AD7746 Analog Devices, AD7746 Datasheet - Page 3

• Manufacturer Part Number: AD7746
• Description: 24-bit, 2 Channel Capacitance to Digital Converter
• Manufacturer: Analog Devices

Specifications of AD7746

• Resolution (bits): 24bit
• # Chan: 2
• Sample Rate: n/a
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: Diff-Uni,SE-Uni
• Ain Range: (2Vref) p-p,± 4 pF (Delta C)
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

SPECIFICATIONS
V
Table 1.
Parameter
CAPACITIVE INPUT
CAPDAC
EXCITATION
TEMPERATURE SENSOR
VOLTAGE INPUT
DD
Conversion Input Range
Integral Nonlinearity (INL)
No Missing Codes
Resolution, p-p
Resolution Effective
Output Noise, rms
Absolute Error
Offset Error
System Offset Calibration Range
Offset Drift vs. Temperature
Gain Error
Gain Drift vs. Temperature
Allowed Capacitance to GND
Power Supply Rejection
Normal Mode Rejection
Channel-to-Channel Isolation
Full Range
Resolution
Drift vs. Temperature
Frequency
Voltage Across Capacitance
Average DC Voltage Across
Allowed Capacitance to GND
Resolution
Error
Differential VIN Voltage Range
Absolute VIN Voltage
Integral Nonlinearity (INL)
No Missing Codes
Resolution, p-p
Output Noise
Offset Error
Offset Drift vs. Temperature
Full-Scale Error
= 2.7 V to 3.6 V or 4.75 V to 5.25 V; GND = 0 V; EXC = 32 kHz; EXC = ±V
Capacitance
2
5
6
2, 4
7
3
2, 9
2
2
7
2
2
2
2
2
2
2
Min
24
–28
17
24
GND − 0.03
24
Typ
±4.096
16.5
19
2
–1
0.02
–26
0.3
65
55
70
21
164
26
32
±V
±V
±V
±V
0.1
±0.5
±2
±V
±3
16
3
±3
15
0.025
DD
DD
DD
DD
REF
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Max
±0.01
±4
32
±1
0.08
–24
60
1
28
<±40
100
±2
V
±15
0.1
DD
+ 0.03
DD
/2; –40°C to +125°C, unless otherwise noted.
Unit
pF
% of FSR
Bit
Bit
Bit
aF/√Hz
fF
aF
pF
aF/°C
% of FS
ppm of FS/°C
pF
fF/V
dB
dB
dB
pF
fF
ppm of FS/°C
kHz
V
V
V
V
mV
pF
°C
°C
°C
V
V
ppm of FS
Bit
Bits
µV rms
µV
nV/°C
% of FS
1
1
1
Conversion time ≥ 62 ms
Conversion time = 62 ms, see Table 5
50 Hz ± 1%, conversion time = 62 ms
60 Hz ± 1%, conversion time = 62 ms
Configurable via digital interface
External sensing diode
Conversion time = 122.1 ms
Test Conditions/Comments
Factory calibrated
Conversion time = 62 ms, see Table 5
See Table 5
25°C, V
After system offset calibration,
Excluding effect of noise
25°C, V
See Figure 9 and Figure 10
AD7746 only
7-bit CAPDAC
See Figure 11
V
Internal temperature sensor
V
Conversion time = 62 ms
See Table 6 and Table 7
Conversion time = 62 ms
See Table 6 and Table 7
REF
REF
internal
internal or V
DD
DD
= 5 V, after offset calibration
= 5 V
AD7745/AD7746
REF
= 2.5 V
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