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DAC7731: REFEN pin is suspended

Amy Luo
Expert 6895 points
Part Number: DAC7731

Hi team,

One of our customers has the following questions:

When the output of dac7731 is designed to be 0-10V and the internal reference is used, the REFEN pin is suspended and not connected to GND.

Previously, more than 100 DAC chips were processed and all worked normally, but recently several DAC chips failed to work normally. One DAC was normal after its REFEN pin was connected to GND, and others were damaged.

So want to ask the following questions

1. Does the REFEN pin have a default state? If the low level is defaulted, will the state change after long-term operation? (this article is to confirm whether the previously delivered will have potential risks)

2. Is it possible to damage the chip if the REFEN pin is suspended?

Best Regards,

Amy Luo

  • 0
    TI__Mastermind 36128 points

    Hi Amy,

    The REFEN in pin should not be left floating. There is no default state and the pin needs to be tied to VDD or GND to determine the state of the internal reference. There should be no damage to the device due to leaving the REFEN pin floating. Can you describe the behavior of the damaged devices and share a full schematic. 

    Best,

    Katlynne Jones 

  • 0 in reply to Katlynne Jones
    TI__Expert 6895 points

    Hi Katlynne,

    The damaged devices show that their output is unstable and constantly changing, even if the REFEN pin is grounded.

    schematic 

    Regards,

    Amy

  • 0 in reply to Amy Luo
    TI__Mastermind 36128 points

    Hi Amy,

    The maximum load capacitance is 200pF. I see that there is a 0.22uF capacitor on the output. Can you ask the customer to try removing this on one of the devices showing the unstable behavior? If there is no change, can you have the customer send an oscilloscope shot of the unstable output?

    Thank you,

    Katlynne Jones