TLE7809G Datasheet, PDF (16/52 Pages) Infineon Technologies AG – Integrated double low-side switch, high-side/LED driver, hall supply, wake-up inputs and LIN communication with embedded MCU (16kB Flash)

TLE7809G
ADC Measurement Interface
6
ADC Measurement Interface
The SBC measurement interface comprises a battery measurement unit (high voltage input V_{bat_sense}) and an on-
chip temperature sensor. A multiplexer is used to select the desired input channel that is connected to the ADC of
the μC. This multiplexer is controlled via the SPI interface. Also, the reference voltage V_AREF is provided by the
SBC. The V_{bat_sense} input must be protected against voltage transients, like ISO pulses by a resistor in series to
terminal 30.
VBAT_ SENSE
Voltage
Attenuator
Mux
On-Chip
Temperature
Sensor
Mode
Selection
SBC
μC
ADC Driver
Amplifier
VAREF
VA
P2.7
ADC
CA
AGND
Figure 9 Simplified Block Diagram of ADC Measurement Interface
6.1
Voltage Measurement
The input voltage is filtered and scaled down to the input voltage range of the ADC converter. The voltage
measurement output code of the ADC can be calculated using the following equation, where V_SENS is the voltage
at the pin V_{BAT_SENSE} and N the resolution of the ADC:
C_VSENS
=
round
V_{-----S---E---N---S--1-- (2N – 1)}
V_AREF 8
, 0V ≤ V_SENS ≤ V_bat–fs
(1)
The input voltage corresponding to the ADC output code C_VSENS can be calculated with the following equation:
V_SENS
=
-8----^×-----^V----^A---^R---^E---^F-
2^N – 1
×
C
VSENS
(2)
6.1.1 Voltage Measurement Calibration Concept
Best measurement accuracy can be obtained by applying the calibration function:
C_VSENSCAL = round[c₁(C_VSENS – c₀)]
(3)
C_VSENS represents the ADC output code for the analog input voltage at the pin V_{BAT_SENSE}. The correction
coefficients c₁ and c₀ correct for slope variations and offset errors of the measurement transfer function.
During the production test these calibration figures are calculated and stored in the flash memory of the
microcontroller.
Data Sheet
16
Rev. 3.01, 2008-04-15