THS4509 Datasheet, PDF (25/30 Pages) Texas Instruments – WIDEBAND, LOW NOISE, LOW DISTORTION FULLY DIFFERENTIAL AMPLIFIER

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Layout Recommendations
It is recommended to follow the layout of the external
components near the amplifier, ground plane con-
struction, and power routing of the EVM as closely as
possible. General guidelines are:
1. Signal routing should be direct and as short as
possible into and out of the opamp circuit.
2. The feedback path should be short and direct
avoiding vias.
3. Ground or power planes should be removed from
directly under the amplifier’s input and output
pins.
4. An output resistor is recommended on each
output, as near to the output pin as possible.
5. Two 10-µF and two 0.1-µF power-supply decoup-
ling capacitors should be placed as near to the
power-supply pins as possible.
6. Two 0.1-µF capacitors should be placed between
the CM input pins and ground. This limits noise
coupled into the pins. One each should be placed
to ground near pin 4 and pin 9.
7. It is recommended to split the ground pane on
layer 2 (L2) as shown below and to use a solid
ground on layer 3 (L3). A single-point connection
should be used between each split section on L2
and L3.
8. A single-point connection to ground on L2 is
recommended for the input termination resistors
R1 and R2. This should be applied to the input
gain resistors if termination is not used.
9. The THS4509 recommended PCB footprint is
shown in Figure 91.
0.144
0.049
Pin 1
0.0095
0.015
0.144
THS4509
SLOS454 – JANUARY 2005
0.012
0.0195 0.0705
0.032
0.010
vias
0.030
0.0245
Top View
Figure 91. QFN Etch and Via Pattern
25