SLVUDF8 EVM User's guide

SLVUDF8 November 2025

2.6 Modifications

For flexibility, the EVM provides optional capacitors C4 and C14. These capacitors are in parallel with the PGA854 output-stage internal-feedback resistors (6.67kΩ) to implement noise filtering. To implement noise filtering, establish a frequency of interest (f_oi) in the application and calculate the feedback capacitor. In an example where the f_oi is 1kHz, the capacitor populated on C4 and C14 is 2.2nF (C0G/NP0) capacitor.

Equation 4.

C_{4} a n d C_{14} = \frac{1}{2 π \times 6.67 k Ω \times 10 \times f_{o i}} = \frac{1}{2 π \times 6.67 k Ω \times 10 \times 1 k H z} = 2.39 n F ≅ 2.2 n F

In addition, the evaluation board provides footprints R6, R10, C9, C5, and C12 for optional input low-pass filters, and footprints for load resistors R7 and R11.

The common-mode capacitors (C5 and C12) need to be equal to one another, and the input series resistors (R6 and R10) need to be equal to one another. The differential capacitor (C9) needs to be ten times larger than the common-mode capacitors.

Equation 5.

f_{C M} = \frac{1}{2 π \times R_{I N} \times C_{C M}} = \frac{1}{2 π \times R 6 \times C 5}

Equation 6.

f_{D i f f} = \frac{1}{2 π \times 2 R_{I N} \times (C_{D I F F} + \frac{C_{C M}}{2})} = \frac{1}{4 π \times R 6 \times (C 9 + \frac{C 5}{2})}

These additional component footprints in the layout allow the user to customize the evaluation circuit. For a full schematic of the PGA854EVM, see Figure 3-6.