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2.3 Onboard ADC Reference
The EVM does not include a provision for driving the reference input of the ADS9110 from an external
source. The reference input signal path is entirely self-contained on the ADS9110EVM and consists of
REF5045, a 4.5-V precision voltage reference. The output of REF5025 is filtered and buffered by a
reference driver formed from two amplifiers: OPA625 and OPA378. This reference driver offers zero-
offset, low-noise and is optimized for 1-LSB voltage regulation under maximum loading conditions at full
device throughput of 2 MSPS. The schematic for the reference driver circuit is shown in
Figure 3 .
Figure 3. Onboard Reference Signal Path
3 Digital Interfaces
As noted in Section 1 , the EVM interfaces with the PHI that, in turn, communicates with the computer over
USB. There are three devices on the EVM with which the PHI communicates: the ADS9110 ADC (over
SPI or multiSPI), the EEPROM (over I
2
C), and the microSD memory card (via the SD/MMC/SDIO bus
protocol). The SD card and EEPROM come pre-programmed with the information required to configure
and initialize the ADS9110EVM-PDK platform. Once the hardware is initialized, the SD card and EEPROM
are no longer used.
3.1 multiSPI
®
for ADC Digital IO
The ADS9110EVM-PDK supports all the interface modes as detailed in the ADS9110 datasheet
(
SBAS629 ). In addition to the standard SPI modes, (with single-, dual- and quad-SDO lanes), the multiSPI
modes support single- and dual-data output rates and the four possible clock source settings as well. The
PHI is capable of operating at a 1.8-V logic level and is directly connected to the digital I/O lines of the
ADC.
8 ADS9110EVM-PDK SBAU249 – October 2015
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