Needs to powered or not?

Support
1

Hello All,

I am beginning the debugging process for a decoder using the Saleae logic analyzer. I have a few questions for clarification. Thank you all in advance for your answers.

Background:
I work for a PCBA company, and I need to debug an IC that is mounted on a board.
I have scraped the circuit trace (SDA, SCL, and CHG) to solder wires and clip them using the Saleae test clips.

Questions:

  1. Do I need to power the IC? I mean, do I need to supply power to VDD or AVDD? I tried using the Saleae, and I received results. Does the power come from the laptop? Also, does a three-prong laptop charging cable act as GND?

  2. What is the correct procedure to obtain accurate results?
    Option 1: Charging laptop + No need to power the IC
    Option 2: Unplugged laptop (not charging) + Powered IC

By “power the IC,” I mean connecting the negative (-) terminal and GND from the power supply to the PCBA’s GND, and connecting the positive (+) terminal from the power supply to the test pin on the PCBA that is connected to the IC’s AVDD or VDD pin.

2

Hello,

Thanks for writing in!

Let me start with a bit of background to help explain what you should expect.

Our products are record-only. They should not interfere with the operation of the circuit you are trying to debug.

This means that in order to record traffic using our products, your device needs to already produce that traffic, otherwise there will be no traffic to record.

This usually means that your device will need to be powered up and also be capable of generating it’s own traffic. If your IC needs power to function, you will need to make sure it’s powered up. Our products don’t provide power themselves.

For connecting signals, we have a basic setup guide here: Setup | Saleae Support
And a more advanced probing guide here: Logic Analyzer Tutorial: Probe Setup | Saleae Articles

If you would like more guidance, please tell us more about the IC you are testing, what else it is connected to on your PCB, and what you are trying to debug.