User Manual
791
Rev. 1.1
2019-03-18
TLE984xQX
Microcontroller with LIN and Power Switches for Automotive Applications
10-Bit Analog Digital Converter (ADC1)
24.6
Calibration Unit
24.6.1
Functional Description
The calibration unit of the Measurement Core module is dedicated to cancel offset and gain errors out of the
signal chain. The upcoming two chapter describe usage and setup of the calibration unit.
24.6.1.1 Method for determining the Calibration Parameters
As mentioned in the introduction of the calibration unit, the module can be used to correct gain and offset
errors caused by non-idealities in the measurement chain. This non-idealities are caused by the
corresponding measurement chain modules.
Those first order non-idealities are:
• Offset and Gain Error of ADC1.
• Offset and Gain Error of the Attenuator (especially voltage measurement).
• Offset and Gain Error of Reference Voltage.
All these factors are summed up in the overall Gain (factor
b
) and overall Offset (adder
a
) of the complete
measurement chain. They are calculated from a two point test result and stored inside the NVM.
Note:
The calibration of the VBAT_SENSE-Pin and the HV-Monitoring-Pins was done without
external resistor.
24.6.1.2 Setup of Calibration Unit
Each channel has its own calibration unit and thus also its dedicated Gain and Offset parameter. These
parameters are stored in a 100TP page of the Flash Module. After each reset of RESET_TYPE_4 these
coefficients are downloaded from NVM into the corresponding registers. The user may not take care about the
configuration of these parameters. After this has been done, the values are used for the correction procedure.
The figure below shows the formula performed by the calibration unit and the required
sfr
-Register to control
its functionality.
The parameters ADC1_CALOFFS_CHx and ADC1_CALGAIN_CHx are stored in a 8 bit, 2th complement
format.The function applied to calculate the calibrated ADC value is
ADC_cal_CHx = (1 + <ADC_CALGAIN_CHx>/256) * ADC_uncal_CHx + <ADC_CALOFFS_CHx>/2