AD7357

Preliminary Technical Data

Rev. PrD | Page 10 of 17

Peak Harmonic or Spurious Noise

Peak harmonic or spurious noise is defined as the ratio of the

rms value of the next largest component in the ADC output

fundamental. Normally, the value of this specification is

determined by the largest harmonic in the spectrum, but for

ADCs where the harmonics are buried in the noise floor, it is a

noise peak

Intermodulation Distortion

With inputs consisting of sine waves at two frequencies, fa and

fb, any active device with nonlinearities will create distortion

products at sum and difference frequencies of mfa ± nfb where

m, n = 0, 1, 2, 3, and so on. Intermodulation distortion terms

are those for which neither m nor n are equal to zero. For

example, the second-order terms include (fa + fb) and (fa − fb),

while the third-order terms include (2fa + fb), (2fa − fb), (fa +

2fb), and (fa − 2fb).

The AD7356 is tested using the CCIF standard where two input

frequencies near the top end of the input bandwidth are used.

In this case, the second-order terms are usually distanced in

frequency from the original sine waves, while the third-order

terms are usually at a frequency close to the input frequencies.

As a result, the second- and third-order terms are specified

separately. The calculation of the intermodulation distortion is

as per the THD specification, where it is the ratio of the rms

sum of the individual distortion products to the rms amplitude

of the sum of the fundamentals expressed in dBs.

Thermal Hysteresis

Thermal Hysteresis is defined as the absolute maximum change

of reference output voltage after the device is cycled through

temperature from either

It is expressed in ppm using the following equation:

6

10

)

25

(

)

_

(

)

25

(

)

(

×

°

−

°

=

C

V

HYS

T

V

C

V

ppm

V

REF

REF

REF

HYS

where:

T_HYS–.