8

FN7279.2

March 9, 2006

Applications Information

Product Description

The EL7155 is a high performance 40MHz pin driver. It

two switches will be closed and the other switch open. An

output enable (OE) is also supplied which opens both

switches simultaneously.

The EL7155 is available in both the 8 Ld SO and the 8 Ld

PDIP packages. The relevant package should be chosen

depending on the calculated power dissipation.

3-state Operation

When the OE pin is low, the output is 3-state (floating.) The

output voltage is the parasitic capacitance’s voltage. It can

previous state. At 3-state, the output voltage can be pushed

diode at the output stage will turn on.

Supply Voltage Range and Input Compatibility

The EL7155 is designed for operation on supplies from 5V to

15V (4.5V to 16.5V maximum). The table on page 6 shows

All input pins are compatible with both 3V and 5V CMOS

also compatible with TTL inputs.

Power Supply Bypassing

When using the EL7155, it is very important to use adequate

power supply bypassing. The high switching currents

developed by the EL7155 necessitate the use of a bypass

recommended that a 2.2µF tantalum capacitor be used in

parallel with a 0.1µF low-inductance ceramic MLC capacitor.

These should be placed as close to the supply pins as

have some level of bypassing, especially if the EL7155 is

driving highly capacitive loads.

Power Dissipation Calculation

When switching at high speeds, or driving heavy loads, the

EL7155 drive capability is limited by the rise in die

temperature brought about by internal power dissipation. For

reliable operation die temperature must be kept below

dissipation for a given application prior to selecting the

package type.

Power dissipation may be calculated:

where:

GND)

f is frequency

Having obtained the application’s power dissipation, a

maximum package thermal coefficient may be determined,

where:

PD is the power dissipation calculated above

θ

PDIP8 package when using a standard JEDEC JESD51-3

calculated using the equation above, then one of the

following actions must be taken:

Reduce

θ

into the PCB (as compared to the standard JEDEC

JESD51-3)

Use the PDIP8 instead of the SO8 package

De-rate the application either by reducing the switching

frequency, the capacitive load, or the maximum operating

PD

(

(

2

f

)

(

2

f

)

×

×

+

×

×

+

×

=

θ

JA

(

–

PD

----------------------------------------------

=

EL7155