8

All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.

Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality

Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without

notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and

reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result

from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.

For information regarding Intersil Corporation and its products, see www.intersil.com

FN7349.2

May 14, 2007

Applications Information

Product Description

The EL7158 is a high performance 40MHz pin driver. It

contains two analog switches connecting VH and VL to OUT.

Depending on the value of the IN pin, one of the two

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

enable (OE) is also supplied which opens both switches

simultaneously.

Due to the topology of the EL7158, both the VH and VL pins

can be connected to any voltage between the VS+ and VS-

pins, but VH must be greater than VL in order to prevent

turning on the body diode at the output stage.

Three-State Operation

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

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

can be any voltage between VH and VL, depending on the

previous state. At three-state, the output voltage can be

voltage can’t be pushed higher than VH or lower than VL

since the body diode at the output stage will turn on.

Supply Voltage Range and Input Compatibility

The EL7158 is designed for operation on supplies from 5V to

18V (4.5V to 18V maximum). Table 2 shows the

specifications for the relationship between the VS+, VS-, VH,

VL, and GND pins.

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

also compatible with TTL inputs.

Power Supply Bypassing

When using the EL7158, it is very important to use adequate

power supply bypassing. The high switching currents

developed by the EL7158 necessitate the use of a bypass

pins. It is 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 have some level of bypassing, especially if the EL7158

is driving highly capacitive loads.

Power Dissipation Calculation

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

EL7158 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

is greater than +125°C when calculated using Equation 2 ,

then one of the following actions must be taken:

Reduce

into the PCB (as compared to the standard JEDEC

JESD51-3)

De-rate the application either by reducing the switching

frequency, the capacitive load, or the maximum operating

PD

V

S

(

I

C

INT

(

V

S

2

f

)

C

L

(

V

OUT

2

f

)

×

×

+

×

×

+

×

=

(EQ. 1)

θ

JA

T

JMAX

T

MAX

–

PD

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

=

(EQ. 2)

EL7158