Hardware layout and configuration
UM1855
54/100
DocID027351 Rev 3
2.29.4
STPMS2L for PT100 measurement
PT100 is a resistor with temperature-dependent resistance.
Usually, one of two methods is used for measuring temperature with a temperature-
dependent resistor. In the first method, a known current is driven through the measuring
resistor. The temperature is represented by the voltage measured across the resistor. In the
second method, a known voltage is applied on the resistor and the current flowing through is
measured, representing the temperature. In these methods, either an accurate current
source or an accurate voltage source is required.
With the dual-input measurement with STPMS2L in U4 position, no such accurate current or
voltage sources are required. Instead, a precision shunt resistor is required. One channel of
the STPMS2L measures the voltage across the precise shunt resistor, representing the
current flowing through PT100. The other channel measures the voltage across PT100.
Figure 16. Temperature measurement principle schematic diagram
With voltage across and current through the PT100 resistor, the STM32L476ZGT6
microcontroller computes resistance PT100.
For temperatures lower than +100°C, the temperature is given by the following equation,
where PT100 is resistance of the PT100 resitor and T is temperature in degrees centigrade:
2.29.5 Limitations
Operating voltage must be in the range from 3.2 V to 3.6 V.
2.30 STM32L476ZGT6
current
consumption measurement
STM32L476ZGT6 has a built-in circuit allowing to measure its own current consumption
(IDD) in Run and Low-power modes, except for Shutdown mode.
It is strongly recommended that, the MCU supply voltage (VDD_MCU line) does not exceed
3.3 V. This is because there are components on STM32L476G-EVAL supplied from 3.3 V
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