Applications Information

GENERAL INFORMATION

Power supply bypass capacitors (01 mF) are recommended

for all applications

The LH0094 series is designed for positive input signals

only However negative input up to the supply voltage will

not damage the device

A clamp diode (

Figure 1 ) is recommended for those applica-

tions in which the inputs may be subjected to open circuit or

negative input signals

For basic applications (multiply divide square square root)

it is possible to use the device without any external adjust-

ments or components Two matched resistors are provided

internally to set m for square or square root

When using external resistors to set m such resistors

should be as close to the device as possible

SELECTION OF RESISTORS TO SET m

Internal Matched Resistors

TLH5695 – 2

No external resistors required strap as indicated

External Resistors

The exponent is set by 2 external resistors or it may be

TLH5695 – 3

R2

200X

R2

TLH5695 – 4

ACCURACY (ERROR)

The accuracy of the LH0094 is specified for both externally

adjusted and unadjusted cases

Although it is customary to specify the errors in percent of

full-scale (10V) it is seen from the typical performance

curves that the actual errors are in percent of reading Thus

the specified errors are overly conservative for small input

voltages An example of this is the LH0094 used in the mul-

tiplication mode The specified typical error is 025% of full-

scale (25 mV) As seen from the curve the unadjusted error

is

25 mV at 10V input but the error is less than 10 mV for

inputs up to 1V Note also that if either the multiplicand or

the multiplier is at less than 10V (5V for example) the unad-

justed error is less Thus the errors specified are at full-

scalethe worst case

The LH0094 is designed such that the user is able to exter-

nally adjust the gain and offset of the devicethus trim out

all of the errors of conversion In most applications the gain

adjustment is the only external trim needed for super accu-

racyexcept in division mode where a denominator offset

adjust is needed for small denominator voltages

EXPONENTS

The LH0094 is capable of performing roots to 01 and pow-

ers up to 10 However care should be taken when applying

these exponentotherwise results may be misinterpreted

For example consider the

th power of a number ie

0001 raised to 01 power is 05011 01 raised to the 01

power is 07943 and 10 raised to the 01 power is 12589

Thus it is seen that while the input has changed 4 decades

the output has only changed a little more than a factor of 2

It is also seen that with as little as 1 mV of offset the output

will also be greater than zero with zero input

3