Datasheet

MIC4416/7
DS20006077A-page 12  2018 Microchip Technology Inc.
5.0 APPLICATION INFORMATION
The MIC4416/7 is designed to provide high peak
current for charging and discharging capacitive loads.
The 1.2A peak value is a nominal value determined
under specific conditions. This nominal value is used to
compare its relative size to other low-side MOSFET
drivers. The MIC4416/7 is not designed to directly
switch 1.2A continuous loads.
5.1 Supply Bypass
Capacitors from VS to GND are recommended to
control switching and supply transients. Load current
and supply lead length are some of the factors that
affect capacitor size requirements.
A 4.7 μF or 10 μF tantalum capacitor is suitable for
many applications. Low-ESR (equivalent series
resistance) metalized film capacitors may also be
suitable. An additional 0.1 μF ceramic capacitor is
suggested in parallel with the larger capacitor to control
high-frequency transients.
The low ESR of tantalum capacitors makes them
especially effective, but also makes them susceptible
to uncontrolled inrush current from low impedance
voltage sources (such as NiCd batteries or automatic
test equipment). Avoid instantaneously applying
voltage capable of very high peak current directly to or
near tantalum capacitors without additional current
limiting. Normal power supply turn-on (slow rise time)
or printed circuit trace resistance is usually adequate
for normal product usage.
5.2 Circuit Layout
Avoid long power supply and ground traces. They
exhibit inductance that can cause voltage transients
(inductive kick). Even with resistive loads, inductive
transients can sometimes exceed the ratings of the
MOSFET and the driver.
When a load is switched off, supply lead inductance
forces current to continue flowing—resulting in a
positive voltage spike. Inductance in the ground
(return) lead to the supply has similar effects, except
the voltage spike is negative.
Switching transitions momentarily draw current from
VS to GND. This combines with supply lead inductance
to create voltage transients at turn on and turn off.
Transients can also result in slower apparent rise or fall
times when the driver’s ground shifts with respect to the
control input.
Minimize the length of supply and ground traces or use
ground and power planes when possible. Bypass
capacitors should be placed as close as practical to the
driver.
5.3 MOSFET Selection
5.3.1 STANDARD MOSFET
A standard N-channel power MOSFET is fully
enhanced with a gate-to-source voltage of
approximately 10V and has an absolute maximum
gate-to-source voltage of ±20V.
The MIC4416/7’s on-state output is approximately
equal to the supply voltage. The lowest usable voltage
depends upon the behavior of the MOSFET.
FIGURE 5-1: Using a Standard MOSFET.
5.3.2 LOGIC-LEVEL MOSFET
Logic-level N-channel power MOSFETs are fully
enhanced with a gate-to-source voltage of
approximately 5V and have an absolute maximum
gate-to-source voltage of ±10V. They are less common
and generally more expensive.
The MIC4416/7 can drive a logic-level MOSFET if the
supply voltage, including transients, does not exceed
the maximum MOSFET gate-to-source rating (10V).
FIGURE 5-2: Using a Logic-Level
MOSFET.
VS
CTL
G
GND
MIC4416
4.7μF
+8V to +18V
1
32
4
Load
Logic
Input
* Gate enhancement voltage
V
GS
*
+15V
Standard
MOSFET
IRFZ24
†
†
International Rectier
100m
:
, 60V MOSFET
0.1μF
Try a
15
:
, 15W
or
1kΩ, 1/4W
resistor
VS
CTL
G
GND
MIC4416
+4.5V to 10V*
1
32
4
Load
Logic
Input
* Gate enhancement voltage
(must not exceed 10V)
V
GS
*
+5V
Logic-Level
MOSFET
IRLZ44
†
†
International Rectier
28m
:
, 60V MOSFET
4.7μF
0.1μF
Try a
3
:
, 10W
or
100
:
, 1/4W
resistor