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LTC6804-2 and LTC6811-2 reference voltage 1 and 2 at 0V.

Hello,

I installed 2x LTC6811-2 and then 1x LTC6804-2 on the same board and I don't have any voltage reference output at anytime. The functional diagram in the datasheets shows that VREF1 should be always present as it's generated from V+. VREF2 is not sure what generates it.

On my board, which is a copy paste of the application note of the LTC6811 (DC2560A), no reference output is present.

DRIVE is at 5.8V, VREG is at 5V, V+ is from 10V to 30V, and there is no answer from the LTC6811.

How can I probe that this is not an internal failure of the LTC6811/LTC6804 ? I it possible to check VREGD ?

What would cause 3 new parts to fail just after installation ? ESD protected area is being used.

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  • Jon,

    thanks. Yes, indeed, there is a 5kOhm pull-up on MISO and it has been checked (solder joint, trace, value)

    What is really weird, is that, in some cases, after extensive testing and probing, the SPI communication seems to work. I noticed that this happened twice when I shorted inadvertently MISO and MOSI. MISO becomes active, references are set at the right value ... even if the data-stream is not as expected (all value at stuck at 6.35V on the Linduino program).

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  • Jon,

    thanks. Yes, indeed, there is a 5kOhm pull-up on MISO and it has been checked (solder joint, trace, value)

    What is really weird, is that, in some cases, after extensive testing and probing, the SPI communication seems to work. I noticed that this happened twice when I shorted inadvertently MISO and MOSI. MISO becomes active, references are set at the right value ... even if the data-stream is not as expected (all value at stuck at 6.35V on the Linduino program).

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