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Part Number: DAC8534
The outputs of DAC8534 sometimes get into a latch up state. The outputs won't change unless the board is power cycled.Is there a way to reset the DAC to an initial state and to restore the outputs without having to power cycle the system? I don'tsee any reset register in the datasheet!
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In reply to Uttam Sahu:
Attached is the schematic of DAC8534. We apply an ESD voltage of around a few hundred volts to CHAN2VDAC return and the DACs output would lock up. We are not able to change the DAC's output value unless we power cycle the board. Is there a way to reset the DAC to release it from lock up state without having to power cycle the board?
In reply to Bob Shaikhvand:
No we don't require device level ESD testing but we do ESD testing on all the I/Os. We apply ESD voltage of a few hundred volts to 4KV using1 pulse per second. Attached is the picture of ESD waveform.
Attached is also the schematic of protection circuits for the I/Os. I hate to repeat myself, but is there a way to reset the DAC8534 to an initial stateonce its outputs are locked up. The only way to get it out of the latch up state is to power cycle the board.
Bob, The only reset included in this particular device is the POR which occurs based on power supply ramps at power up - therefore the only way to issue a reset is through toggling power. The only thing we can offer you on this device is to continue examining the root cause of why the latch up state occurs and attempt to implement circuitry to prevent that. If you want to continue that discussion, please let us know. In general I would also offer some additional commentary that may be helpful for you regardless of the path you choose going forward. Be wary that reset pins and/or reset commands in firmware are not all created equal (not just for TI - this seems to present industry-wide). What I mean to say is that sometimes these are "shallow" resets which revert the user-visible register contents to their default value. This contrasts to a "deep" reset which would reset input shift registers, reload OTP / trim values, and basically issue an overall complete re-initialization of the entire device core. In many cases the "deep" reset is required to remedy a latch-up issue - assuming the latch-up isn't actually based in the analog domain where some SCR internally may have tripped. If the SCR were the root cause, though, depending on the current limit of your supply, you could see more catastrophic damage to the device. Hope this helps.
Kevin DukeDAC Applications Manager
In reply to Kevin Duke:
Thank you for your suggestions. We will try to implement your recommendations when we do a new design.As for our existing design, could we use an external signal conditioner, like an analog passive isolator, to protect DAC?
I think we will try to use an isolator for now and use the ferrite core in case we don't get proper results.
Thank you for all your help.
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