10

IXDN404 / IXDI404 / IXDF404

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)

IXDN404

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)

IXDI404

16 Pin SOIC

IXDN404SI-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)

IXDF404

16 Pin SOIC

IXDI404SI-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

IXDF404SI-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 IXDN404/IXDI404/IXDF404, 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, the IXDN404 is being used to charge a

2500pF capacitive load from 0 to 25 volts in 25ns.

Using the formula: I=

∆V C / ∆t, where ∆V=25V C=2500pF &

∆t=25ns, one can determine that to charge 2500pF to 25 volts

in 25ns will take a constant current of 2.5A. (In reality, the

charging current won’t be constant and will peak somewhere

around 4A).

SUPPLYBYPASSING

In order for the design to turn the load on properly, the IXDN404

must be able to draw this 2.5A 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 a 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, low

inductance, low resistance, high-pulse current-service

capacitors). 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 IXDN404

to an absolute minimum.

GROUNDING

In order for the design to turn the load off properly, the IXDN404

must be able to drain this 2.5A of current into an adequate

grounding system. There are three paths for returning current

that need to be considered: Path #1 is between the IXDN404

and its load. Path #2 is between the IXDN404 and its power

supply. Path #3 is between the IXDN404 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 IXDN404.

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