Datasheet SM9233, SM9235, SM9236 (Silicon Microstructures) - 10

SM9233/SM9235/SM9236 Series www.si-micro.com
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13.2.4 Digital Temperature Transfer Function
45 An internal temperature sensor measures the chip temperature. The temperature characteristic is linear and is described by the following equation: 131 DT = b1 * TA + b0 The temperature transfer function parameters are as follows: 167 170 Temperature Digital Output Sensitivity / Offset 175
Symbol Temperature [°C] Symbol Value [counts ] Symbol Value Unit
TA,1 -40 DT,OUT,1 -32768 b1 397.2 counts/°C T 169 A,2 125 DT,OUT,2 32767 b0 -16881 counts 0 The typical temperature accuracy at 30 °C is within ± 2 °C. 61
13.3 Voltage Supply
The device is supplied from pin VDD, typically 3.3 V, but it can operate as high as 5 V. From this supply input several internal voltage regulators are generating stabilized voltage levels for analog and digital circuit sections. The different internal voltages are monitored by power-OK diagnostic circuitry. Also a stabilized voltage for the resistive MEMS pressure sensor is derived from VDD. The digital data interface allows to set it into Sleep Mode using a specific command (Enter Sleep Mode), which ensures very low consumption (IVDD,SM) of typically less than 10 µA. Of course, in Sleep Mode no pressure data is acquired. For the I2C command to send the sensor into Sleep Mode see 13.6. To wake-up the sensor to normal operation, the clock input SCL shall be toggled (a rising edge at SCL will wake-up the device).
13.4 Diagnosis Functions 13.4.1 MEMS Sensor Bridge Diagnostics
Internal errors of the MEMS pressure sensor are detected and the STATUS registers can be read via the digital I2C interface.
Bridge Diagnostics
An integrated bridge diagnostic circuit supervises the resistive pressure sensor to detect any of the faults as follows: • Sensor faults: • Short of any of the four bridge resistors of the pressure sensor • Interruption of any of the four of bridge resistors • Wiring faults: • Open connection of any of the bridge supply or signals • Wrong connection of any sensor bridge terminal to either ground or bridge supply

The MEMS sensor bridge diagnostics are active permanently (true background diagnostics) and in case of an error the bridge check fail event is indicated by setting the bit bc_fail in the internal STATUS register.
Bridge Supply Diagnostics
Another diagnostic function checks if the supply to the sensor bridge is in its specified range. Here, in case of a supply error the bit bs_fail in the STATUS register will be set.
13.4.2 Configuration Memory Check
The integrity of data stored in the embedded NVM used as the configuration memory (calibration parameters, device configuration, device ID, etc.) is checked at power-up of the component by calculation of a check sum (CRC). If a check sum error is detected no reliable pressure calculation is possible. Therefore, the sensor remains in idle state, i.e. no pressure data transferred to the output registers DSP_T and DSP_S. In this case the bits STATUS.dsp_s_up and dsp_t_up will never be set.

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DOC # 40DS9202.02
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