MCP1403-ESLASHP datasheet(10/22 Pages) MICROCHIP

10 / 22 page

MCP1403/4/5

DS22022B-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

MOSFET driver like the MCP1403/4/5 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 driv-

ers rise time (tR), fall time (tF), and propagation delays

(tD1 and tD2). The MCP1403/4/5 family of drivers can

typically charge and discharge a 2200 pF load capaci-

tance in 15 ns along with a typical matched propaga-

tion delay of 40 ns. Figure 4-1 and Figure 4-2 show the

test circuit and timing waveform used to verify the

MCP1403/4/5 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, 2.5A are needed

to charge a 2200 pF load with 18V in 16 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

VDD and GND pins 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.

0.1 µF

+5V

10%

90%

10%

90%

10%

90%

18V

1µF

MCP1403

CL = 2200 pF

Input

Output

tD1

tD2

Output

DD = 18V

Ceramic

Input

(1/2 MCP1405)

90%

Input

tD1

tD2

Output

10%

+5V

18V

90%

0.1 µF

1µF

MCP1404

CL = 2200 pF

Input

Output

DD = 18V

Ceramic

Input

(1/2 MCP1405)

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