Attention to good layout practices is always recommended. For best operational performance of the device, use good PCB layout practices, including:
- To avoid converting common-mode signals into
differential signals and thermal electromotive forces (EMFs), verify both input paths
are symmetrical and well-matched for source impedance and capacitance.
- Noise potentially propagates into analog
circuitry through the power pins of the device and of the circuit as a whole. Bypass
capacitors reduce the coupled noise by providing low-impedance power sources local to
the analog circuitry.
- Connect low-ESR, 0.1µF ceramic
bypass capacitors between each supply pin and ground, placed as close as possible to
the device. A single bypass capacitor from V+ to ground is applicable for
single-supply applications.
- To reduce parasitic coupling, run the input
traces as far away as possible from the supply or output traces. If these traces cannot
be kept separate, crossing the sensitive trace perpendicular is much better than in
parallel with the noisy trace.
- Leakage on the FDA_IN+ and FDA_IN– pins potentially causes a dc offset error
in the output voltages. Additionally, excessive parasitic capacitance at these pins
potentially results in decreased phase margin and affects the stability of the output
stage. If these pins are not used to implement deliberate capacitive feedback, follow
best practices to minimize leakage and parasitic capacitance.
- Follow best practices to minimize leakage and
parasitic capacitance, which includes implementing keep-out areas in any ground
planes located immediately below the input pins.
- Minimize the number of thermal junctions. If possible, route the signal path
using a single layer without vias.
- Keep sufficient distance from major thermal
energy sources (circuits with high power dissipation). If not possible, place the
device so that the thermal energy source effects on both sides of the differential
signal path are evenly matched.
- Keep the traces as short as possible.