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Original question:

DAC8760: Possible to protect it from accidental supply connection?

DAC8760: FAILURE MODE

Gabriele Pellegrinelli1
Prodigy 90 points
Part Number: DAC8760


Hi guys.

Do you know the DAC8760 failure modes?

I am particulary interested in 4-20mA current output failure mode.

Thanks.

Gabriele.

  • 0
    TI__Guru* 98275 points

    Gabriele,

    With some inductive component of a short, the IOUT may be susceptible to damage as the output goes below ground. This may violate the absolute maximum voltage listing of the device. For that, I would recommend using the same protection scheme as shown in one of the TI Designs for the DAC8760. A link for the design is shown below:

    https://www.ti.com/tool/DAC8760EMC-EVM

    Similarly, the VOUT pin is susceptible to open-to-short conditions in a similar way.

    Also, the device may also be damaged with a very fast supply ramp on the order of 1V/ns. Usually, this is prevented with some decoupling capacitance on the supply. However, the problem may still be seen when the supply is hot-socketed, especially when the socketing supply has a large mlcc-type bulk capacitance, where a significant amount of charge is delivered very quickly. We recommend that a small series resistance is inserted to slow down the supply ramp to the device. 

    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 90 points

    Thanks for your answer, Joseph.

    Is it possible to damage the DAC8760 if I put the supply voltage +VBATT (10-32V) to IOUT pin? The DAC8760 is powered by +VBATT voltage.

    What kind of failure occours in this case? Is the IOUT PMOS short-circuited?

    I'll try to explain the issue I noticed.

    I suppose I have applied the voltage +VBATT to IOUT pin. Then I remove the mistake to IOUT pin. Now, if I put a voltmeter between IOUT pin and GND I measure approximately +VBATT. Then, I'll try to change +VBATT value (from 10 to 32V) anche the voltage measure to IOUT follow the +VBATT voltage. When I put a resistor between IOUT pin and GND (47Ohm) I measure the voltage drop to this resistor around 0V (DAC is set to deliver 20mA -> 47Ohm X 20 mA = 0,94V).

    I don't undestand what kind of fault is present on the IOUT pin.

    Thanks.

    Gabriele.

  • 0 in reply to Gabriele Pellegrinelli1
    TI__Guru* 98275 points

    Gabriele,

    I wouldn't expect a voltage applied to the IOUT pin to cause damage to the device. Do you have a series resistance in your schematic coming from IOUT? In the datasheet and the EVM schematics, we use series resistances for both EMC/EMI as well as basic protection.

    However, one other thing to consider is the +VBATT voltage. If this voltage is greater than AVDD, then you may be exceeding the IOUT to GND absolute maximum voltage. This is listed on page 5 of the datasheet. When IOUT is pulled higher than AVDD, then an ESD protection diode is forward biased between the two pins. If the voltage applied to IOUT is not current limited or does not have series resistance to limit the current, then the device may be damaged. 

    Joseph Wu