MGC3140 datasheet(24/49 Pages) MICROCHIP

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These are typical operating voltages.

It is important that the low-ESR capacitor is placed as close as possible to the VCAP pin.

The typical voltage on the VCAP is 1.8V.

6.2.2

Decoupling Capacitors

The use of decoupling capacitors on power supply pins, such as VDD, VSS, and AVDD is required.

Consider the following criteria when using decoupling capacitors:

•

Value and type of capacitor: A value of 0.1 μF (100 nF), 10-20V is recommended. The capacitor

should be a low Equivalent Series Resistance (low-ESR) capacitor and have resonance frequency

in the range of 20 MHz and higher. It is further recommended that ceramic capacitors be used.

•

Placement on the printed circuit board: The decoupling capacitors should be placed as close to

the pins as possible. It is recommended that the capacitors be placed on the same side of the

board as the device. If space is constricted, the capacitor can be placed on another layer on the

PCB using a via; however, ensure that the trace length from the pin to the capacitor is within 6 mm

in length.

•

Handling high-frequency noise: If the board is experiencing high-frequency noise, upward of tens

of MHz, add a second ceramic-type capacitor in parallel to the above described decoupling

capacitor. The value of the second capacitor can be in the range of 0.01 μF to 0.001 μF. Place this

second capacitor next to the primary decoupling capacitor. In high-speed circuit designs, consider

implementing a decade pair of capacitances as close to the power and ground pins as possible. For

example, 0.1 μF in parallel with 0.001 μF.

•

Maximizing performance: On the board layout from the power supply circuit, run the power and

return traces to the decoupling capacitors first, and then to the device pins. This ensures that the

decoupling capacitors are first in the power chain. Equally important is to keep the trace length

between the capacitor and the power pins to a minimum, thereby reducing PCB track inductance.

MGC3140 数据表(PDF) 24 Page - Microchip Technology