AD7870SQ Analog Devices Inc, AD7870SQ Datasheet - Page 18

• Manufacturer Part Number: AD7870SQ
• Description: IC ADC 12BIT SAMPLING 3V 24-CDIP
• Manufacturer: Analog Devices Inc

Specifications of AD7870SQ

• Rohs Status: RoHS non-compliant
• Number Of Bits: 12
• Sampling Rate (per Second): 100k
• Data Interface: Serial, Parallel
• Number Of Converters: 1
• Power Dissipation (max): 95mW
• Voltage Supply Source: Dual ±
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Through Hole
• Package / Case: 24-CDIP (0.300", 7.62mm)

AD7870/AD7875/AD7876
AC Linearity Plot
When a sine wave of specified frequency is applied to the V
input of the AD7870/AD7875 and several million samples are
taken, a histogram showing the frequency of occurrence of each
of the 4096 ADC codes can be generated. From this histogram
data it is possible to generate an ac integral linearity plot as
shown in Figure 21. This shows very good integral linearity
performance from the AD7870/AD7875 at an input frequency
of 25 kHz. The absence of large spikes in the plot shows good
differential linearity. Simplified versions of the formulae used
are outlined below.
where:
INL(i) is the integral linearity at code i.
V(fs) and V(o) are the estimated full-scale and offset transitions.
V(i) is the estimated transition for the i
INL
–120
–30
–60
–90
0
( )
i
0
=
⎡
⎢
⎢
⎣
V
V
( )
( )
fs
i
−
−
V
V
Figure 20. IMD Plot
( )
( )
o
INPUT FREQUENCIES
SAMPLING FREQUENCY = 100kHz
IMD
o
F1 = 9.05kHz
F2 = 9.55kHz
T
ALL TERMS = 90.06dB
SECOND ORDER TERMS = 92.73dB
THIRD ORDER TERSM = 93.45dB
FREQUENCY (kHz)
A
= 25°C
×
4096
⎤
⎥
⎥
⎦
−
th
i
code.
5
0
IN
Rev. C | Page 18 of 28
V(i), the estimated code transition point, is derived as follows:
where:
A is the peak signal amplitude.
N is the number of histogram samples.
cum(i) =
V
–0.25
–0.50
0.25
( )
0.5
i
0
∑
=
0
−
i
n
A
=
0
511
×
V
Cos
( )
n
1023
[
π
Figure 21. AC INL Plot
occurrences.
×
cum
N
1535
( )
i
CODE
INPUT FREQUENCY = 25kHz
SAMPLE FREQUENCY = 100kHz
T
2047
]
A
= 25°C
2559
3071
3583
4095