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About LT1963ES8(ajustable LDO) application

    At first, we supplied 2.2V to the input pin and -1mA to the output pin, then we set up the shutdown pin to 5.0V(turn on the device). This process would produce a large negative voltage on the output pin and the adjust pin( the adjust pin was tied with the output pin) when it was in turned-off situation. For this device, we measured a voltage drop about 0.8V from the adjust pin to the ground, and a voltage drop about 0.6V from the ground to the adjust pin with a multimeter which is set to diode measurement mode. However, for an unused device, there is only a voltage dorp from the adjust pin the the ground, and there is not any voltage drop from ground the the adjust pin.

    I'm wondering that this powering-up process would damage the device,but now this device can work normally. Would you like to tell us whether we can continue to use the device that has been powered up in the open circuit?

    Thanks for your early reply.

Best Regards,

  • May I see the output voltage waveform during power-on? What is the peak voltage?

    The ADJ pin voltage is 1.21V when the output is regulated. Did you take the part off the board when you measured the voltage drop from ADJ to GND, and vice versa for used part? If not, please do it and check the part itself. LT1963 is robust since it has reverse current and reverse voltage protection features.