Texas Instruments DAC5687 EVM, User Manual

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4.3 Output Data
4.3.1 Transformer-Coupled Signal Output
Circuit Description
Table 2. Input Connector J13 (Data A Bus) (continued)
Pin Description Pin Description
11 CMOS data bit 10 28 GND
12 GND 29 CMOS data bit 1
13 CMOS data bit 9 30 GND
14 GND 31 CMOS data bit 0 (LSB)
15 CMOS data bit 8 32 GND
16 GND 33
17 CMOS data bit 7 34 GND
Table 3. Input Connector J14 (Data B Bus)
Pin Description Pin Description
1 CMOS data bit 0 (LSB) 18 GND
2 GND 19 CMOS data bit 9
3 CMOS data bit 1 20 GND
4 GND 21 CMOS data bit 10
5 CMOS data bit 2 22 GND
6 GND 23 CMOS data bit 11
7 CMOS data bit 3 24 GND
8 GND 25 CMOS data bit 12
9 CMOS data bit 4 26 GND
10 GND 27 CMOS data bit 13
11 CMOS data bit 5 28 GND
12 GND 29 CMOS data bit 14
13 CMOS data bit 6 30 GND
14 GND 31 CMOS data bit 15 (MSB)
15 CMOS data bit 7 32 GND
16 GND 33
17 CMOS data bit 8 34 GND
The DAC5687 EVM can be configured to drive a doubly terminated 50-
Ω
cable or provide unbuffered
differential outputs.
The factory-set configuration of the demonstration board provides the user with single-ended output
signals at SMA connectors J5 and J19. The DAC5687 outputs are configured to drive a doubly terminated
50-
Ω
cable using a 4:1 impedance ratio transformer with the center tap of the transformers connected to
+3.3 VA as shown in Table 4 . When using a 1:1 impedance ratio transformer, configure the EVM as
shown in Table 4 . The common mode input voltage of T1 and T2 can be adjusted by using the resistor
divider networks. With the board configured to use transformer T5 per Table 4, the DAC outputs will be
summed together and provide 40-mA full-scale output power at SMA connector J11.
Table 4. Transformer Output Configuration
Configuration Components Installed
(1)
Components Not Installed
1:1 Impedance ratio R5 (49.9), R10 (49.9), R19 (49.9), R20 (49.9), R21, R22, R6-R9, R24, R27-R33
transformer R23, R26, C60, C61, T1(1:1), T2 (1:1)
(1)
All component values are per the schematic except where shown in parenthesis.
SLWU017B – APRIL 2005 – Revised March 2007 DAC5687 EVM 23
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