
DAC5674
SLWS148A SEPTEMBER 2003 REVISED OCTOBER 2005
www.ti.com
28
AVDD
Current Source Array
IOUT1
IOUT2
S(1)
S(1)C
RLOAD
S(2)
S(2)C
S(N)
S(N)C
Figure 34. Equivalent Analog Current Output
The DAC5674 can be easily configured to drive a doubly terminated 50-
cable using a properly selected RF
transformer. Figure 35 and Figure 36 show the 50-
doubly terminated transformer configuration with 1:1 and
4:1 impedance ratio, 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 VPP for
a 1:1 transformer and a 1 VPP output for a 4:1 transformer.
Figure 37 shows the single-ended output configuration, where the output current IOUT1 flows into an equivalent
load resistance of 25
. Node IOUT2 should be connected to AGND or terminated with a resistor of 25 to
AGND. The nominal resistor load of 25
gives a differential output swing of 1 VPP when applying a 20-mA
full-scale output current.
IOUT1
1:1
IOUT2
50
50
RLOAD
50
100
AGND
Figure 35. Driving a Doubly Terminated 50-
Cable Using a 1:1 Impedance Ratio Transformer