Texas Instruments DAC8881, Руководство пользователя, Страница: 16 / 25

2
1 7
8
13
14
2
1 7
8
13
14 4
3
2
1 13
14 6
5
2
1 13
14 8
7
2
1 13
14 10
9
2
1 11
12 8
7
2
1 13
14 8
7
2 6
1 5 3
4
2 6
1 5 3
4
2 6
1 5 3
4
Using the DAC8881EVM with DXP
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Table 7. Jumper Setting Functions (continued)
Jumper
Reference Function
Setting
Connects the inverting input of U2 to the R12 gain resistor for DAC8881 2x gain of operation.
W12
Disconnects the inverting input of U2 from the R12 gain resistor to allow another output mode of
configuration.
If jumper is installed on pins 1 and 2, the LDAC signal of the DAC8881 is tied to ground for
synchronous DAC update operation.
If jumper is installed on pins 3 and 4, the RSTSEL pin of the DAC8881 is tied to ground so the
DAC output is at 0V upon power up or a reset to the device is issued.
If jumper is installed on pins 5 and 6, the GAIN pin of the DAC8881 is tied to IOV
DD
so that the
DAC output is set with a gain of two output.
If jumper is installed on pins 7 and 8, the USB/BTC pin of the DAC8881 is tied to ground so that
J1
the DAC input data format is set for twos complement format.
If jumper is installed on pins 9 and 10, the RST pin of the DAC8881 is tied to ground so that the
DAC is forced into hardware reset mode.
If jumper is installed on pins 11 and 12, the PDN pin of the DAC8881 is tied to IOV
DD
so that the
DAC is forced into power-down status.
If jumper is installed on pins 13 and 14, the SDOSEL pin of the DAC8881 is tied to ground so
that the DAC device can be operated in daisy-chain mode.
DAC8881 IOV
DD
is powered with +5VD.
J3 DAC8881 IOV
DD
is powered with +1.8VD.
DAC8881 IOV
DD
is powered with +3.3VD.
Legend: Indicates the corresponding pins that are shorted or closed.
3.6 Schematics
The DAC8881 evaluation module schematic appears on the following page.
4 Using the DAC8881EVM with DXP
The DAC8881EVM is compatible with the DAC eXerciser Program (DXP) from Texas Instruments. DXP is
a tool that can generate the necessary control signals required to output various signals and waveforms
from the DAC8881EVM. The DAC8881EVM-PDK kit combines the DAC8881EVM board with the DSP
based modular motherboard MMB0. The kit includes the DXP software for evaluation using any available
USB port on a Windows XP based computer.
DXP is a program for controlling the digital input signals such as the clock, LDAC, /CS and SDI. Wave
tables are built into the DSP software to allow Sine, Ramp, Triangle, and Square wave signals to be
generated by the DAC8881. Straight DC outputs can also be obtained.
The DAC8881EVM-PDK is controlled by loading a DAC EVM configuration into the MMB0. For complete
information about installing and configuring DXP, see the DXP User's Guide (
SBAU146 ), available for
download from the TI web site.
16 DAC8881 Evaluation Module SLAU257A – September 2008 – Revised November 2009
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