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ENOB +
SINAD * 1.76
6.02
(3)
THD + 10Log
10
P
S
P
D
(4)
SNR + 10Log
10
P
S
P
N
(1)
SINAD + 10Log
10
P
S
P
N
) P
D
(2)
ADS5500
SBAS303F – DECEMBER 2003 – REVISED FEBRUARY 2007
Offset Error Effective Number of Bits (ENOB)
The offset error is the difference, given in number of The ENOB is a measure of a converter's
LSBs, between the ADC's actual average idle performance as compared to the theoretical limit
channel output code and the ideal average idle based on quantization noise.
channel output code. This quantity is often mapped
into mV.
Temperature Drift
Total Harmonic Distortion (THD)
The temperature drift coefficient (with respect to gain
THD is the ratio of the power of the fundamental (P
S
)
error and offset error) specifies the change per
to the power of the first eight harmonics (P
D
).
degree Celsius of the parameter from T
MIN
to T
MAX
. It
is calculated by dividing the maximum deviation of
the parameter across the T
MIN
to T
MAX
range by the
difference T
MAX
-T
MIN
.
THD is typically given in units of dBc (dB to carrier).
Signal-to-Noise Ratio
Spurious-Free Dynamic Range (SFDR)
SNR is the ratio of the power of the fundamental (P
S
)
The ratio of the power of the fundamental to the
to the noise floor power (P
N
), excluding the power at
highest other spectral component (either spur or
DC and the first eight harmonics.
harmonic). SFDR is typically given in units of dBc
(dB to carrier).
Two-Tone Intermodulation Distortion
IMD3 is the ratio of the power of the fundamental (at
SNR is either given in units of dBc (dB to carrier)
frequencies f1 and f2) to the power of the worst
when the absolute power of the fundamental is used
spectral component at either frequency 2f
1
–f
2
or
as the reference, or dBFS (dB to full scale) when the
2f
2
–f
1
. IMD3 is either given in units of dBc (dB to
power of the fundamental is extrapolated to the
carrier) when the absolute power of the fundamental
converter's full-scale range.
is used as the reference, or dBFS (dB to full scale)
Signal-to-Noise and Distortion (SINAD)
when the power of the fundamental is extrapolated to
SINAD is the ratio of the power of the fundamental
the converter's full-scale range.
(P
S
) to the power of all the other spectral
DC Power Supply Rejection Ratio (DC PSRR)
components including noise (P
N
) and distortion (P
D
),
The DC PSSR is the ratio of the change in offset
but excluding dc.
error to a change in analog supply voltage. The DC
PSRR is typically given in units of mV/V.
Reference Error
SINAD is either given in units of dBc (dB to carrier)
The reference error is the variation of the actual
when the absolute power of the fundamental is used
reference voltage (V
REFP
– V
REFM
) from its ideal value.
as the reference, or dBFS (dB to full scale) when the
The reference error is typically given as a
power of the fundamental is extrapolated to the
percentage.
converter's full-scale range.
Voltage Overload Recovery Time
The voltage overload recovery time is defined as the
time required for the ADC to recover to within 1% of
the full-scale range in response to an input voltage
overload of 10% beyond the full-scale range.
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