Agilent Technologies 93000 SOC Series Training Manual page 604

THS5641A
8-BIT, 100 MSPS, CommsDAC
Appendix C
DIGITAL-TO-ANALOG CONVERTER
SLAS277A –MARCH 2000 – REVISED SEPTEMBER 2002
IOUT1
IOUT2
(a)
Figure 27. Differential and Single-Ended Output Configuration
The THS5641A can be easily configured to drive a doubly terminated 50 Ω cable. Figure 28(a) shows the
single-ended output configuration, where the output current IOUT1 flows into an equivalent load resistance of
25 Ω. Node IOUT2 should be connected to ground or terminated with a resistor of 25 Ω. Differential-to-single
conversion (e.g., for measurement purposes) can be performed using a properly selected RF transformer, as
shown in Figure 28(b). This configuration provides maximum rejection of common-mode noise sources and
even order distortion components, thereby doubling the power to the output. The center tap on the primary side
of the transformer is connected to AGND, enabling a dc current flow for both IOUT1 and IOUT2. Note that the
ac performance of the THS5641A is optimum using this differential transformer coupled output, limiting the
voltage swing at IOUT1 and IOUT2 to ±0.5 V.
50 Ω
IOUT1
IOUT2
25 Ω
18
APPLICATION INFORMATION
50 Ω
+)
VOUT
–)
50 Ω
VOUT
50 Ω
(a)
Figure 28. Driving a Doubly Terminated 50 Ω Cable
604
POST OFFICE BOX 655303
–
IOUT1
+
IOUT2
50 Ω
1:1
IOUT1
100 Ω
IOUT2
50 Ω
•
DALLAS, TEXAS 75265
C FB
R FB
100 Ω
+)
VOUT
THS4001
–)
THS4011
(b)
VOUT
50 Ω
(b)