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DAC084S085: About Power-down supply current@DAC084S085

teritama
Expert 2015 points
Part Number: DAC084S085

Hi team

What is the current consumption at the VREFIN  in power-down mode?

Also, VA and VREFIN are connected together and share the same supply voltage,

if we use difference power source for VA and VREFIN, what is the current consumption at the at the VREFIN  in power-down mode?

  • 0
    TI__Mastermind 46290 points

    Hello,

    I think the best answer to this in the datasheet is on page 15 which indicates that the reference pin, VREFIN, is not buffered and therefore the input impedance from the pin is directly the four parallel resistor strings for each DAC channel for an equivalent impedance of 30kOhm. Based on that information I would not expect for the VREFIN input current to change between normal operating mode and any of the power-down modes.

  • 0 in reply to Kevin Duke
    Expert 2015 points

    Hello,

    Thank you for your answer.

    I have one more question.

    In datasheet, it is stated that the bias generator, output amplifiers, resistor strings, and other linear circuitry are all shut down in any of the
    power-down modes.

    I want to know mean of shut down of resistor strings.

    Does not mean that tha shutdown of the resistor strings is more high impedance?

  • 0 in reply to teritama
    TI__Mastermind 46290 points

    Hello,

    Of course it is not really possible to shut-down a resistor or resistors so there is a bit of a different meaning in this context. What it means to say is that the switches along the resistor string are shut-down, so the DAC code is effectively set to zero-scale and, most importantly in the context of power, the bias sources driving the switches are inactive.

    In order to deliver a high-impedance input at the reference pin, there would need to be a buffer included which is not the case for this device.

    I believe that the product definer for the original device was thinking about this on more of a system level, where the device would be powered by a reference source with an enable pin such that when in power-down mode the reference is also disabled. This is illustrated with the examples shown using the LP2980.