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OPA2314: Power up sequence of OPA

Part Number: OPA2314

Dear Experts:

My customer is asking us whether there is any power up sequency requirement of OPA2314. During the power up, both the input voltage and OPA 5V power supply ramp up. The input voltage at pin 3 (positive input) has chances to be higher than the power supply as below:

The input of OPA2314 is driven from on board voltage reference IC, and the output of OPA2314 will drive multiple DACs' reference input. Customer report that some devices(3 out of 200) can not buffer out  the reference input voltage correctly. By repeating power up sequence, they found that sometimes the output of OPA2314 ramp up to 3V for 1 seccond, then fall back to and stay at 0.65V. At this stable state, pin3(posistive input pin of OPA) stays at 2.5V and negative pin stays at 0.54V.   I am suspecting whether this board has soldering problem while customer denies it.

Could you please help to comments whether the device has special power up sequence? Thank you.

Yarn

  • Hi Yarn,

    The device itself doesn't have any specific power up requirements, but it is recommended to make sure that the difference between the supply voltage and the input voltage doesn't get so large that the ESD diode is forward biased. In this case, the 10k resistor would protect the ESD diode from too much current flow and there should be no issues.

    The op-amp will not behave properly until the supply voltage is stable. I agree with your assessment that something doesn't seem correct with the construction of the circuit if in a stable configuration the negative input is at 0.54V. The gain of this circuit is 1.2 V/V and the amplifier is correctly turning 0.54V into 0.65V (0.54V*1.2 = 0.65V). I would check and make sure that the input voltage is actually 2.5V.

    Hope that helps,
    Paul