mic44f18 Micrel Semiconductor, mic44f18 Datasheet - Page 11

• Manufacturer Part Number: mic44f18
• Description: Mic44f18,mic44f19,mic44f20 6a High Speed Mosfet Drivers In 2mm ? 2mm Package
• Manufacturer: Micrel Semiconductor

January 2007
Micrel, Inc.
Supply Current Power Dissipation
Power is dissipated in the MIC44F18 even if is there is
nothing being driven. The supply current is drawn by the
bias for the internal circuitry, the level shifting circuitry and
shoot-through current in the output drivers. The supply
current is proportional to operating frequency and the V
voltage. The typical characteristic graphs show how supply
current varies with switching frequency and supply voltage.
The power dissipated by the MIC44F18 due to supply
current is
Total Power Dissipation and Thermal Considerations
Total power dissipation in the Driver equals the power
dissipation caused by driving the external MOSFETs plus
the supply current.
The die temperature may be calculated once the total
power dissipation is known.
The following graphs help determine the maximum
gate
switching frequency, supply voltage and ambient
temperature.
Figure 6A shows the power dissipation in the driver for
different values of gate charge with V
shows the power dissipation at V
show the maximum power dissipation for a given
ambient temperature for the MLF and ePad packages.
The maximum operating frequency of the driver may
be limited by the maximum power dissipation of the
driver package.
Where
T
T
Pdiss
θJC is the thermal resistance from junction-to-
ambient air (°C/W)
T
Pdiss
Pdiss
Pdiss
A
J
J
is the junction temperature (°C)
is the Maximum ambient temperature
charge that can be driven with respect to
=
T
TOTAL
TOTAL
drive
SUPPLY
A
+
Pdiss
is the power dissipation of the Driver
=
=
P
DRIVER
=
Pdiss
V
TOTAL
DD
SUPPLY
×
R
I
×
DD
ON
θ
JA
+
+
R
Pdiss
R
DD
G
ON
=12V. Figure 6C
+
DD
R
=5V. Figure 6B
DRIVE
G
_
FET
DD
11
Figure 6C. Max. Driver Power Dissipation
Figure 6A. Driver Power Dissipation
Figure 6B. Driver Power Dissipation
MIC44F18/19/20
M9999-011207