adc12041 National Semiconductor Corporation, adc12041 Datasheet - Page 26

• Manufacturer Part Number: adc12041
• Description: 12-bit Plus Sign 216 Khz Sampling Analog-to-digital Converter
• Manufacturer: National Semiconductor Corporation

www.national.com
Analog Application Information
When measuring AC input signals, any crosstalk between
analog input lines and the reference lines (ADCIN
should be minimized. Crosstalk is minimized by reducing
any stray capacitance between the lines. This can be done
by increasing the clearance between traces, keeping the
traces as short as possible, shielding traces from each other
by placing them on different sides of the AGND plane, or run-
ning AGND traces between them.
Figure 21 also shows the reference input bypass capacitors.
Here the reference inputs are considered to be differential.
The performance improves by having a 0.1 µF capacitor be-
FIGURE 21. Top View of Printed Circuit Board for a 28-Pin PLCC ADC12041
±
, V
REF
(Continued)
±
)
26
tween the V
similar to that described for the supply pins. When a single
ended reference is used, V
only two capacitors are used between V
µF + 10 µF). It is recommended to directly connect the
AGND side of these capacitors to the V
necting V
rately to the ground planes. This provides a significantly
lower-impedance connection when using surface mount
technology.
REF
REF
− and the ground sides of the capacitors sepa-
+ and V
REF
−, and by bypassing in a manner
REF
− is connected to AGND and
REF
REF
+ and V
− instead of con-
DS012441-45
REF
− (0.1