MCP1401/02
4.5.2
QUIESCENT POWER DISSIPATION
4.5
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.
The total internal power dissipation in a MOSFET driver
is the summation of three separate power dissipation
elements.
EQUATION 4-1:
PT = PL + PQ + PCC
Where:
EQUATION 4-3:
PQ = (IQH × D + IQL × (1 – D)) × VDD
PT
PL
=
=
=
=
Total power dissipation
Load power dissipation
Where:
PQ
Quiescent power dissipation
Operating power dissipation
IQH
=
Quiescent current in the high
state
PCC
D
=
=
Duty cycle
4.5.1
CAPACITIVE LOAD DISSIPATION
IQL
Quiescent current in the low
state
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.
VDD
=
MOSFET driver supply voltage
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 4-2:
2
PL = f × CT × VDD
Where:
EQUATION 4-4:
PCC = CC × f × VDD
Where:
f
CT
=
=
=
Switching frequency
Total load capacitance
MOSFET driver supply voltage
VDD
CC
=
Cross-conduction constant
(A*sec)
f
=
=
Switching frequency
VDD
MOSFET driver supply voltage
© 2007 Microchip Technology Inc.
DS22052A-page 11
MICROCHIP [ MICROCHIP ]
