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Hello everyone,
We have lost the ability to change the gain on the LMH6401. When we read the gain at '0x02' it appears to always be clamped at '0x00' which corresponds to maximum gain.
When I try to write a new gain with '0x0B' (for example), it shows the feedback of '0X0B' when '0x02' is read but when I read it again, it's set back to '0x00'.
We have seen this before with the LMH6401 EVAL GUI and I'm not sure how it fixed itself but a few power cycles and it was back up. Not the case with the our actual HW implementation.
Any suggestions?
Iain
Hi Iain,
I assume it was working for a while and stopped? If you have a schematic and layout that would be a big help. Also what speed are you running the bus?
Best,
Sam
Hello Sam,
Thank you for the reply. Yes, it was working for a while, then stopped. Our Bus Speed is 100KHz.
Here's a snippet of the Schematic:
Here's a snippet of the Layout (center-to-center of LMH6401 and J7 is 21mm):
We're connecting to J7 with an FTDI USB to MPSSE cable: C232HM-DDHSL-0
Kindly let us know what you think?
Thank you in advance,
Iain
Hi Iain,
I'm not seeing any series resistance on the data lines? Might be worth probing those lines at the connector to see if you have ringing or timing issues. I need to do some reading on the FTDI interface in the meantime. Thank you for providing the snapshots.
Best,
Sam
Hi again,
It looks like the FTDI cable interface you are using is for 3.3V logic and the LMH6401 is designed for 1.8V logic.
Best,
Sam
Hello Sam,
I've just received word that the FTDI cables were inadvertently crossed - We are back running again (after swapping back). Thank you for all of your support.
Iain