SC1302A/B/C/D/E/F

8

General Description

The SC1302A/B/C/D/E/F is a high speed, high peak current

dual MOSFET driver. It is designed to drive power MOSFETs

with ultra-low rise/fall time and propagation delays. As

the switching frequency of PWM controllers is increased

to reduce power converters volume and cost, fast rise and

fall times are necessary to minimize switching losses.

While a discrete solution can achieve reasonable drive

capability, implementing delay and other housekeeping

functions necessary for safe operation can become cum-

bersome and costly. The SC1302A/B/C/D/E/F presents a

total solution for the high-speed, high-power density

applications. Wide input supply range of 4.5V to16.5V

allows use in battery powered applications as well as dis-

tributed power systems.

Supply Bypass and Layout

A 4.7μF to 10μF tantalum bypass capacitor with low ESR

(equivalent series resistance) and an additional 0.1μF

ceramic capacitor in parallel are recommended as a supply

bypass to control switching and supply transients.

As with any high speed, high current circuit, proper layout

is critical in achieving optimum performance of the

SC1302A/B/C/D/E/F. Attention should be paid to the

proper placement of the driver, the switching MOSFET,

and the bypass capacitors.

The driver should be placed as close as possible to the

external MOSFETs to eliminate the possibility of oscillation

caused by trace inductance and the MOSFET gate capaci-

tance. A resistor in the range of 10ohm could be used in

series with the gate drive to damp the ringing if the drive

output path is not short enough. The bypass capacitors

should also be placed closely between V

CC

and GND of the

driver. A Schottky diode may be used to connect the

ground and the output pin to avoid latch-ups in some

applications.

Drive Capability and Power Dissipation

The SC1302A/B/C/D/E/F is able to deliver 1.6A peak

current for driving capacitive loads, such as MOSFETs.

Fast switching of the MOSFETs significantly reduces

switching losses for high frequency applications. Thermal

stress is reduced and system reliability is improved.

For simplicity, it is assumed that the gate capacitance of

a MOSFET is constant. The power delivered from the

power supply can be estimated based on this simplifica-

tion. The energy needed to charge the capacitor is given

by the following equation

2

ON

V

C

2

1

E

where C is the load capacitance and V is the output

voltage swing of the driver.

During turn off, the same amount of energy is dumped

to the ground. Therefore, the energy dissipated in one

switching cycle is:

E

2

The power dissipation due to the gate driving actions is

given by:

P

where, f is the switching frequency. With V

CC

= 12V, C =

1nF and f = 200kHz, the power dissipation per output is:

P

GATE

The corresponding supply current is:

mA

4

.

2

V

12

mW

29

V

P

I

CC

GATE

Thermal Information

The driver’s junction temperature must be kept within

the rated limit at any time. The application system has to

effectively remove the heat generated in the driver in

order for proper functions and performance. If the junc-

tion temperature reaches 150°C, the internal protection

circuit will be triggered to shut down the gate driver.

The power dissipation of the SC1302A/B/C/D/E/F should

be derated according to the following formula:

jA

T

C

125

pation

PowerDissi

A

where T

A

= ambient temperature.

Applications Information