Datasheet

1 EVM Overview
1.1 Features
2 Introduction
3 Analog Interface
EVM Overview www.ti.com
• Full-featured evaluation board for the high-speed, 18-bit ADS8482 and ADS8484 1-MSPS/1.25-MSPS,
single-channel, parallel interface, SAR-type analog-to-digital converters
• Onboard signal conditioning
• Onboard reference
• Input and output digital buffers
• Onboard decoding for stacking multiple EVMs
The ADS8482 is an 18-bit, 1-MSPS analog-to-digital converter (ADC) with an internal 4.096-V reference
and a pseudo-bipolar, fully differential input. The ADS8484 is an 18-bit, 1.25-MSPS version of the same
core design. These devices are capacitor-based, successive approximation register (SAR) converters with
an inherent sample-and-hold stage. The ADS848x has 8-bit, 16-bit, and 18-bit parallel interface bus
options, allowing a variety of processors to interface easily.
The ADS848xEVM is an evaluation and demonstration platform for the ADS848x ADC. The EVM board is
a flexible design that allows the user to choose among many different analog signal conditioning,
reference, and interface modes.
The ADC accepts a pseudo-bipolar differential input. A pseudo-bipolar differential signal is a fully
differential signal that has a common-mode voltage such that the voltage on each input is always equal to
or greater than 0 V. The common-mode voltage should be half the reference voltage. The peak-to-peak
amplitude on each input leg can be as large as the reference voltage.
The positive leg of the input signal can be applied at connector P1, pin 2 (shown in Table 1 ) or via the
center pin of SMA connector J1. Likewise, the negative input signal can be applied at P1, pin 1 or via the
center pin of SMA connector J2.
Table 1. Analog Input Connector
Description Signal Name Connector Pin No. Signal Name Description
Not connected – P1.1 P1.2 + Noninverting input channel
Reserved N/A P1.3 P1.4 N/A Reserved
Reserved N/A P1.5 P1.6 N/A Reserved
Reserved N/A P1.7 P1.8 N/A Reserved
Reserved N/A P1.9 P1.10 N/A Reserved
Pin tied to ground AGND P1.11 P1.12 N/A Reserved
Pin tied to ground AGND P1.13 P1.14 N/A Reserved
Reserved N/A P1.15 P1.16 N/A Reserved
Pin tied to ground AGND P1.17 P1.18 N/A Reserved
Pin tied to ground AGND P1.19 P1.20 REF+ External reference input
2 ADS848xEVM SLAU186A – August 2006 – Revised September 2008
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