DS90UB954-Q1: When measuring the PCB trace return loss S11 and insertion loss S21, do i need power on the DS90UB954 ?

PYTsai

Genius 11645 points

Part Number: DS90UB954-Q1

When measuring the PCB trace return loss S11 and insertion loss S21, do i need power on the DS90UB954 ?

over 4 years ago

+1 Casey McCrea over 4 years ago

TI__Guru** 103215 points

Hello PY,

The best way to measure this is actually to remove the 954 device from the PCB and populate a 50 ohm resistor from each RIN terminal to the GND pad.

Best Regards,

Casey

0 chunyao lee over 4 years ago in reply to Casey McCrea

Prodigy 30 points

Hello Casey,

Does it mean that the suggested characteristics in 954 datasheet (table 227) is for bare PCB?

Best Regards,
Andy

0 Casey McCrea over 4 years ago in reply to chunyao lee

TI__Guru** 103215 points

Hello Andy,

The table in the datasheet is for the channel from the pin of the 954 device through the connector going out of the board and does not need to take into account the 954 device itself

Best Regards,

Casey

0 chunyao lee over 4 years ago in reply to Casey McCrea

Prodigy 30 points

Hello Casey,

I want to know whether my PCBA complies with the S11 requirement listed in table 227 .

The picture below is my measurement method.
1. Remove 954.
2. Populate a 50 ohm resistor form pin RIN+.
3. Other passive components DO NOT need to be removed.

Is that right?

Best Regards,
Andy

0 Casey McCrea over 4 years ago in reply to chunyao lee

TI__Guru** 103215 points

Hello Andy,

Yes that is correct

Best Regards,

Casey

0 chunyao lee over 4 years ago in reply to Casey McCrea

Prodigy 30 points

Hello Casey,

This is my S11 graph under the measurement method mentioned above.
I am worried about the data at 1 Mhz and 1XX Mhz. Do these two points matter?
May I have the S11 graph of 954 EVM as a reference?

Best Regards,
Andy

0 Casey McCrea over 4 years ago in reply to chunyao lee

TI__Guru** 103215 points

Hello Andy,

The return loss specification is from 1/2fBCC (25MHz) to 2.1GHz so the 1MHz value is no issue. Based on this measurement result, the S11 is well within spec.

Best Regards,

Casey

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DS90UB954-Q1: When measuring the PCB trace return loss S11 and insertion loss S21, do i need power on the DS90UB954 ?