EVM Basic Functions
1-3
EVM Overview
The REF102 precision reference is powered by V
CC
(15 V) supply through
J1 - 3 or J6 - 1 terminal.
The DAC7731 has a REFEN_ pin to enable the internal reference circuit or to
disable it and select an external reference source. The REFEN_ pin can be
hardware-driven through W2 jumper. Likewise, it can also be software-driven
through J2 - 19 terminal via W2 jumper by shorting pins 1 and 2. The REF
OUT
pin of the DAC7731 must be connected to the REF
IN
pin to use the internal
voltage reference. This can be done through W3 jumper by shorting pins 1 and
2. Shorting pins 2 and 3 of W3 selects the external voltage reference source.
The on-chip reference buffer output is channeled out through V
REF
pin, which
is used to set up the DAC7731 output amplifier into one of three voltage output
modes (refer to the data sheet). V
REF
can also be used to drive other system
components that require external voltage reference.
When applying an external voltage reference through TP1 or J4- 20,
make sure that it does not exceed 10 V maximum. Otherwise, this
can permanently damage the DAC7731, U1, device under test.
1.3
EVM Basic Functions
The DAC7731 EVM is designed primarily as a functional evaluation platform
to test certain functional characteristics of the DAC7731 digital-to-analog
converter. Functional evaluation of the DAC device can be accomplished with
the use of any microprocessor, TI DSP (with SPI capability), or some sort of
a waveform generator.
The headers J2 and P2 are the connectors provided which allow control
signals and data required to interface a host processor or a waveform
generator using a customized cable.
A specific adapter interface card is also available for most of TI’s DSP starter
kits (DSK) and the card model depends on the type of the TI DSP starter kit
used. Specify the DSP with which you are interfacing to ensure acquiring the
right adapter interface card. In addition, an MSP430 microprocessor-based
motherboard platform is available for connection and interface with this EVM,
provided a 5-V level shifter is used for stable operation. The 5-V level shifter
is also available upon request. For more details or information regarding the
adapters mentioned above or the MSP430 motherboard platform, call or email
Texas Instruments. Use email address
datac
o
for fast
response.
The output of the DAC can be monitored via W13. The 6-pin header, W13,
provides different options of the DAC output, but requires the output op amp,
U2, to be configured correctly first for the desired waveform characteristic.
Because of the headroom issue with the op amp, the reference voltage must
be adjusted to prevent the output from clipping. If the internal reference voltage
