INTERNAL TEMPERATURE SENSOR

Converter

GND

V

DD

+IN

-

IN

GND

REF

DV +

kT

q @ ln(N)

(3)

T +

q @ DV

k @ ln(N)

(4)

TSC2008

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

temperature measurement technique used in the TSC2008 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 TSC2008 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 23, is used during this measurement cycle. This voltage is typically 580mV at +25°C with a 10

µA current.

voltage is very consistent at –2.1mV/°C. During the final test of the end product, the diode voltage is stored at a

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

temperature measurement resolution of 0.3°C/LSB (1LSB = 610

µV with V

Figure 23. 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 91 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 = 91.

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:

∴ T = 2.573 ⋅ ΔV (in K),

or T = 2.573

⋅ ΔV – 273 (in °C).

Temperature 1 and/or temperature 2 measurements have the same timing as shown in Figure 30 to Figure 33.

14

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