XR620A Datasheet, PDF (13/15 Pages) Exar Corporation – Instrumentation Amplifier

Grounding
The output voltage of the XR620A is developed with respect
to the potential on the reference terminal (pin 8). Simply
tie the REF pin to the appropriate “local ground” to resolve
many grounding problems.
To isolate low level analog signals from a noisy digital
environment, many data acquisition components have
separate analog and digital ground pins. Use separate
ground lines (analog and digital) to minimize current flow
from sensitive areas to system ground. These ground
returns must be tied together at some point, usually best at
the ADC.
Layout Considerations
General layout and supply bypassing play major roles in
high frequency performance. Exar has evaluation boards to
use as a guide for high frequency layout and as an aid in
device testing and characterization. Follow the steps below
as a basis for high frequency layout:
■■ Include 6.8µF and 0.1µF ceramic capacitors for power supply
decoupling
■■ Place the 6.8µF capacitor within 0.75 inches of the power pin
■■ Place the 0.1µF capacitor within 0.1 inches of the power pin
■■ Remove the ground plane under and around the part,
especially near the input and output pins to reduce parasitic
capacitance
■■ Minimize all trace lengths to reduce series inductances
Refer to the evaluation board layouts below for more
information.
Evaluation Board Information
The following evaluation boards are available to aid in the
testing and layout of these devices:
Evaluation Board #
CEB024
Products
XR620A in SOIC-8
Evaluation Board Schematics
Evaluation board schematics and layouts are shown in
Figures 6-8. These evaluation boards are built for dual-
supply operation. Follow these steps to use the board in a
single-supply application:
1. Short -V_S to ground.
2. Use C3 and C4, if the -V_S pin of the amplifier is not
directly connected to the ground plane.
© 2013-2015 Exar Corporation
13 / 15
XR620A
Figure 6. CEB024 Schematic
Figure 7. CEB024 Top View
Figure 8. CEB024 Bottom View
exar.com/XR620A
Rev 1B