MCP1401/02
DS20002052D-page 10 2007-2014 Microchip Technology Inc.
4.0 APPLICATION INFORMATION
4.1 General Information
MOSFET drivers are high-speed, high-current devices
which are intended to source/sink high peak currents to
charge/discharge the gate capacitance of external
MOSFETs or IGBTs. In high-frequency switching power
supplies, the PWM controller may not have the drive
capability to directly drive the power MOSFET. A
MOSFET driver like the MCP1401/02 family can be
used to provide additional source/sink current
capability.
4.2 MOSFET Driver Timing
The ability of a MOSFET driver to transition from a fully-
off state to a fully-on state is characterized by the
driver’s rise time (t
R
), fall time (t
F
), and propagation
delays (t
D1
and t
D2
). The MCP1401/02 family of drivers
can typically charge and discharge a 470 pF load
capacitance in 19 ns, along with a typical matched
propagation delay of 35 ns. Figures 4-1 and 4-2 show
the test circuit and timing waveform used to verify the
MCP1401/02 timing.
FIGURE 4-1: Inverting Driver Timing
Waveform.
FIGURE 4-2: Non-Inverting Driver Timing
Waveform.
4.3 Decoupling Capacitors
Careful layout and decoupling capacitors are highly
recommended when using MOSFET drivers. Large
currents are required to charge and discharge
capacitive loads quickly. For example, approximately
550 mA are needed to charge a 470 pF load with 18V
in 15 ns.
To operate the MOSFET driver over a wide frequency
range with low supply impedance, it is recommended to
place a ceramic and low ESR film capacitor in parallel
between the driver V
DD
and GND. A 1.0 µF low ESR
film capacitor and a 0.1 µF ceramic capacitor placed
between pins 2 and 1 should be used. These
capacitors should be placed close to the driver to
minimize circuit board parasitics and provide a local
source for the required current.
4.4 PCB Layout Considerations
Proper Printed Circuit Board (PCB) layout is important
in a high-current, fast switching circuit to provide proper
device operation and robustness of design. PCB trace
loop area and inductance should be minimized by the
use of ground planes or trace under MOSFET gate
drive signals, separate analog and power grounds, and
local driver decoupling.
Placing a ground plane beneath the MCP1401/02 will
help as a radiated noise shield and it will provide some
heat sinking for power dissipated within the device.
0.1 µF
+5V
10%
90%
10%
90%
10%
90%
18V
1µF
0V
0V
MCP1401
C
L
= 470 pF
Input
Input
Output
t
D1
t
F
t
D2
Output
t
R
V
DD
=18V
Ceramic
90%
Input
t
D1
t
F
t
D2
Output
t
R
10%
10%
10%
+5V
18V
0V
0V
90%
90%
0.1 µF
1µF
MCP1402
C
L
= 470 pF
Input Output
V
DD
=18V
Ceramic
