No output from DAC8560

Emmett Bradford

Intellectual 425 points

Other Parts Discussed in Thread: DAC8560

I have a DAC8560 on 2 prototype PCBs.

They both behave the same, VREF is putting out, but the DAC output does not no matter what code is sent to it.

I have verifed the SPI inputs with logic analyzer an oscope.

I ordered more parts in case I have 2 bad parts, but I doubt it.

Please see the attached logic analyzer traces and circuit.

Am I doing something wrong?

over 12 years ago

0 Emmett Bradford over 12 years ago

Intellectual 425 points

DAC8560 SPI Zoom.jpg shows clock phasing

0 Emmett Bradford over 12 years ago in reply to Emmett Bradford

Intellectual 425 points

Circuit

0 Kevin Duke over 12 years ago in reply to Emmett Bradford

TI__Mastermind 46290 points

Emmet,

What is the input logic high voltage you observe on the DAC8560 side of the resistors on your serial bus?

0 Emmett Bradford over 12 years ago in reply to Kevin Duke

Intellectual 425 points

Vi > 3V

Vdd = 3.3V

No noticeable drop across the series resistors.

Thanks,

Emmett

0 Kevin Duke over 12 years ago in reply to Emmett Bradford

TI__Mastermind 46290 points

Can I see the oscilloscope captures? Also, how is this physically assembled? Breadboard? PCB? EVMs?

0 Emmett Bradford over 12 years ago in reply to Kevin Duke

Intellectual 425 points

Here's the scope pictures.

The IC is on our prototype 4-layer PCB w/ a ground plane and everything

0 Emmett Bradford over 12 years ago in reply to Emmett Bradford

Intellectual 425 points

The other picture.

Can't add more than one file at once?

0 Kevin Duke over 12 years ago in reply to Emmett Bradford

TI__Mastermind 46290 points

I'm a little stumped...

What value does the reference voltage start up at? I've heard of some latch-up problems at power up with this part in the past, usually a tell for this condition is the reference voltage seeing some offset.

0 Emmett Bradford over 12 years ago in reply to Kevin Duke

Intellectual 425 points

Now it's working!

Don't know why!

Nothing SPI is different.

Vref is now 2.5V, don't know exactly what it was before, but every time I looked at it, it was near that.

I'll try to get it to fail again.

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No output from DAC8560