Texas Instruments ADS8370EVM, User Manual, Page: 3 / 16

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_
+
THS4031
0.1 F
1 F
1 F
0.1 F
−V
CC
+V
CC
604
604
V
IN
12
6800 pF
1 F
100
10 k
4.096 V
IN+
IN−
2.2 Reference Voltage
Analog Interface
Figure 1. Input Buffer Circuit
The ADS8380EVM allows the designer to select internal, onboard, or user-supplied reference-voltage
sources. The internal reference is a 4.096-V reference voltage generated by the ADS8380 on pin 9. The
onboard reference can be either a REF3040 (U1) or REF1004-2.5 (U13). The EVM ships with the
REF1004-2.5 installed. The reference amplifier, U3, is set for a gain of 1.6, enabling it to take a 2.5-V
input and output 4.1 V for use with the converter, or as part of the dc offset voltage circuit for the input
buffer (U4). The user-supplied reference voltage is applied to connector P1, pin 20 and can be routed
through the reference buffer and filtered, if desired. The EVM allows a number of configurations. See
Table 1 for jumper settings or the full schematic in Section 9 for more information. The common SOIC
footprint of U13 allows users to evaluate this converter with various reference ICs.
The ADS8380EVM ships with the internal reference tied directly to the reference pin of the converter.
SLAU146 – December 2004 3 ADS8380EVM