SLLSFD6A May 2020 – March 2021 THVD8000
PRODUCTION DATA
Capacitor selection is easier than inductor selection, primarily because capacitance impedance is important to allow higher frequency signals through. However, the capacitor ratings for voltage must be carefully selected to meet the application requirements. Special considerations for hot plug nodes should be made to ensure that voltage transients during hot plugging do not exceed the absolute maximum values. See Section 6.1.
The number of nodes on the bus does not play into the capacitance calculation. The impedance of a capacitor is shown in Equation 4.
Maintaining Z ≤ 5 Ω keeps the impedance low enough at the carrier frequency to allow data to pass through. If the equation is rearranged to calculate C, the result is shown in Equation 5.
If the previous example of a 1 MHz carrier frequency is used, then a minimum capacitance value of about 32 nF. For a quick reference, refer to Figure 9-3.