Generating differential voltage output from DAC7821/AD5445?

[pavjayt]

Hi All,

I have been using DAC7821 to generate a single ended voltage output following the schematic in the datasheet as below. The current output in our config is ±5V swing

Is there a way to configure this so that it can output differential voltage using the differential current outputs from DAC directly without using an external converter?

 

[rjenkinsgb]

The DAC works by switching an array of resistor between Vref and one or the other outputs.

The currents in the resistors are only correct if the outputs are held at 0V; that's what the first opamp does, it provides a "virtual earth" at the negative input by feeding whatever current needed in to the feedback resistor to hold Iout1 at 0V.

Without the opamp, you cannot use it like that.

It may work in a different config, to give voltage out; out1 to Vref, out2 to 0V and take the output from the Vref connection.
Though the analog switches will then be working at different internal voltages and may not function.

It is one way a built-up R-2R ladder can be configured - but it's single ended and relatively high impedance, needing a voltage buffer.

 

[pavjayt]

In this case, looks like I should use something like LT6350 a SE to differential output converter. will go through its datasheet and get back if I have any questions.