Rainbow Electronics MAX1421 - Manual (Page 16)

MAX1421
Total Harmonic Distortion (THD)
THD is typically the ratio of the RMS sum of the first four
harmonics of the input signal to the fundamental itself.
This is expressed as:
where V
1
is the fundamental amplitude, and V
2
through
V
5
are the amplitudes of the 2nd- through 5th-order har-
monics.
Spurious-Free Dynamic Range (SFDR)
SFDR is the ratio expressed in decibels of the RMS
amplitude of the fundamental (maximum signal compo-
nent) to the RMS value of the next largest spurious
component, excluding DC offset.
Intermodulation Distortion (IMD)
The two-tone IMD is the ratio expressed in decibels of
either input tone to the worst 3rd-order (or higher) inter-
modulation products. The individual input tone levels
are at -6.5dB full scale and their envelope is at -0.5dB
full scale.
THD
V V V V
V
1
= ×
+ + +
( ) 









20
10
2
2
3
2
4
2
5
2
log
12-Bit, 40Msps, +3.3V, Low-Power ADC
with Internal Reference
16 ______________________________________________________________________________________
CLK
INP
INTERFACE
PIPELINE ADC
OUTPUT
DRIVERS
REFIN REFP CML REFN OE
AV DD
AGND
DV DD
DGND
D11–D0
INN
PD
T/H
MAX1421
BANDGAP
REFERENCE
CLK
REF SYSTEM +
BIAS
Functional Diagram