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ADVANCED COMMUNICATIONS & SENSING
USER GUIDE
SX8724SEVK
Evaluation Kit for SX8724S Data Acquisition System
ACS - Revision 1.0 May 2011
© Semtech Corp.
Noise Density (referred to the input)
– the input noise density V
ND,IN
is computed according to sample rate
previousely computed in the software with
OSR
,
N
ELCONV
and
fs
parameters:
ENOB DC
– Effective Number Of Bits (or Effective Bits)
1
– is computed according to the
samples rms
noise value. This value is a DC ENOB measure, not the dynamic ENOB that is measured using FFT and
SINAD. Its equation is as follows:
NFR
– the Noise Free Code Resolution (or flicker-free resolution) is the number of bits of resolution beyond
which it is impossible to distinctly resolve individual codes. Multiplying by a factor of 6.6 converts the
samples rms noise into a useful measure of peak-to-peak noise:
1.Digital averaging increases resolution and reduces noise. The effects of input-referred noise is reduced by digital averaging on the
buffer of samples used to compute the Measured System Performances. Therefore, the ENOB DC value can be higher than the sample
width limitation (>16 bits).
V
ND IN
,
V
N IN
,
samplerate
----------------------------------
=
Vrms
Hz
-------------
σ
ENOB
16
Log
2
σ
( )
–
=
bits
[
]
NFR
16
Log
2
σ
6.6
⋅
(
)
–
=
bits
[
]
