MCP1406-ESLASHAT datasheet(10/22 Pages) MICROCHIP

10 / 22 page

MCP1406/07

DS22019A-page 10

4.0

APPLICATION INFORMATION

4.1

General Information

MOSFET drivers are high-speed, high current devices

which are intended to provide high peak currents to

charge 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 MCP1406/07 family can be used to provide

additional drive 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 MCP1406/07 family of

devices is able to make this transition very quickly.

Figure 4-1 and Figure 4-2 show the test circuits and

timing waveforms used to verify the MCP1406/07 tim-

ing.

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, 2.25A are

needed to charge a 2500 pF load with 18V in 20 ns.

To operate the MOSFET driver over a wide frequency

range with low supply impedance, a ceramic and low

ESR film capacitor are 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 1, 8 and 4, 5 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 a ground

plane or ground trace located under the MOSFET gate

drive signals, separate analog and power grounds, and

local driver decoupling.

0.1 µF

+5V

10%

90%

10%

90%

10%

90%

18V

1µF

MCP1406

CL = 2500 pF

Input

Output

tD1

tD2

Output

DD = 18V

Ceramic

90%

Input

tD1

tD2

Output

10%

+5V

18V

90%

0.1 µF

1µF

MCP1407

CL = 2500 pF

Input

Output

DD = 18V

Ceramic

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