Datasheet

IOUT1

1:1

IOUT2

50 Ω

LOAD

50 Ω

100 Ω

AGND

IOUT1

4:1

IOUT2

100 Ω

LOAD

50 Ω

AGND

DAC5672

SLAS440C –NOVEMBER 2004–REVISED DECEMBER 2010

www.ti.com

The single-ended configuration may be considered for applications requiring a unipolar output voltage.

Connecting a resistor from either one of the outputs to ground converts the output current into a

ground-referenced voltage signal. To improve on the dc linearity by maintaining a virtual ground, an I-to-V or

op-amp configuration may be considered.

Differential With Transformer

Using an RF transformer provides a convenient way of converting the differential output signal into a

single-ended signal while achieving excellent dynamic performance. The appropriate transformer must be

carefully selected based on the output frequency spectrum and impedance requirements.

The differential transformer configuration has the benefit of significantly reducing common-mode signals, thus

improving the dynamic performance over a wide range of frequencies. Furthermore, by selecting a suitable

impedance ratio (winding ratio) the transformer can provide optimum impedance matching while controlling the

compliance voltage for the converter outputs.

Figure 22 and Figure 23 show 50-Ω doubly-terminated transformer configurations with 1:1 and 4:1 impedance

ratios, respectively. Note that the center tap of the primary input of the transformer has to be grounded to enable

a dc-current flow. Applying a 20-mA full-scale output current would lead to a 0.5-V

output for a 1:1 transformer

and a 1-V

output for a 4:1 transformer. In general, the 1:1 transformer configuration will have slightly better

output distortion, but the 4:1 transformer will have 6 dB higher output power.

Figure 22. Driving a Doubly-Terminated 50-Ω Cable Using a 1:1 Impedance Ratio Transformer

Figure 23. Driving a Doubly-Terminated 50-Ω Cable Using a 4:1 Impedance Ratio Transformer

Product Folder Link(s): DAC5672