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ADS8028EVM Hardware Details

3.1 Analog Inputs

The ADS8028 provides eight single-ended input channels plus an internal temperature sensor. The eight

analog input channels to the ADS8028 (AIN0 to AIN7) are connected to J-ANALOG on the ADS8028EVM.

Channels 0 and 1 are buffered converter inputs. The OPA836 is configured as a unity-gain buffer on these

channels. Channels 2 to 7 connect directly to the converter with an option to add an RC filter before the

converter input. Figure 4 shows the EVM schematic portion of the analog inputs. All discrete resistors and

capacitors shown in Figure 4 are size 0603 and can be modified to adjust circuit gain and filtering. Note

that not all components shown in Figure 4 are installed and have values "NI" (not installed).

Optionally, the user can add an SMA connector at J-SMA and use an SMA input for channels 0 and 1 if

an SMA connection is more convenient. RS0 and RS1 resistors select the SMA input channel. If the SMA

input has a 50-Ω source impedance, R10 and other input resistors can be modified for impedance

matching, otherwise they can provide signal attenuation and input current limiting.

Figure 4. Analog Input Header Schematic

NOTE: All odd pins on J-ANALOG connect to GND. Therefore, all analog input connections can be

easily made across even and odd pin numbers (The channel 0 input connects to J-

ANALOG.1-2, channel 1 input connects to J-ANALOG.3-4, etc.).

SBAU198–April 2012 ADS8028EVM-PDK

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