DAC output help

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JR.
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Re: DAC output help

Post by JR. »

I don't see an obvious smoking gun to blame, while this shouldn't be so hard.

I repeat some of my earlier advice to consider changing around the voltage divider so DAC never sees large negative potential in any start up scenario.

JR

PS: Zener across vreg output should not be necessary, unless the spike is coming into the VREG from the output side?
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JR.
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Re: DAC output help

Post by JR. »

Has this stopped breaking, or have you stopped working on it for a while?

JR
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juniorhifikit
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Re: DAC output help

Post by juniorhifikit »

Hi - sorry I've not been visible on my own thread - busy moving from France to US.

Putting the zener diodes on the regulator outputs has eliminated the turn-on transients which seemed to be the culprit of the DAC destruction. The unit has been problem free for almost 2 months, so I'll incorporate the zeners into the final design.

I had re-orientated the bias + DAC output + filters, as we had originally discussed a long while ago to make a higher impedance between the bias feed and the DAC output, but this hadn't eliminated the problem. I had also implemented the tracking bias supply that was suggested... none of this solved the problem, so I bought a new scope, and saw the transients on the supply.

Once I incorporate the THAT1570 layout tips from member "promixe", I should have my final pcb design.
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