AD7148 Analog Devices, AD7148 Datasheet - Page 25

• Manufacturer Part Number: AD7148
• Manufacturer: Analog Devices

Specifications of AD7148

• Resolution (bits): 16bit
• # Chan: 8
• Sample Rate: 250kSPS
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: SE-Uni
• Ain Range: ± 8 pF (Delta C)
• Adc Architecture: Sigma-Delta
• Pkg Type: CSP

Table 14. Additional Information About Environmental Calibration and Adaptive Threshold Registers
Bit
NEG_THRESHOLD_SENSITIVITY
NEG_PEAK_DETECT
POS_THRESHOLD_SENSITIVITY
POS_PEAK_DETECT
STAGEx_OFFSET_LOW
STAGEx_OFFSET_HIGH
STAGEx_OFFSET_HIGH_CLAMP
STAGEx_OFFSET_LOW_CLAMP
STAGEx_SF_AMBIENT
STAGEx_HIGH_THRESHOLD
STAGEx_LOW_THRESHOLD
16-BIT
CDC
Σ-Δ
Register
Location
Bank 2
Bank 2
Bank 2
Bank 2
Bank 2
Bank 2
Bank 2
Bank 2
Bank 3
Bank 3
Bank 3
Figure 35. Tracking the Minimum and Maximum Average Sensor Values
16
Description
Used in Equation 2. This value is programmed once at startup.
Used by internal adaptive threshold logic only.
The NEG_PEAK_DETECT is set to a percentage of the difference between the ambient
CDC value and the minimum average CDC value. If the output of the CDC gets within
the NEG_PEAK_DETECT percentage of the minimum average, only then is the minimum
average value updated.
Used in Equation 1. This value is programmed once at startup.
Used by internal adaptive threshold logic only.
The POS_PEAK_DETECT is set to a percentage of the difference between the ambient
CDC value and the maximum average CDC value. If the output of the CDC gets within
the POS_PEAK_DETECT percentage of the maximum average, only then is the maximum
average value updated.
Used in Equation 2. An initial value (based on sensor characterization) is programmed
into this register at startup. The AD7148 on-chip calibration algorithm automatically
updates this register based on the amount of sensor drift due to changing ambient
conditions. Set to 80% of the STAGEx_OFFSET_LOW_CLAMP value.
Used in Equation 1. An initial value (based on sensor characterization) is programmed
into this register at startup. The AD7148 on-chip calibration algorithm automatically
updates this register based on the amount of sensor drift due to changing ambient
conditions. Set to 80% of the STAGEx_OFFSET_HIGH_CLAMP value.
Used by internal environmental calibration and adaptive threshold algorithms only.
An initial value (based on sensor characterization) is programmed into this register at
startup. The value in this register prevents a user from causing sensor output value to
exceed the expected nominal value.
Set to the maximum expected sensor response, maximum change in CDC output code.
Used by internal environmental calibration and adaptive threshold algorithms only.
An initial value (based on sensor characterization) is programmed into this register at
startup. The value in this register prevents a user from causing sensor output value to
exceed the expected nominal value.
Set to the minimum expected sensor response, minimum change in CDC output code .
Used in Equation 1 and Equation 2. This is the ambient sensor output, when the sensor
is not touched, as calculated using the slow FIFO.
Equation 1 value.
Equation 2 value.
MAX LEVEL
DETECTION
DETECTION
MIN LEVEL
LOGIC
LOGIC
Rev. A | Page 25 of 56
STAGEx_HIGH_THRESHOLD
STAGEx_LOW_THRESHOLD
STAGEx_MAX_WORD0
STAGEx_MAX_WORD1
STAGEx_MAX_WORD2
STAGEx_MAX_WORD3
STAGEx_MIN_WORD0
STAGEx_MIN_WORD1
STAGEx_MIN_WORD2
STAGEx_MIN_WORD3
STAGEx_MAX_TEMP
BANK 3 REGISTERS
BANK 3 REGISTERS
BANK 3 REGISTERS
STAGEx_MIN_TEMP
BANK 3 REGISTERS
BANK 3 REGISTERS
STAGEx_MAX_AVG
BANK 3 REGISTER3
STAGEx_MIN_AVG
BANK 3 REGISTERS
BANK 3 REGISTERS
AD7148