MCP1402 datasheet(10/20 Pages) MICROCHIP

10 / 20 page

MCP1401/02

DS22052A-page 10

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 MOS-

FET 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 are characterized by the

drivers rise time (tR), fall time (tF), and propagation

delays (tD1 and tD2). 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. Figure 4-1 and Figure 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, a ceramic and low

ESR film capacitor is recommended to be placed in

parallel between the driver VDD 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

minimized circuit board parasitics and provide a local

source for the required current.

4.4

PCB Layout Considerations

Proper 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 as well as providing

some heat sinking for power dissipated within the

device.

0.1 µF

+5V

10%

90%

10%

90%

10%

90%

18V

1µF

MCP1401

CL = 470 pF

Input

Output

tD1

tD2

Output

VDD = 18V

Ceramic

90%

Input

tD1

tD2

Output

10%

+5V

18V

90%

0.1 µF

1µF

MCP1402

CL = 470 pF

Input

Output

VDD = 18V

Ceramic

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