Texas Instruments ADS8371EVM, Руководство пользователя, Страница: 13 / 33

Reference
2-3 Analog Interface
2.2 Reference
The ADS8371EVM allows users to select from two reference sources:
-
an onboard (REF1004−2.5)
-
a user supplied reference voltage via P1 pin 20
Both the user supplied reference and the onboard reference voltage can be
amplified and filtered using reference amplifier, U2. The ADS8371EVM ships
with the reference amplifier, U2, set for a gain of 1.6 V. The onboard reference
(U10) is a 2.5-V reference. The user has the option of applying it directly to the
converter, or routing the voltage through the reference amplifier. The
ADS8371 has a onboard reference buffer, so it is not necessary to buffer the
reference voltage being connecting it to the converter. Also, keep in mind that
wiring the voltage reference through the amplifier gains the 2.5-V reference up
to 4.096 V.
The ADS8371EVM ships with 4.096 V connected to the reference pin of the
converter. See Chapter 6 for a full schematic and Table 2−2 for jumper
settings.
Table 2−2. Solder Short Jumper Setting
Reference
Jumper Setting
Reference
Designator
Description
1−2 2−3
SJP1 Apply offset voltage to A/D buffer Installed
†
N/A
Set amplifier U1 negative supply to ground
SJP2 Set amplifier U1 negative supply to −V
CC
Installed
†
Set amplifier U2 negative supply to ground
SJP3 Set amplifier U2 negative supply to −V
CC
Installed
†
Select internal reference source N/A
SJP4
Select external reference voltage Installed
†
Select onboard reference source Installed
†
SJP5
Select buffered reference source
Select onboard reference source Installed
†
SJP6
Buffer user supplied reference voltage
SJP7 Short (−)IN pin to ground Installed
†
N/A
†
Factory-set condition