8.4 Layout

8.4.1 Layout Guidelines

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 DA_IN+ and DA_IN– pins potentially causes dc offset errors 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.

PGA848

SBOSAN4A – AUGUST 2025 – REVISED DECEMBER 2025

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