Factory Default Setting
3-2
3.1
Factory Default Setting
The EVM board is set as default from the factory to the configuration below to
operate in bipolar mode through U2.
Table 3 - 1. Factory Default Jumper Setting
Reference
Jumper Position
Function
W1
1 - 2
V
REF(L)
tied to AGND
W2
1 - 2
Adjustable onboard V
REF(H)
is supplied by U3.
W3
1 - 2
Negative supply rail of U2 is tied to - 15 V.
W4
1 - 2
Positive supply rail of U2 is tied to 15 V.
W5
3 - 4
DAC output signal is directed to J5 and J4-2 output terminals.
W6
Close
Midscale for bipolar operation is set to V
REF(H)
.
W7
Open
U2 is set for 2x gain for bipolar mode of operation.
W8
Close
AGND and DGND are tied together.
3.2
Host Processor Operation
The host processor drives the DAC, so the DAC’s proper operation depends
on the successful configuration between the host processor and the EVM
board, and of course a properly written code to run the DAC.
A custom cable can be made specific to the host interface platform. The EVM
allows interface to the host processor through J2 and J3 header connectors
for control signals, and J1 header connector for the data input. The output can
be monitored through the J5 BNC connector (if installed) or J4 header
connector. An interface adapter card is also available for specific DSP starter
kits as mentioned in Chapter 1.
The EVM incorporates four different options for the DAC output through an
external operational amplifier, U2. This requires some jumper setting
configuration, particularly around the op-amp (U2) circuitry, and other required
equipment. Each option is discussed individually.
The raw output of the DAC can be probed through W5 pin 2 so that it can be
compared with the output of U2 if necessary. The output terminals J5 and J4-2
can be used to monitor the raw output of the DAC by shorting pins 1 and 2 of
W5.
3.2.1
Unity Gain Output
The buffered output should closely match the raw output of the DAC with some
slight distortion because of the feedback resistor and capacitor. The user can
tailor the feedback circuit to closely match their desired wave shape by
desoldering R7 and C11 and replacing it with the desired values. You can also
simply get rid of R7 and C11 altogether and just solder a 0
Ω
resistor in
replacement of R7, if desired.
Table 3 - 2 shows the jumper setting relating to the unity gain configuration of
the output buffer.