TLC2543 self test, BS2p40

Piper984

Hello gang,

I had a PCB made that uses BS2, an op-amp and a TLC2543 A/D.· I tested the circuit using a BS2 and BOE before ordering the PCB.· Now, of course, the PCB arrives and I get all 0's back from the TCL2543.· Does anyone know what the 'self test' procedure looks like for a TCL2543 and what BS2 code would look like to trigger it?· I have looked at the circuit laid out on the PCB, and can't locate any issues. A self test procedure would sure help me isolate if the issue is in the PCB design, the PCB fab, a component, etc.

Anyone?· Tracy?· Help!

·

Tracy Allen

Well, without detailed information, it is hard to say! It comes down to good old fashioned troubleshooting. Are the power supply and references all correct and on the correct pins? One common mistake is reversing the SHIFTIN and SHIFTOUT pins. Look at the signals on a 'scope if you have one, and make sure they are showing up on the correct pins. That will usually reveal some issue that will help you resolve the problem.

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Tracy Allen
www.emesystems.com

Piper984

Hello Tracy,

Thanks for the advice.· I did indeed have I/O crossed, and all seems to be working now.

But just for my own information: The TLC2543 whitepaper talks about a self test mode.· Have you ever invoked this from a BS2?

Regards!

Tracy Allen

I think it refers to "test inputs" and then "power-down mode". Not "test mode".

The test inputs are internal connections to Vref-, Vref+ and (Vref+ - Vref-)/2. You convert those voltages in the normal manner by sending a command request for the test channels 13, 12 or 11. I don't find them very useful, except I address channel 11 at power up or after wakeup, to force a dummy throw-away conversion, so that the chip is properly initialized.

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Tracy Allen
www.emesystems.com