It is a good question: Is setting an output to zero equivalent to grounding the device connected to the output?
The answer is: Not exactly. You did not specify whether you are asking about an analog output or a digital output. In both cases the direction and magnitude of the current flow are significant.
The digital output is a transistor conducting to ground. The absolute maximum negative voltage limit is 0.5 V below ground. The device is not specified for current flow out of the output when the output is low. The transistor probably conducts somewhat in the reverse direction, but you would not have any idea of the internal resistance or what limit it could withstand without damage.
The analog output circuit is shown as a buffer amplifier with a 50 ohm output resistance. Since the power supply is zero and five volts, it is highly unlikely that the amplifier can source current at zero volts.
So, for your application: If you are certain that the current will always flow into the output at zero volts and the internal resistance is small compared to the R in your external circuit, then the output can be switched as described. If both of those conditions are not met, you will introduce errors and may damage the DAC device.
Lynn
