ADC1207S080_2 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 02 — 7 August 2008 14 of 21
NXP Semiconductors
ADC1207S080
Single 12 bits ADC, up to 80 MHz with direct/ultra high IF sampling
Remark: In the following equations, P
noise
is the power of the terms which include the
effects of random noise, non-linearities, sampling time errors, and ‘quantization noise’.
11.2.1 SIgnal-to-Noise And Distortion (SINAD)
The ratio of the output signal power to the noise plus distortion power for a given sample
rate and input frequency, excluding the DC component:
11.2.2 Effective Number Of Bits (ENOB)
It is derived from SINAD and gives the theoretical resolution an ideal ADC would require
to obtain the same SINAD measured on the real ADC. A good approximation gives:
11.2.3 Total Harmonic Distortion (THD)
The ratio of the power of the harmonics to the power of the fundamental. For k − 1
harmonics the THD is:
where:
The value of k is usually 6 (i.e. calculation of THD is done on the first 5 harmonics).
11.2.4 Signal-to-Noise ratio (S/N)
The ratio of the output signal power to the noise power, excluding the harmonics and the
DC component is:
11.2.5 Spurious Free Dynamic Range (SFDR)
The number SFDR specifies available signal range as the spectral distance between the
amplitude of the fundamental and the amplitude of the largest spurious harmonic and
non-harmonic, excluding DC component:
SINAD dB[] 10log
10
P
signal
P
noise distortion+
----------------------------------------
=
ENOB
SINAD 1.76–
6.02
----------------------------------
=
THD dB[] 10log
10
P
harmonics
P
signal
-------------------------
=
P
harmonics
α
2
2
α
3
2
…α
k
2
+++=
P
signal
α
1
2
=
SN⁄ dB[] 10log
10
P
signal
P
noise
----------------
=
SFDR dB[] 20log
10
α
1
max S()
------------------
=
