U2
±
OPA1662
U3
±
OPA1612
8
TH
Order Filter
U1
OPA226
Gain = +2
U8
Audio
DAC
U6
MSP430F5503
U17
VCM
DAC
U18
OPA827
Buffer
U7
THS4131
Fully
Differential
Amplifier
P2
P5
P4
Single Ended
Output
Differential
Output
-
+
Copyright © 2017, Texas Instruments Incorporated
PSIEVM Design Overview
21
SBAU289 – October 2017
Copyright © 2017, Texas Instruments Incorporated
Precision Signal Injector EVM (PSIEVM)
5.3
Connectors for Signal Output
The PSIEVM is designed to be easily interfaced with a TI SAR ADC EVM via a subminiature version A
(SMA) connector. P2, P4, and P5 are SMA connectors that allow analog output connectivity through
coaxial cables.
5.4
Signal Path
The PSIEVM takes user inputs from the GUI and transforms them into a highly-precise output signal. This
process starts with the MSP430F5503 taking the user inputs and sending them to an audio digital-to-
analog converter (DAC). The output of the audio DAC is then driven through a non-inverting topology op
amp with a set gain of 2 volts-per-volt. The resulting signal is then placed through an eighth-order filter
and this is the single-ended output signal. For the differential output, the single-ended output is driven into
a fully differential amplifier.
The offset or common-mode voltage is controlled by a DAC, which takes input from the MSP430 and
produces a voltage that drives into the filter to add single-ended offset and into the fully differential
amplifier to add differential output common mode.
helps visualize the explained signal path.
Figure 19. Signal Path Illustration
5.5
Power Supplies
The USB supply is used to provide power to the analog power rail, digital power rail, positive amplifier
supply, and negative amplifier supply. The power tree is shown in
and in
. External
power supplies are not required but are an available option, see
Table 16. Power Supplies
Power Rail
Voltage
Test Point
USB supply
4.75 V to 5.25 V
V_USB – TP3
Analog 3.3 (AV 3.3)
3.3 V
A3.3 – TP4
Digital 3.3 (DV 3.3)
3.3 V
D3.3 – TP5
Positive supply from switching regulator (POS SUP)
13.5 V
POS – TP1
Negative supply from switching regulator (NEG SUP)
–13.5 V
NEG – TP2
Positive supply from linear regulator (V_12)
12 V
P12 – TP6
Negative supply from linear regulator (VM_12)
–12 V
M12 – TP7
