9

IXDN402 / IXDI402 / IXDF402

PIN CONFIGURATIONS

1

2

3

4

5

6

7

8

IN A

GND

INB

OUT A

V

S

OUT B

NC

NC

8 Lead PDIP (PI)

8 Pin SOIC (SI)

IXDN402

1

2

3

4

5

6

7

8

IN A

GND

INB

OUT A

V

S

OUT B

NC

NC

8 Lead PDIP (PI)

8 Pin SOIC (SI)

IXDI402

16 Pin SOIC

IXDN402SI-16

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

NC

IN A

NC

GND

GND

NC

IN B

NC

NC

OUT B

OUT B

VCC

VCC

OUT A

OUT A

NC

1

2

3

4

5

6

7

8

IN A

GND

INB

OUT A

V

S

OUT B

NC

NC

8 Lead PDIP (PI)

8 Pin SOIC (SI)

IXDF402

16 Pin SOIC

IXDI402SI-16

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

NC

IN A

NC

GND

GND

NC

IN B

NC

NC

OUT B

OUT B

VCC

VCC

OUT A

OUT A

NC

16 Pin SOIC

IXDF402SI-16

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

NC

IN A

NC

GND

GND

NC

IN B

NC

NC

OUT B

OUT B

VCC

VCC

OUT A

OUT A

NC

When designing a circuit to drive a high speed MOSFET

utilizing the IXDN402/IXDI402/IXDF402, it is very important to

observe certain design criteria in order to optimize performance

of the driver. Particular attention needs to be paid to Supply

Bypassing, Grounding, and minimizing the Output Lead

Inductance.

Say, for example, we are using the IXDN402 to charge a 1500pF

capacitive load from 0 to 25 volts in 25ns.

Using the formula: I=

∆V C / ∆t, where ∆V=25V C=1500pF &

∆t=25ns, we can determine that to charge 1500pF to 25 volts

in 25ns will take a constant current of 1.5A. (In reality, the

charging current won’t be constant, and will peak somewhere

around 2A).

SUPPLYBYPASSING

In order for our design to turn the load on properly, the IXDN402

must be able to draw this 1.5A of current from the power supply

in the 25ns. This means that there must be very low impedance

between the driver and the power supply. The most common

method of achieving this low impedance is to bypass the power

supply at the driver with a capacitance value that is an order of

magnitude larger than the load capacitance. Usually, this

would be achieved by placing two different types of bypassing

capacitors, with complementary impedance curves, very close

to the driver itself. (These capacitors should be carefully

selected and should have low inductance, low resistance and

high-pulse current-service ratings). Lead lengths may radiate

at high frequency due to inductance, so care should be taken

to keep the lengths of the leads between these bypass

capacitors and the IXDN402 to an absolute minimum.

GROUNDING

In order for the design to turn the load off properly, the IXDN402

must be able to drain this 1.5A of current into an adequate

grounding system. There are three paths for returning current

that need to be considered: Path #1 is between the IXDN402

and its load. Path #2 is between the IXDN402 and its power

supply. Path #3 is between the IXDN402 and whatever logic is

driving it. All three of these paths should be as low in resistance

and inductance as possible, and thus as short as practical. In

addition, every effort should be made to keep these three

ground paths distinctly separate. Otherwise, the returning

ground current from the load may develop a voltage that would

have a detrimental effect on the logic line driving the IXDN402.

OUTPUTLEADINDUCTANCE

Of equal importance to Supply Bypassing and Grounding are

issues related to the Output Lead Inductance. Every effort

should be made to keep the leads between the driver and its

load as short and wide as possible. If the driver must be placed

farther than 2” (5mm) from the load, then the output leads

should be treated as transmission lines. In this case, a twisted-

pair should be considered, and the return line of each twisted

pair should be placed as close as possible to

the ground pin

of the driver, and connected directly to the ground terminal

of the load.

Supply Bypassing, Grounding Practices And Output Lead inductance