Reference Voltage Generation - Analog Devices ADSP-21992 EZ-KIT LITE System Manual

System Architecture

Reference Voltage Generation

The ADSP-21992 EZ-KIT Lite board contains an external voltage refer-
ence, the LM4140-1.0 (
ADSP-21992 EZ-KIT Lite board can be configured to operate from the
internal (ADSP-21992 generated) or the external voltage reference. Two
jumpers control the selection of the internal or external voltage reference.
Jumper ties the
JP3
els. Connecting
reference operation. In this mode, the ADSP-21992 accepts an input volt-
age reference at the
To connect the external voltage reference to the ADSP-21992 on the eval-
uation board, close the
reference from the LM4140-1.0 to the
signal, which is buffered using an operational amplifier OP193 (
level-shifts the applied analog input signals on the analog inputs connec-
tor, , (as well as being connected to the
P4
sample-and-hold amplifiers).
To operate with the internally derived voltage reference of the
ADSP-21992, tie the
to AGND. Additionally, leave jumper
vides a 1V reference at the
and
ASHAN BSHAN
level-shifting circuitry.
See "Voltage Reference Selection Jumpers (JP3, JP4)" on page 3-14
more information.
3-6
), which provides a precise 1.024V output. The
U3
pin of the ADSP-21992 to the
SENSE
to (
SENSE AVDD JP3
pin.
VREF
jumper. This connects the external voltage
JP4
jumper in position 1-2 to connect the
JP3
pin that is buffered and applied to the
VREF
inputs. The buffered
ADSP-21992 EZ-KIT Lite Evaluation System Manual
in position 2-3) selects external voltage
pin of the ADSP-21992. The
VREF
and
ASHAN BSHAN
open. The ADSP-21992 pro-
JP4
signal is also used in the
VREF
or lev-
AVDD GND
),
A11
inputs to the
pin
SENSE
for