AD7879 datasheet(15/36 Pages) AD

Part #	AD7879

Description	Low Voltage Controller for Touch Screens

PDF	36 Pages

Scroll/Zoom	100%

Manufacturer	AD [Analog Devices]

Direct Link	http://www.analog.com

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15 / 36 page

AD7879

Rev. 0 | Page 15 of 36

Temperature Calculations

If an explicit temperature reading in degrees Celsius is required,

calculate for the single measurement method by

Calculate the scale factor of the ADC in degrees per LSB

Degrees per LSB = ADC LSB size/−2.1 mV =

(VCC/4096)/−2.1 mV

Save the ADC output (DCAL) at the calibration

temperature, TCAL.

Take the ADC reading, DAMB, at the temperature to be

measured, TAMB.

Calculate the difference in degrees between TCAL and TAMB by

ΔT = (DAMB − DCAL) × degrees per LSB

Add ΔT to TCAL.

Example

Using VCC = 2.5 V as reference,

Degrees per LSB = (2.5/4096)/−2.1 × 10−3 = −0.291

The ADC output is 983 decimal at 25°C, equivalent to a diode

forward voltage of 0.6 V.

The ADC output at TAMB is 880.

ΔT = (880 − 983) × −0.291 = 30°C

TAMB = 25 + 30 = 55°C

AD7879 Datasheet(PDF) 15 Page - Analog Devices