Texas Instruments PSIEVM, User Manual

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PSIEVM Operation
11 SBAU289 – October 2017
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Copyright © 2017, Texas Instruments Incorporated
Precision Signal Injector EVM (PSIEVM)
3.3 AC versus DC Output
The PSIEVM is able to output a sine wave or a DC level. This change is made with the drop-down menu
for
Output Mode .
3.4 Amplitude Setting and Output Enable
The amplitudes selectable in the PSI GUI are available for AC single ended or differential as well as for
DC output, see
Table 5 . Once all PSI GUI parameters have been selected, enabling the output allows for
the selected signal to be produced from the PSIEVM. Disabling the output defaults the PSIEVM output to
ground.
Table 5. Amplitude Range
Output Type Minimum Maximum
AC Single Ended or Differential 0 Vpp 11.88 Vpp
DC Single Ended or Differential 0 V 11.88 V
3.5 Frequency Selection
The eighth-order filter implemented on the PSIEVM and explained in Section 5.4 , is optimized for a 2-kHz
signal. The PSIEVM can create signals at other frequencies to effectively use a signal frequency other
than 2 kHz, the filter must be bypassed by placing JP1 and JP3 into bypass mode. Note that the signal is
not filtered when bypassing the eighth-order onboard filter, and consequently, THD and SNR are
degraded. The PSI GUI allows input of any frequency, up to 20 kHz.
3.6 Typical Performance
Table 6 shows typical performance seen using the PSIEVM with the ADS8900BEVM with full scale
signals.
Table 6. Typical Performance
Measurement Value
SNR 101 dB
THD –123 dB
SNR without filter 63.8 dB
THD without filter –86.3 dB
DC resolution 36 codes = 0.34 mV
4 Examples Using PSIEVM to Drive TI Data Converter EVMs
In this section the PSIEVM is used to drive three different examples of SAR ADC evaluation modules. This
includes both single-ended and differential cases.
4.1 Example of Single-Ended Operation With ADS8881EVM
To explain the single-ended output mode of operation, an example using the ADS8881EVM follows. The
hardware setup is shown in
Table 7 and Figure 10 . First, download the ADS8881EVM GUI to use the
ADC to acquire the PSIEVM output signals. Then, connect the PSIEVM to the ADS8881EVM by having
P2 on the PSIEVM attached to J1 on the ADS8881EVM, also tie JP2 to ground on the ADS8881EVM and
have no jumper installed on JP3. Next, select the output parameters as shown in
Table 8 . Lastly, enable
the output on the PSI GUI and use the ADS8881EVM to acquire the signal. Figure 11 and Figure 12 show
the two GUIs for this test. Table 9 shows the expected results for this test setup.