AD7298 Analog Devices, AD7298 Datasheet - Page 12

• Manufacturer Part Number: AD7298
• Description: 8-Channel, 1MSPS, 12-Bit SAR ADC with Temperature Sensor
• Manufacturer: Analog Devices

Specifications of AD7298

• Resolution (bits): 12bit
• # Chan: 8
• Sample Rate: 1MSPS
• Interface: SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref),Uni 1.0V,Uni 1.25,Uni 2.0V,Uni 2.5V
• Adc Architecture: SAR
• Pkg Type: CSP

AD7298
TERMINOLOGY
Signal-to-Noise and Distortion Ratio (SINAD)
The measured ratio of signal-to-noise and distortion at the
output of the ADC. The signal is the rms amplitude of the
fundamental. Noise is the sum of all nonfundamental signals
up to half the sampling frequency (f
ratio is dependent on the number of quantization levels in the
digitization process; the more levels, the smaller the quantization
noise. The theoretical signal-to-noise and distortion ratio for
an ideal N-bit converter with a sine wave input is given by
Thus, the SINAD is 74 dB for an ideal 12-bit converter.
Total Harmonic Distortion (THD)
The ratio of the rms sum of harmonics to the fundamental. For
the AD7298, it is defined as
where V
V
sixth harmonics.
Peak Harmonic or Spurious Noise
The ratio of the rms value of the next largest component in the
ADC output spectrum (up to f
value of the fundamental. Typically, the value of this specification
is determined by the largest harmonic in the spectrum, but for
ADCs where the harmonics are buried in the noise floor, it is a
noise peak.
Integral Nonlinearity
The maximum deviation from a straight line passing through
the endpoints of the ADC transfer function. The endpoints are
zero scale, a point 1 LSB below the first code transition, and full
scale, a point 1 LSB above the last code transition.
4
, V
Signal-to-(Noise + Distortion) = (6.02 N + 1.76) dB
THD
5
, and V
1
is the rms amplitude of the fundamental, and V
(
dB
6
)
are the rms amplitudes of the second through
=
20
log
V
2
2
+
V
S
3
/2 and excluding dc) to the rms
2
+
V
V
S
1
/2), excluding dc. The
4
2
+
V
5
2
+
V
6
2
2
, V
Rev. B | Page 12 of 24
3
,
Differential Nonlinearity
The difference between the measured and the ideal 1 LSB
change between any two adjacent codes in the ADC.
Offset Error
The deviation of the first code transition (00…000) to
(00…001) from the ideal—that is, GND1 + 1 LSB.
Offset Error Match
The difference in offset error between any two channels.
Gain Error
The deviation of the last code transition (111…110) to
(111…111) from the ideal (that is, REF
offset error has been adjusted out.
Gain Error Matching
The difference in gain error between any two channels.
Track-and-Hold Acquisition Time
The track-and-hold amplifier returns to track mode at the end
of conversion. Track-and-hold acquisition time is the time
required for the output of the track-and-hold amplifier to reach
its final value, within ±1 LSB, after the end of conversion.
Power Supply Rejection Ratio (PSRR)
PSRR is defined as the ratio of the power in the ADC output at
full-scale frequency, f, to the power of a 100 mV p-p sine wave
applied to the ADC V
of the input varies from 5 kHz to 25 MHz.
where:
Pf is the power at frequency, f, in the ADC output.
Pf
S
is the power at frequency, f
PSRR (dB) = 10 log(Pf/Pf
DD
supply of frequency, f
S
S
)
, in the ADC output.
IN
− 1 LSB) after the
S
. The frequency