__Expert 3800 points

Hi Alec, sounds great! Please let me know how it goes!

+1 Alec Saebeler over 1 year ago in reply to Abigail Leonardi

TI__Mastermind 24524 points

Hello Abigail,

During my quick testing, the following occurred:

With only PD pin set to enable device (3.3V): Iq = ~2.8mA

With -15V connected: Iq = 20mA

With both supplies connected: Iq = 11mA (as specified)

It appears the negative supply draws more than the specified Iq during this power sequencing, but the device recovers to specified quiescent current once both supplies are connected. I observed no degradation or issues with the device during this test.

I will check with my team on if this poses and issue or if we can infer the device is able to be operated with this power sequencing 20ms delay. I would advise the short nature of the 20ms delay supports the conclusion that this behavior is tolerable by the amplifier.

Best,

Alec

0 Abigail Leonardi over 1 year ago in reply to Alec Saebeler

TI__Expert 3800 points

Hi Alec, this is extremely helpful - I am passing it along to the customer!

0 Alec Saebeler over 1 year ago in reply to Abigail Leonardi

TI__Mastermind 24524 points

Hello Abigail,

Glad I was able to help!

Best,

Alec

0 Abigail Leonardi over 1 year ago in reply to Alec Saebeler

TI__Expert 3800 points

Hi Alec - I actually just noticed you're looped in directly with the customer already, I will follow up with you over there!

+1 Alec Saebeler over 1 year ago in reply to Abigail Leonardi

TI__Mastermind 24524 points

Hello Abigail,

Absolutely no worries! I do not mind when things come over to e2e, occasionally someone else will have a similar question and benefit from the answer.

Expect a response over email soon!

Best,

Alec

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OPA1633: Supply Question