AD7746 Analog Devices, AD7746 Datasheet - Page 8

• 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

AD7745/AD7746
TYPICAL PERFORMANCE CHARACTERISTICS
V
DD
–1000
–2000
–3000
–100
2000
1000
100
= 5 V, CIN(+) to EXC = 4 pF, the Same Configuration as in Figure 30
100
–25
–50
–75
80
60
40
20
75
50
25
0
Figure 7. Capacitance Input Offset Drift vs. Temperature,
0
0
–50
–50
Figure 8. Capacitance Input Gain Drift vs. Temperature,
–5
Figure 6. Capacitance Input Integral Nonlinearity,
V
DD
–4
= 5 V, the Same Configuration as in Figure 31
–25
–25
V
DD
= 5 V, CIN and EXC Pins Open Circuit
–3
0
0
–2
INPUT CAPACITANCE (pF)
TEMPERATURE (°C)
TEMPERATURE (°C)
25
25
–1
50
50
0
1
75
75
GAIN TC ≈ –26ppm/°C
2
100
100
3
125
125
4
150
150
5
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Figure 10. Capacitance Input Error vs. Capacitance between CIN and GND,
Figure 11. Capacitance Input Error vs. Capacitance between EXC and GND,
CIN(+) to EXC = 21 pF, CIN(−) to EXC = 23 pF, V
CIN(+) to EXC = 21 pF, CIN(−) to EXC = 23 pF, V
Figure 9. Capacitance Input Error vs. Capacitance between CIN and GND.
CIN(+) to EXC = 4 pF, CIN(−) to EXC = 0 pF, V
18
16
14
12
10
–2
18
16
14
12
10
–2
–1
8
6
4
2
0
8
6
4
2
0
5
4
3
2
1
0
0
0
0
50
50
50
the Same Configuration as in Figure 34
the Same Configuration as in Figure 34
the Same Configuration as in Figure 33
100
100
100
CAPACITANCE EXC PIN TO GND (pF)
CAPACITANCE CIN PIN TO GND (pF)
CAPACITANCE CIN PIN TO GND (pF)
150
150
150
2.7V
200
200
200
2.7V
3V
250
250
250
3V
300
300
300
DD
3.3V
DD
DD
= 2.7 V, 3 V, 3.3 V, and 5 V,
= 2.7 V, 3 V, 3.3 V, and 5 V,
= 2.7 V, 3 V, 3.3 V, and 5 V,
3.3V
350
350
350
5V
2.7V
400
400
400
5V
3.3V
450
450
450
3V
5V
500
500
500