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DAC101C081: output of dac101C081 getting loaded

Anshul Tyagi
Prodigy 10 points
Part Number: DAC101C081

I'm using DAC101C081 to drive a LED. a led in series with a resistor is connected to the dac output. the dac is getting loaded when all ones are written to its data register, with all ones in dac data register, dac is supposed to give output 3.3V and 4.8mA. because of loading dac is able to source 3.6mA at 3.1V. need help on this..

  • 0
    TI__Mastermind 46290 points
    Anshul,

    Welcome to the E2E Community! Thanks for considering the DAC101C081 in your design, we'll be happy to help you out with your issue.

    Can you describe the properties of the resistor and the LED? Also what voltage is provided at Va of the DAc101C081?

    Based on your comments and the datasheet specification for output impedance (7.5 ohms typical), when you are driving 3.3V at the output with 3.6mA strength we can typically expect to see 3.24V at the output. The output impedance value could vary some which could account for some additional drop. Another comment would be that these output impedance specifications are collected with the output amplifier in the linear region of operation, typically with the DAC output set to mid-scale so we're well away from the supply rails. If the Va supply rail is close to 3.3V with a reference voltage of 3.3V, when at full-scale the load regulation is usually worse.

    Assuming Va is close to 3.3V, my suggestion would be to increase this voltage. Otherwise, please share the details of the resistor and LED for looking into this further.

    Thanks!