Support apparatus and design support method

A design support method of supporting design of a printed circuit board on which a device and a switching power supply, which supplies power to the device, are mounted, comprising:

• calculating, based on design information of the printed circuit board including capacitor information indicative of characteristics of at least one decoupling capacitor, a first impedance between a power plane and a ground plane in the printed circuit board at an ON time of a high-side transistor in the switching power supply, and a second impedance between the power plane and the ground plane at an ON time of a low-side transistor in the switching power supply;
• determining one of the first impedance, the second impedance and a third impedance in an intermediate range between the first impedance and the second impedance to be an impedance between the power plane and the ground plane, based on ON-time information indicative of a ratio of an ON period of the high-side transistor to a switching cycle of the switching power supply in an operation period of the device;
• and
• evaluating the capacitor information by comparing the determined impedance and a target impedance.

An apparatus comprising:

• a calculation module configured to calculate, based on design information of a printed circuit board including capacitor information indicative of characteristics of a decoupling capacitor, a first impedance between a power plane and a ground plane in the printed circuit board at an ON time of a high-side transistor in a switching power supply, and a second impedance between the power plane and the ground plane at an ON time of a low-side transistor in the switching power supply;
• a determination module configured to determine one of impedances falling within a range between the first impedance and the second impedance to be an impedance between the power plane and the ground plane, based on ON-time information indicative of a ratio of an ON period of the high-side transistor to a switching cycle of the switching power supply in an operation period of a device on the printed circuit board;
• and
• an evaluation module configured to evaluate the capacitor information based on the determined impedance.