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Original question:

MAX3221: Device not working

MAX3227: Chip is not working, problem with AutoShutdown

Troy Sims
Prodigy 20 points
Part Number: MAX3227

I am using the MAX3227 chip and I have it interfaced as such,

On boot, V+ and V- are 2.5 V instead of 5.5V. Ready pin is low and Invalid pin is low. (It doesn't go to 5.5 V at all on boot, which makes me think it is going directly into shutdown).

On the Rin, I have a test probe connected to an external device with a -5V signal (stable as the device I am connected to only responds when given a command). On the Din, I have a TTL signal coming from an FPGA that is sending the command. I have checked the Din and it is sending the TTL command signal.

I have tested all of my equipment on a breadboard and it was working fine the only difference was that I had the FORCEON driven high to force normal operation.

The AutoShutdown seems to not be working as I have a valid Rin signal and I should be getting edge detection on the Din side. I am unsure what I am doing wrong on my side.

  • 0
    TI__Mastermind 45767 points

    Hi Troy,

    I have a few questions:

    1. So does the device work normally when you drive the FORCEON pin high and only isn't working when it's configured like in the above schematic?

    2. Is it possible to get an approximate current draw from the VCC pin - there should be a large difference between active and shutdown level currents?

    3. Can you take a picture of the top of the suspect unit and attach it as a reply in the post - I want to confirm the device is legitimate in our system - it's not usually an issue - but I would like to double check. 

    Overall - it looks like the schematic is okay and based on your description it sounds like the /INVALID pin and READY pin should be going high based on your actions - if you can answer my other questions above we can look at what the next best steps are.

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Prodigy 20 points

    Upon further inspection, our PCB was causing the issues not the part.