Datasheet

AD7142
Rev. A | Page 25 of 72
Σ-Δ
16-BIT
CDC
16
STAGE_MAX_WORD0
STAGE_MAX_WORD1
STAGE_MAX_WORD2
STAGE_MAX_WORD3
STAGE_MIN_WORD0
STAGE_MIN_WORD1
STAGE_MIN_WORD2
STAGE_MIN_WORD3
STAGE_MAX_AVG
BANK 3 REGISTERS
STAGE_HIGH_THRESHOLD
BANK 3 REGISTERS
STAGE_MAX_TEMP
BANK 3 REGISTERS
MAX LEVEL
DETECTION
LOGIC
STAGE_MIN_AVG
BANK 3 REGISTER3
STAGE_LOW_THRESHOLD
BANK 3 REGISTERS
STAGE_MIN_TEMP
BANK 3 REGISTERS
BANK 3
REGISTERS
BANK 3
REGISTERS
05702-062
MIN LEVEL
DETECTION
LOGIC
Figure 37. Tracking the Minimum and Maximum Average Sensor Values
Table 13. Additional Information about Environmental Calibration and Adaptive Threshold Registers
Register
Register
Location
Description
NEG_THRESHOLD_SENSITIVITY Bank 2 Used in Equation 2. This value is programmed once at start up.
NEG_PEAK_DETECT Bank 2 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 min average CDC value. If the output of the CDC gets within the
NEG_PEAK_DETECT percentage of the min average, only then is the min average value
updated.
POS_THRESHOLD_SENSITIVITY Bank 2 Used in Equation 1. This value is programmed once at start up.
POS_PEAK_DETECT Bank 2 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 max average CDC value. If the output of the CDC gets within the
POS_PEAK_DETECT percentage of the min average, only then is the max average value
updated.
STAGE_OFFSET_LOW Bank 2
Used in Equation 2. An initial value (based on sensor characterization) is programmed
into this register at start up. The AD7142 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 STAGE_OFFSET_LOW_CLAMP value.
STAGE_OFFSET_HIGH Bank 2
Used in Equation 1. An initial value (based on sensor characterization) is programmed
into this register at start up. The AD7142 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 STAGE_OFFSET_HIGH_CLAMP value.
STAGE_OFFSET_HIGH_CLAMP Bank 2 Used by internal environmental calibration and adaptive threshold algorithms only.
An initial value (based on sensor characterization) is programmed into this register at
start up. The value in this register prevents a user from causing a sensor’s output value
to exceed the expected nominal value.
Set to the maximum expected sensor response, maximum change in CDC output code .
STAGE_OFFSET_LOW_CLAMP Bank 2 Used by internal environmental calibration and adaptive threshold algorithms only.
An initial value (based on sensor characterization) is programmed into this register at
start up. The value in this register prevents a user from causing a sensor’s output value
to exceed the expected nominal value.
Set to the minimum expected sensor response, minimum change in CDC output code .
STAGE_SF_AMBIENT Bank 3
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.
STAGE_HIGH_THRESHOLD Bank 3 Equation 1 value.
STAGE_LOW_THRESHOLD Bank 3 Equation 2 value.