Texas Instruments ADS8900BEVM-PDK, User Manual, Page: 8 / 39

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8 SBAU269 – October 2016
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ADS8900BEVM-PDK
2.3 Onboard ADC Reference
The EVM does not include a provision for driving the reference input of the ADS8900B from an external
source. The reference input signal path is entirely self-contained on the ADS8900BEVM and consists of
the REF5050, a 5.0-V precision voltage reference. The output of the REF5050 is filtered by a 10-k
Ω and
10-µF low-pass filter. The low-pass filtered output functions as an input to the internal reference buffer of
the ADS8900B ADC. This internal reference driver offers zero-offset, low-noise, and is optimized for a 1-
LSB voltage regulation under maximum loading conditions at full device throughput of 1 MSPS.
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 two devices on the EVM with which the PHI communicates: the ADS8900B ADC (over
SPI or multiSPI) and the EEPROM (over I
2
C). The EEPROM comes pre-programmed with the information
required to configure and initialize the ADS8900BEVM-PDK platform. Once the hardware is initialized, the
EEPROM is no longer used.
3.1 multiSPI
®
for ADC Digital IO
The ADS8900BEVM-PDK supports all the interface modes as detailed in the ADS8900B datasheet ( TBD ).
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 3.3-V logic level and is directly connected to the digital I/O lines of the ADC.