Texas Instruments ADS7881, User Manual, Page: 2 / 23

1 Introduction
The ADS78x1EVM showcases the 12-bit, 4-MSPS (ADS7881) and 14-bit, 3-MSPS (ADS7891) ADCs. The
ADS7881 and ADS7891 devices include a capacitor-based successive-approximation register (SAR) ADC with
inherent sample and hold. These devices offer either a 12-bit or 14-bit parallel interface. Both devices offer byte
mode operation that enables easy interface with 8-bit processors. They also have a pseudo-differential input
stage and a 2.5-V internal reference.
This evaluation module serves as a reference design and a low-cost method to test these converters in the end
application. The following sections describe the pin outs of the various analog, power, and digital connectors and
power requirements.
Table 1-1 lists documents related to the ADS78x1EVM.
Table 1-1. Related Documentation from Texas Instruments
Data Sheets Literature Number
ADS7881 SLAS400
ADS7891 SLAS410
ADS8411 SLAS369
THS4031 SLOS224
OPA132 SBOS054
REF1004-2.5 SBVS032
SN74AHC138 SCLS258
SN74AHC245 SCLS230
SN74AHC1G04 SCLS318
1.1 Features
The ADS78x1EVM includes the following features:
• Full-featured evaluation board for the high-speed, SAR-type ADS7881(12-bit, 4-MSPS) or ADS7891(14-bit,
3-MSPS) single-channel, parallel interface ADCs
• Onboard signal conditioning
• Onboard reference
• Input and output digital buffers
• Onboard decoding for stacking multiple EVMs
1.2 Analog Interface
The ADS7881 and ADS7891 ADCs have both a positive and negative analog input pin. The negative input pin,
which has a range of –200 mV up to 200 mV is shorted on the board. A signal for the positive input pin can be
applied at connector P1, pin 2 (as shown in
Table 1-2 ) or at the center pin of the SMA connector J2.
Table 1-2. Analog Input Connector
Connector.Pin#
(1)
Signal Description
P1.2 +IN Noninverting input channel
P1.4 Reserved —
P1.6 Reserved —
P1.8 Reserved —
P1.10 Reserved —
P1.12 Reserved —
P1.14 Reserved —
P1.16 Reserved —
P1.18 Reserved —
P1.20 REF+ External reference input
(1) All odd-numbered pins of P1 are tied to AGND.
Introduction www.ti.com
2 ADS7881EVM, ADS7891EVM Evaluation Module SLAU150A – DECEMBER 2004 – REVISED OCTOBER 2021
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