AD7150 Analog Devices, AD7150 Datasheet - Page 18

• Manufacturer Part Number: AD7150
• Description: Ultra-Low Power, 2-Channel, Capacitance Converter for Proximity Sensing
• Manufacturer: Analog Devices

Specifications of AD7150

• Resolution (bits): 12bit
• # Chan: 2
• Sample Rate: n/a
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: SE-Uni
• Ain Range: 0.5 pF,1 pF,2 pF,4 pF
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

AD7150
SETUP REGISTERS
Ch1 Address Pointer 0x0B
Ch2 Address Pointer 0x0E
8 Bits, Read/Write, Factory Preset 0x0B
Table 10. Setup Registers Bit Map
Bit
Mnemonic
Default
Table 11. Setup Registers Bit Descriptions
Bit
7
6
5
4
3
2
1
0
Mnemonic
RngH
RngL
–
Hyst
ThrSettling
Description
Range bits set the CDC input range and determine the step for the AutoDAC function.
This bit should be 0 for the specified operation.
Hyst = 1 disables hysteresis in adaptive threshold mode. This bit has no effect in fixed threshold mode;
hysteresis is always disabled in the fixed threshold mode.
Determines the settling time constant of the data average and thus the settling time of the adaptive thresholds.
The response of the average to an input capacitance step change (that is, response to the change in the CDC
output data) is an exponential settling curve characterized by the following equation:
where:
Average(N) is the value of average N complete CDC conversion cycles after a step change on the input.
Average(0) is the value before the step change.
TimeConst can be selected in the range between 2 and 65,536 conversion cycle multiples, in steps of power of
2, by programming the ThrSettling bits.
See Figure 41.
RngH
Bit 7
RngH
0
TimeConst
Average
0
0
1
1
INPUT CAPACITANCE
(CDC DATA) CHANGE
(
N
RngL
)
=
Bit 6
Figure 41. Data Average Response to Data Step Change
=
0
2
(
Average
ThrSettlin
RngL
0
1
0
1
g
+
) 1
(
) 0
Bit 5
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–
0
+
Change
Capacitive Input Range (pF)
1 (
Bit 4
−
Hyst
DATA AVERAGE RESPONSE
0
e
N
0.5
/ TimeConst
2
1
4
)
Bit 3
TIME
ThrSettling (4-Bit Value)
Bit 2
AutoDAC Step (CAPDAC LSB)
0x0B
Bit 1
4
1
2
8
Bit 0