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EVM Operation
Supply voltages of +2.7 Vdc to +5.5 Vdc for the V
with one of the previously mentioned interface boards, J3 provides connection to the common power bus
described in the 5-6K Interface Board EVM User's Guide (SLAU104).
Table 4
shows the pinout of connector J3.
4.1
Stand-Alone Operation
When used as a stand-alone EVM, the analog power can be applied to J3 pins 3 and 4, referenced to J3
pin 6. Digital power can be applied to J3 pin 10, referenced to J3 pin 5. Optimal performance of the EVM
requires a clean, well-regulated power source.
The DAC7811 has a V
If using an external reference source, keep the reference voltage to a level
less than or equal to the maximum limits described in the Electrical
Characteristics table of the DAC7811 data sheet.
4.2
Reference Voltage
The DAC7811 can be configured to use the onboard reference/buffer circuits (U1, U3, and U4) or an
external reference applied to W3, pin 2 (completely remove shunt jumper). Jumper W3 controls the
reference source. In the factory default position (shunt on W3 pins 1-2), a –10-V reference is applied to
the DAC7811 (U5). Moving the shunt at W3 to pins 2-3 applies a positive 10-V reference to the DAC7811.
The DAC7811, as a 2-quadrant multiplying DAC, can be used to generate a unipolar output. The polarity
of the full-scale output IOUT is the inverse of the input reference voltage at VREF. Some applications
require full 4-quadrant multiplying capabilities or bipolar output swing. As shown in the schematic, the
second half of U2 is added as a summing amplifier and has a gain of 2X that widens the output span to 20
V. A 4-quadrant multiplying circuit is implemented by using a 10-V offset from the reference voltage to bias
U4.
5
EVM Operation
5.1
Analog Output
The analog output is applied to J1 pins 4 to 14 (even) by the application of a shunt jumper on W2. The
factory default is to apply the voltage output from U2 to J1.4. The analog output range depends on the
configuration of the EVM and the reference applied to the DAC7811. See Sections 3 and 4.2 of this user's
guide and the DAC7811 data sheet (SBAS337) to determine the maximum analog output range.
4
DAC7811EVM
Table 4. Pinout of J3
Signal
Pin Number
Unused
1
+5VA
3
DGND
5
Unused
7
Unused
9
power source requirement of +2.7 Vdc to +5.5 Vdc.
DD
supply to the DAC7811 are also required. When used
DD
2
Unused
4
6
8
Unused
10
CAUTION
www.ti.com
Signal
–5VA
AGND
+5VD
SLAU163 – September 2005
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