Datasheet

VCOM, REF(-) and REF(+) Options
3-3
Analog Outputs
3.3 VCOM, REF(-) and REF(+) Options
Signals VCOM, REF( - ) and REF(+) provide additional flexibility to certain
ADC evaluation modules. In some cases, ADCs that provide a reference
voltage output may have that voltage routed to the analog I/O connector for
use as a biasing voltage for the amplifiers on the signal condition board. The
REF( - ) and REF(+) signals can also be routed to certain ADC and DAC boards
in order to provide the data converter with a user definable reference input.
Details for the specific use of these signals should be found in the users guide
for the individual data converter evaluation module.
External reference voltages may be applied to three-terminal screw jack (J8).
REF (+) is applied to pin 1, REF ( - ) to pin 3. The external reference voltages
are grounded at J8, pin 2. Test points 2, 4, and 5 are used to monitor the
external reference.
By default, the amplifiers on the signal conditioning board are biased to 2.5 V
by means of an on-board voltage regulator (U5). W9 selects the on-board
regulator (position 1-2) or the external VCOM voltage applied to J7 (position
2-3). To remove the bias voltage and ground the inverting inputs of the
amplifiers, W9 is placed in position 2-3 with an additional shut jumper placed
on J7, pins 15-17.
3.3.1 Installation Example
Figure 3-1 shows an installation example using two signal conditioning
boards on the 5-6K interface card. The C2000 and HPA449 interface cards
have the same connector arrangement which allows the signal conditioning
board to be used across all three platforms.
Figure 3-1. Signal Conditiioning Board Installation on 5-6K Interfaces