XC3101 Datasheet, PDF (6/13 Pages) Torex Semiconductor – Ultra Small Analog Output Temperature Sensor with Alarm Output Pin

XC3101 Series
■çOPERATIONAL EXPLANATION
A small ratio of the analog output (V_AOUT) of the XC3101 series is fed back to one input of the error amplifier via the voltage
divider formed by the R_1x and R_1y resistances. The error amplifier compares this feedback voltage with the voltage of the
internal temperature sensor that is connected to its other input, and the resulting output signal from the error amplifier drives
the Pch-MOS transistor that is connected between the V_DD and V_AOUT pins. This cycle of events stabilizes the V_AOUT voltage
via negative feedback. The internal temperature sensor is controlled so that the voltage changes on a fixed temperature
slope with respect to changes of ambient temperature, and a voltage with a fixed temperature slope is thereby output from
the analog output (V_AOUT).
By comparing the internal voltage reference –which has a small temperature slope- with the voltage, divided by R_1x and
R_1y, of the analog output (V_AOUT) –which has a fixed temperature slope-, the comparator outputs a voltage that turns the
Nch-MOS transistor ON and OFF. Since this Nch-MOS transistor is connected to the V_DOUT pin, we actually control the alarm
output voltage (V_DOUT).
XC3101 Series
<Analog output>
Due to its fixed temperature slope over the temperature range of -40°C to 100°C, the analog output (V_AOUT) of the
XC3101 series outputs a voltage that varies linearly with changes in ambient temperature. For the XC3101A type, whose
temperature slope is -11.77mV/°C (typical), the analog output voltage at Ta=25°C is 1.6V (typical). The temperature
accuracy by means of the analog output voltage is ±3.5°C.
<Alarm output>
The alarm output (V_DOUT) of the XC3101 series holds the alarm output voltage at Low (V_SS potential) when the ambient
temperature rises and the alarm temperature -a threshold set inside the IC- is exceeded. When the ambient temperature
drops below the alarm temperature by an amount that is bigger than the hysteresis width, the alarm output voltage goes
High (pull-up voltage). The alarm output pin is an Nch open drain output, and thus when using alarm output, connect a
pull-up resistor to pull the voltage up to the desired voltage. If not using alarm output, pull the alarm output pin down to the
VSS potential.
<Input/output capacitor>
To stabilize the operation of the XC3101 series, connect a 0.1μF or higher output capacitor (C_L) between the V_AOUT and V_SS
pins. To stabilize the input power supply, connect a 0.1μF or higher input capacitor (C_IN).
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