TLE7809G datasheet(16/52 Pages) INFINEON

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TLE7809G

ADC Measurement Interface

Data Sheet

Rev. 3.01, 2008-04-15

ADC Measurement Interface

The SBC measurement interface comprises a battery measurement unit (high voltage input

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

bat_sense input must be protected against voltage transients, like ISO pulses by a resistor in series to

terminal 30.

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

SENS is the voltage

at the pin

BAT_SENSE and N the resolution of the ADC:

(1)

The input voltage corresponding to the ADC output code

VSENS can be calculated with the following equation:

(2)

6.1.1

Voltage Measurement Calibration Concept

Best measurement accuracy can be obtained by applying the calibration function:

(3)

VSENS represents the ADC output code for the analog input voltage at the pin VBAT_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.

VBAT_SENSE

AGND

Voltage

Attenuator

On-Chip

Temperature

Sensor

ADC Driver

Amplifier

Mode

Selection

Mux

ADC

VAREF

P2.7

SBC

μC

CVSENS

round

VSENS

VAREF

----------------1

---2

–

() , 0V VSENS Vbat f

– s

≤≤

VSENS

× AREF

–

-------------------------

VSENS

CVSENSCAL

round c1 CVSENS c0

–

()

[]

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