MCP1404 Microchip Technology Inc., MCP1404 Datasheet - Page 11

• Manufacturer Part Number: MCP1404
• Description: 4.5a Dual High-speed Power Mosfet Drivers
• Manufacturer: Microchip Technology Inc.

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
The total internal power dissipation in a MOSFET driver
is the summation of three separate power dissipation
elements.
4.5.1
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:
© 2007 Microchip Technology Inc.
Where:
Where:
P
P
P
P
T
L
Q
CC
f = Switching frequency
C
V
Power Dissipation
= Load power dissipation
= Total power dissipation
= Quiescent power dissipation
DD
T
= Operating power dissipation
CAPACITIVE LOAD DISSIPATION
= Total load capacitance
= MOSFET driver supply voltage
P
P
T
L
=
=
P
f C
L
×
+
P
T
Q
×
+
V
DD
P
CC
2
4.5.2
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
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:
Where:
Where:
P
Q
CC = Cross-conduction constant (A*sec)
f = Switching frequency
V
I
D = Duty cycle
I
V
QH
QL
=
DD
DD
= Quiescent current in the low state
= Quiescent current in the high state
(
= MOSFET driver supply voltage
= MOSFET driver supply voltage
QUIESCENT POWER DISSIPATION
OPERATING POWER DISSIPATION
I
QH
P
CC
×
D
MCP1403/4/5
=
+
CC f
I
QL
×
×
(
×
1 D
V
–
DS22022B-page 11
DD
)
) V
×
DD