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INTERNAL TEMPERATURE SENSOR

Converter

GND

V

DD

+IN

-IN

DV +

kT

q @ ln(N)

(3)

T +

q @ DV

k @ ln(N)

(4)

TSC2007

SBAS405 – MARCH 2007

OVERVIEW (continued)

In some applications, such as battery recharging, an ambient temperature measurement is required. The

temperature measurement technique used in the TSC2007 relies on the characteristics of a semiconductor

versus temperature. The ambient temperature can be predicted in applications by knowing the +25

°C value of

The TSC2007 offers two modes of temperature measurement. The first mode requires calibration at a known

temperature, but only requires a single reading to predict the ambient temperature. The TEMP1 diode, shown in

Figure 22, is used during this measurement cycle. This voltage is typically 580mV at +25

°C with a 10µA current.

voltage is very consistent at –2.1mV/

°C. During the final test of the end product, the diode voltage would be

stored at a known room temperature, in system memory, for calibration purposes by the user. The result is an

equivalent temperature measurement resolution of 0.35

°C/LSB (1LSB = 732µV with V

Figure 22. Functional Block Diagram of Temperature Measurement Mode

The second mode does not require a test temperature calibration, but uses a two-measurement (differential)

method to eliminate the need for absolute temperature calibration and for achieving 2

°C/LSB accuracy. This

mode requires a second conversion of the voltage across the TEMP2 diode with a resistance 80 times larger

than the TEMP1 diode. The voltage difference between the first (TEMP1) and second (TEMP2) conversion is

represented by:

Where:

N = the resistance ratio = 80.

k = Boltzmann's constant = 1.3807

q = the electron charge = 1.6022

T = the temperature in kelvins (K).

This method can provide much improved absolute temperature measurement, but a lower resolution of

1.6

°C/LSB. The resulting equation to solve for T is:

Where:

∆V = V

∴ T = 2.648 ⋅ ∆V (in K)

or T = 2.648

⋅ ∆V – 273 (in °C)

Temperature 1 and temperature 2 measurements have the same timing as Figure 33 and Figure 34.

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