AD7745 Analog Devices, AD7745 Datasheet - Page 9

• Manufacturer Part Number: AD7745
• Description: 24-bit, 1 Channel Capacitance to Digital Converter
• Manufacturer: Analog Devices

Specifications of AD7745

• Resolution (bits): 24bit
• # Chan: 1
• 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

0.0001
0.001
Figure 12. Capacitance Input Error vs. Leakage Current to GND,
Figure 13. Capacitance Input Error vs. Leakage Current to GND,
0.01
–10
–12
–10
–12
0.1
Figure 14. Capacitance Input Error vs. Resistance in Parallel
–2
–4
–6
–8
–2
–4
–6
–8
10
–250
–250
8
6
4
2
0
8
6
4
2
0
1
1
–200 –150 –100
–200 –150 –100
CIN(+) to EXC = 4 pF, CIN(−) to EXC = 0 pF,
CIN(+) to EXC =4 pF, CIN(−) to EXC = 0 pF,
2.7V
5V
3.3V
10
with Measured Capacitance
3V
PARALLEL RESISTANCE (MΩ)
CIN LEAKAGE TO GND (nA)
CIN LEAKAGE TO GND (nA)
VDD=3.3 V and 5 V
V
DD
= 2.7 V and 3 V
–50
–50
100
0
0
1000
50
50
100
100
10000
150
150
200
200
100000
250
250
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–0.05
–0.10
–0.15
–0.20
–0.2
–0.4
–0.6
–0.8
–1.0
0.20
0.15
0.10
0.05
–10
CIN(+) to EXC = 4 pF, the Same Configuration as in Figure 30
–2
–4
–6
–8
0.2
Figure 16. Capacitance Input Power Supply Rejection (PSR),
0
0
0
Figure 15. Capacitance Input Error vs. Serial Resistance,
2.5
0
CIN(+) to EXC = 21 pF, CIN(−) to EXC = 23 pF, V
0
Figure 17. CAPDAC Differential Nonlinearity (DNL)
16
the Same Configuration as in Figure 34.
1
3.0
32
2
SERIAL RESISTANCE (kΩ)
3.5
48
CAPDAC CODE
3
V
DD
4.0
64
(V)
4
80
AD7745/AD7746
4.5
5
96
DD
5.0
= 5 V,
6
112
128
5.5
7