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Can a Dual channel DAC be operated with both output channels tied together to achieve a higher output current?

What would be possible downsides?

Background:

I require an programmable voltage source with up to 25 mA, and would have liked to do so with minimum required parts. :-)

I have an MCP4822 dual channel DAC with inbuilt op amps for both channels. Each channel typically has a "Short Circuit Current" of 15 mA (25mA is the absolute max. rating for the each output) http://ww1.microchip.com/downloads/en/devicedoc/20002249b.pdf

I probably could use the Latch DAC Input (LDAC) to keep both outputs in sync.

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    \$\begingroup\$ While LDAC might sync both at the digital end, consider the analog end. Asking two opamps to equally share the current load is a bad plan...more like an analog cat-fight. \$\endgroup\$
    – glen_geek
    Commented May 22, 2020 at 15:56
  • \$\begingroup\$ @glen_geek Indeed. It's more for synching stereo audio channels and the like. \$\endgroup\$
    – DKNguyen
    Commented May 22, 2020 at 15:57

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DACs are not meant to provide current. Short-circuit current is with output dragged all the way down to 0V by definition. Just because it can survive that doesn't mean the output voltage will be anywhere near accurate while doing so. Expect a 100% voltage droop at 15mA.

Use a buffer.

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  • \$\begingroup\$ "Use a buffer" - thanks :-) . As the MCP4822 has inbuilt output op amps, what amount of current would you still consider doable which does not affect the output voltage? Is ther e some information about this usually to be found in DAC datasheets? \$\endgroup\$
    – 0laf
    Commented May 22, 2020 at 15:54
  • \$\begingroup\$ @0laf No way to tell here. If it's not in the datasheet it's probably not good. No output impedance info. \$\endgroup\$
    – DKNguyen
    Commented May 22, 2020 at 15:56
  • \$\begingroup\$ Thanks for the edit. It will help me to ask less stupid questions in future :-) . \$\endgroup\$
    – 0laf
    Commented May 24, 2020 at 11:26

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