tda8768a NXP Semiconductors, tda8768a Datasheet - Page 24

• Manufacturer Part Number: tda8768a
• Description: 12-bit, 70 Msps Analog-to-digital Converter Adc
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 09656
Product data
Fig 26. Spectrum of full-scale input sine wave with frequency f
12.1.2 Dynamic parameters (single tone)
Figure 26
conforming to coherent sampling (f
is number of samples, M and N being relatively prime), and digitized by the ADC
under test.
Remark: in the following equations, P
effects of random noise, non-linearities, sampling time errors, and “quantization
noise”.
Signal-to-noise and distortion (SINAD):
noise plus distortion power for a given sample rate and input frequency, excluding the
DC component:
Effective Number of Bits (ENOB):
theoretical resolution an ideal ADC would require to obtain the same SINAD
measured on the real ADC. A good approximation gives:
Total Harmonic Distortion (THD):
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).
SINAD db
ENOB
THD dB
P
P
magnitude
harmonics
signal
=
=
shows the spectrum of a full-scale input sine wave with frequency f
a
=
SINAD dB
=
2
1
=
10
a
a 1
10
log
2
2
+
log
Rev. 02 — 03 July 2002
a
P
-------------------------- -
harmonics
2
3
----------------------------------------- -
P
P
+
noise
–
signal
s
a
1 76
P
2
k
a 2
signal
+
distortion
SFDR
12-bit, 70 Msps Analog-to-Digital Converter (ADC)
t
t/
.
6 02
f
The ratio of the power of the harmonics to the
It is derived from SINAD and gives the
s
noise
= M/N, where M is the number of cycles and N
a 3
measured output range
is the power of the terms which include the
The ratio of the output signal power to the
a k
© Koninklijke Philips Electronics N.V. 2002. All rights reserved.
FCE710
fs/2
TDA8768A
t
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