MCP1402 datasheet(11/20 Pages) MICROCHIP

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DS22052A-page 11

MCP1401/02

4.5

Power Dissipation

The total internal power dissipation in a MOSFET driver

is the summation of three separate power dissipation

elements.

EQUATION 4-1:

4.5.1

CAPACITIVE LOAD DISSIPATION

The power dissipation caused by a capacitive load is a

direct function of frequency, total capacitive load, and

supply voltage. The power lost in the MOSFET driver

for a complete charging and discharging cycle of a

MOSFET is shown in Equation 4-2.

EQUATION 4-2:

4.5.2

QUIESCENT POWER DISSIPATION

The power dissipation associated with the quiescent

current draw depends upon the state of the input pin.

The MCP1401/02 devices have a quiescent current

draw when the input is high of 850 mA (typ) and

100 mA (typ) when the input is low. The quiescent

power dissipation is shown in Equation 4-3.

EQUATION 4-3:

4.5.3

OPERATING POWER DISSIPATION

The operating power dissipation occurs each time the

MOSFET driver output transitions because for a very

short period of time both MOSFETs in the output stage

are on simultaneously. This cross-conduction current

leads to a power dissipation described in Equation 4-4.

EQUATION 4-4:

Where:

Total power dissipation

Load power dissipation

Quiescent power dissipation

PCC

Operating power dissipation

Where:

Switching frequency

Total load capacitance

VDD

MOSFET driver supply voltage

–

()

() V

Where:

IQH

Quiescent current in the high

state

Duty cycle

IQL

Quiescent current in the low

state

VDD

MOSFET driver supply voltage

Where:

Cross-conduction constant

(A*sec)

Switching frequency

VDD

MOSFET driver supply voltage

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