MCP1403-ESLASHP datasheet(11/22 Pages) MICROCHIP

11 / 22 page

DS22022B-page 11

MCP1403/4/5

Placing a ground plane beneath the MCP1403/4/5 will

help as a radiated noise shield as well as providing

some heat sinking for power dissipated within the

device.

4.5

Power Dissipation

The total internal power dissipation in a MOSFET driver

is the summation of three separate power dissipation

elements.

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:

4.5.2

QUIESCENT POWER DISSIPATION

The power dissipation associated with the quiescent

current draw depends upon the state of the input pin.

The MCP1403/4/5 devices have a quiescent current

draw when both inputs are high of 1.0 mA (typ) and

0.15 mA (typ) when both inputs are low. The quiescent

power dissipation is:

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 describes as:

PL PQ PCC

Where:

PT = Total power dissipation

PL = Load power dissipation

PQ = Quiescent power dissipation

PCC = Operating power dissipation

fCT

VDD

Where:

f = Switching frequency

CT = Total load capacitance

VDD = MOSFET driver supply voltage

IQH DIQL

1 D

–

()

() V

Where:

IQH = Quiescent current in the high state

D = Duty cycle

IQL = Quiescent current in the low state

VDD = MOSFET driver supply voltage

PCC

CC f

VDD

Where:

CC = Cross-conduction constant (A*sec)

f = Switching frequency

VDD = MOSFET driver supply voltage

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