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2.2 Reference
3 Digital Interface
Digital Interface
The EVM allows users to select from three reference sources. The ADS8402/ADS8406/ADS8412EVM
provides an onboard 4.096-V reference, U3. The EVM also has the provision for users to supply a
reference voltage via connector P1 pin 20. The user reference voltage and onboard reference voltages
can be filtered by installing amplifier U1. The ADS8402, ADS8406, and ADS8412 analog-to-digital
converters have a integrated onboard reference buffer; therefore, it is not necessary to buffer the voltage
externally. The reference buffer circuit on the EVM is not populated with an amplifier for this reason. The
EVM comes installed with on-chip internal reference tied directly to the reference pin of the converter. See
Section 8 for a full schematic.
Table 2. Solder Short Jumper Setting
(1)
Jumper Settings
Reference
Description
Designator
1-2 2-3
On-chip internal reference applied to A/D reference pin Installed
(2)
SJP2
Apply reference voltage from external source Installed
SJP3 Apply voltage to amplifier, U2, common-mode voltage pin Installed
(2)
N/A
Buffer onboard reference, REF3040 Installed Not installed
SJP4
Buffer user reference voltage applied at P1 pin 20 Not installed installed
Select REF3040 for reference voltage Installed Not installed
SJP5
Select buffered reference voltage Not Installed Installed
(1) Designator SJP1 is not used on the EVM.
(2) Factory installed
The ADS8402/ADS8406/ADS8412 EVM is designed for easy interfacing to multiple platforms. Samtec part
numbers SSW-110-22-F-D-VS-K and TSM-110-01-T-DV-P provide a convenient dual-row header/socket
combination at P2 and P3. Consult Samtec at www.samtec.com or 1-800-SAMTEC-9 for a variety of
mating connector options.
Table 3. Pinout for Parallel Control Connector P2
(1)
Connector.Pin Signal Description
P2.1 DC_CS Daughtercard board-select pin
P2.3
P2.5
P2.7 A0 Address line from processor
P2.9 A1 Address line from processor
P2.11 A2 Address line from processor
P2.13
P2.15
P2.17
P2.19 INTc Set jumper to select BUSY or inverted signal to be applied to this pin.
(1) All even numbered pins of P2 are tied to DGND.
4 ADS8402/ADS8406/ADS8412 EVM User's Guide SLAU126A – December 2003 – Revised September 2004