Post Go back to editing

LTC3638 in the Output Voltage Programming mode


I have designed an electronic circuit and am using the LTC3638 in the Output Voltage Programming mode.

The circuit and configure so that it operates a 120 AVC at the input and 11 volts at the output. May I have problems the circuit works fine when I apply 120v on the input and have 10.98volts on the output. The problem is when I apply a load which is a single LED the circuit stops working and I have to replace the LTC3638.

See the schematic
Thank you for your help!


  • Hello Chris,

    for further problem evaluation we would need a datasheet from the used LED.
    The LTC3638 is a part which delivers a constant voltage. Normally LEDs require a constant current and have reasonable changes due to the steep V/I curve. If your LEDs draws too much current with your fixed output voltage the LTC3638 might get overloaded.

    You might want to limit possible output current by using ISET pin, description is in the datasheet (Resistor between ISET and GND). Start with small current values for testing.

    A LTSpice simulation might reveal this overcurrent event without destroying real hardware.