POWER SUPPLY FILTER AND ELECTRONIC CIRCUITRY INCLUDING THE SAME
A power supply filter includes a first filter circuit and a second filter circuit connected in parallel with each other across supply voltage input terminals. The first filter circuit has such a low-pass characteristic that a gain of the first filter circuit is higher than that of the second filter circuit in a first band which is a low band. The second filter circuit includes a serially-inserted resistive element and has such a high-pass characteristic that the gain of the second filter circuit is higher than that of the first filter circuit in a second band which is a high band.
1 . A power supply filter comprising:
a first filter circuit and a second filter circuit connected in parallel with each other across supply voltage input terminals, wherein
the first filter circuit has such a low-pass characteristic that a gain of the first filter circuit is higher than that of the second filter circuit in a first band which is a low band, and
the second filter circuit includes a serially-inserted resistive element and has such a high-pass characteristic that the gain of the second filter circuit is higher than that of the first filter circuit in a second band which is a high band.
2 . The power supply filter according to claim 1 , wherein a resistance value of the resistive element is not lower than 0.1Ω.
3 . The power supply filter according to claim 2 , wherein the resistance value of the resistive element is not lower than 0.5Ω and not higher than 1Ω.
4 . The power supply filter according to claim 1 , wherein
the first filter circuit is composed of a first capacitor,
the second filter circuit is composed of a second capacitor and the resistive element which are connected in series, and
a capacitance value of the first capacitor is higher than a capacitance value of the second capacitor.
5 . The power supply filter according to claim 4 , wherein
the capacitance value of the first capacitor is within a range of 10 μF to 100 μF, and
the capacitance value of the second capacitor is within a range of 0.01 μF to 0.1 μF.
6 . The power supply filter according to claim 4 , wherein the second filter circuit is an ESR (Equivalent Series Resistance) capacitor having a capacitive element as the second capacitor and an equivalent series resistance as the resistive element.
7 . Electronic circuitry comprising:
the power supply filter according to claim 1 ; and
a circuit configured to switch a supply voltage inputted via the power supply filter.