For best operational performance of the device,
use good printed circuit board (PCB) layout practices, including:
- Noise can
propagate into analog circuitry through the power
pins of the circuit as a whole and op amp itself.
Bypass capacitors are used to reduce the coupled
noise by providing low-impedance power sources local
to the analog circuitry.
- Connect low-ESR, 0.1-µF ceramic bypass capacitors
between each supply pin and ground, placed as
close to the device as possible. A single bypass
capacitor from V+ to ground is applicable for
single-supply applications.
- Separate
grounding for analog and digital portions of
circuitry is one of the simplest and most-effective
methods of noise suppression. One or more layers on
multilayer PCBs are usually devoted to ground
planes. A ground plane helps distribute heat and
reduces EMI noise pickup. Make sure to physically
separate digital and analog grounds paying attention
to the flow of the ground current. For more detailed
information refer to the Circuit Board Layout
Techniques application report.
- In order
to reduce parasitic coupling, run the input traces
as far away from the supply or output traces as
possible. If these traces cannot be kept separate,
crossing the sensitive trace perpendicular is much
better as opposed to in parallel with the noisy
trace.
- Place the
external components as close to the device as
possible. As shown in Figure 10-1, keeping RF and RG close to the inverting input
minimizes parasitic capacitance.
- Keep the
length of input traces as short as possible. Always
remember that the input traces are the most
sensitive part of the circuit.
- Consider
a driven, low-impedance guard ring around the
critical traces. A guard ring can significantly
reduce leakage currents from nearby traces that are
at different potentials.
- Cleaning
the PCB following board assembly is recommended for
best performance.
- Any
precision integrated circuit may experience
performance shifts due to moisture ingress into the
plastic package. Following any aqueous PCB cleaning
process, baking the PCB assembly is recommended to
remove moisture introduced into the device packaging
during the cleaning process. A low-temperature,
post-cleaning bake at 85°C for 30 minutes is
sufficient for most circumstances.