For the best output and input voltage filtering, X5R or X7R ceramic capacitors are recommended. The input bulk capacitor minimizes input voltage ripple, suppresses input voltage spikes, and provides a stable system rail for the device. A 10-μF or larger input capacitor is recommended. Having two in parallel further improves the input voltage ripple filtering, minimizing noise coupling into adjacent circuits. The voltage rating of the cap must also be taken into consideration, and must provide the required 5-μF minimum effective capacitance after DC bias derating.
In addition to the bulk input cap, a smaller cap must be placed directly from the VIN pin to the PGND pin to minimize input loop parasitic inductance, thereby minimizing the high frequency noise of the device. The input cap placement affects the output noise, so care needs to be taken in placing both the bulk cap and bypass caps as shown in Section 10.2. Table 8-7 lists recommended input capacitors.
|INPUT CAP TYPE||CAPACITOR VALUE||MANUFACTURER||VOLTAGE RATING (V)||PACKAGE SIZE|
|Bulk Cap||10 μF, X7S||TDK C2012X7S1E106K125AC||25||0805|
|Bypass Cap||2.2 nF, X7R||Murata GRM155R71E222KA01D||25||0402|