Datasheet

ADC12048
www.ti.com SNAS105B –APRIL 2000–REVISED MARCH 2013
Figure 49. Top View of Printed Circuit Board for a 44-Pin PLCC ADC12048
When measuring AC input signals, any crosstalk between analog input/output lines and the reference lines
(CH0–CH7, MUXOUT±, ADC IN±, V
REF
±) 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
running AGND traces between them.
Figure 49 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 between the V
REF
+ and V
REF
−, and by
bypassing in a manner similar to that described for the supply pins. When a single ended reference is used,
V
REF
− is connected to AGND and only two capacitors are used between V
REF
+ and V
REF
− (0.1 μF + 10 μF). It is
recommended to directly connect the AGND side of these capacitors to the V
REF
− instead of connecting V
REF
−
and the ground sides of the capacitors separately to the ground planes. This provides a significantly lower-
impedance connection when using surface mount technology.
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