DAC5687IPZPR Datasheet, PDF (53/79 Pages) Texas Instruments – 16-BIT, 500 MSPS 2–8 INTERPOLATING DUAL-CHANNEL DIGITAL-TO-ANALOG CONVERTER (DAC)

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AVDD
R_LOAD
IOUT1
R_LOAD
IOUT2
S(1)
S(1)C
S(2)
DAC5687
SLWS164E – FEBRUARY 2005 – REVISED SEPTEMBER 2006
S(2)C
S(N)
S(N)C
Figure 59. Equivalent Analog Current Output
S0032-01
The DAC5687 can be easily configured to drive a doubly terminated 50-Ω cable using a properly selected RF
transformer. Figure 60 and Figure 61 show the 50-Ω 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 must be
connected to AVDD to enable a dc current flow. Applying a 20-mA full-scale output current would lead to a
0.5-V_PP output for a 1:1 transformer and a 1-V_PP output for a 4:1 transformer. The low dc impedance between the
IOUT1 or IOUT2 and the transformer center tap sets the center of the ac signal at AVDD, so the 1-V_PP output for
the 4:1 transformer results in an output between AVDD + 0.5 V and AVDD – 0.5 V.
AVDD (3.3 V)
50 Ω
IOUT1
1:1
100 Ω
IOUT2
R_LOAD
50 Ω
50 Ω
AVDD (3.3 V)
S0033-01
Figure 60. Driving a Doubly Terminated 50-Ω Cable Using a 1:1 Impedance Ratio Transformer
Copyright © 2005–2006, Texas Instruments Incorporated
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