Datasheet

 2018 Microchip Technology Inc. DS20006077A-page 13
MIC4416/7
At low voltages, the MIC4416/7’s internal P- and
N-channel MOSFET’s on-resistance will increase and
slow the output rise time. Refer to the Typical
Performance Curves graphs.
5.4 Inductive Loads
Switching off an inductive load in a low-side application
forces the MOSFET drain higher than the supply
voltage (as the inductor resists changes to current). To
prevent exceeding the MOSFET’s drain-to-gate and
drain-to-source ratings, a Schottky diode should be
connected across the inductive load.
FIGURE 5-3: Switching an Inductive
Load.
5.5 Power Dissipation
The maximum power dissipation must not be exceeded
to prevent die meltdown or deterioration.
Power dissipation in on/off switch applications is
negligible.
Fast repetitive switching applications, such as SMPS
(switch mode power supplies), cause a significant
increase in power dissipation with frequency. Power is
dissipated each time current passes through the
internal output MOSFETs when charging or
discharging the external MOSFET. Power is also
dissipated during each transition when some current
momentarily passes from VS to GND through both
internal MOSFETs.
Power dissipation is the product of supply voltage and
supply current:
EQUATION 5-1:
Supply current is a function of supply voltage, switching
frequency, and load capacitance. Determine this value
from Figure 2-23 and Figure 2-24 or measure it in the
actual application.
Do not allow P
D
to exceed P
D(MAX)
.
T
J
(junction temperature) is the sum of T
A
(ambient
temperature) and the temperature rise across the
thermal resistance of the package. In another form:
EQUATION 5-2:
Maximum power dissipation at 20°C with the driver
soldered to a 0.25 in
2
ground plane is approximately
600 mW.
FIGURE 5-4: Heat Sink Plane.
The SOT-143 package θ
JA
(junction-to-ambient
thermal resistance) can be improved by using a heat
sink larger than the specified 0.25 in
2
ground plane.
Significant heat transfer occurs through the large
(GND) lead. This lead is an extension of the paddle to
which the die is attached.
5.6 High Frequency Operation
Although the MIC4416/7 driver will operate at
frequencies greater than 1 MHz, the MOSFET’s
capacitance and the load will affect the output
waveform (at the MOSFET’s drain).
For example, an MIC4416/IRL3103 test circuit using a
47Ω 5W load resistor will produce an output waveform
that closely matches the input signal shape up to about
500 kHz. The same test circuit with a 1 kΩ load resistor
operates only up to about 25 kHz before the MOSFET
source waveform shows significant change.
On
O
VS
CTL
G
GND
MIC4416
V
SUPPLY
1
32
4
Schottky
Diode
V
SWITCHED
4.7μF
0.1μF
P
D
V
S
I
S
=
Where:
P
D
= Power dissipation (in watts)
V
S
= Supply voltage (in volts)
I
S
= Supply current (in amps)
P
DMAX
150 T
A
–
220
---------------------

Where:
P
D(MAX)
= Maximum power dissipation (in watts)
150 = Maximum junction temperature (in °C)
T
A
= Ambient temperature (in °C)
220 = Package thermal resistance (in °C/W)
CTL
G
VS
GND
PCB heat sink/
ground plane
PCB traces