SNIS189D June 2015 – June 2018 LMT01
The LMT01 temperature output is transmitted over a single wire using a train of current pulses that typically change from 34 µA to 125 µA. A simple resistor can then be used to convert the current pulses to a voltage. With a 10-kΩ resistor, the output voltage levels range from 340 mV to 1.25 V, typically. A simple microcontroller comparator or external transistor can be used convert this signal to valid logic levels the microcontroller can process properly through a GPIO pin. The temperature can be determined by gating a simple counter on for a specific time interval to count the total number of output pulses. After power is first applied to the device the current level will remain below 34 µA for at most 54 ms while the LMT01 is determining the temperature. When the temperature is determined, the pulse train begins. The individual pulse frequency is typically 88 kHz. The LMT01 will continuously convert and transmit data when the power is applied approximately every 104 ms (maximum).
The LMT01 uses thermal diode analog circuitry to detect the temperature. The temperature signal is then amplified and applied to the input of a ΣΔ ADC that is driven by an internal reference voltage. The ΣΔ ADC output is then processed through the interface circuitry into a digital pulse train. The digital pulse train is then converted to a current pulse train by the output signal conditioning circuitry that includes high and low current regulators. The voltage applied across the pins of the LMT01 is regulated by an internal voltage regulator to provide a consistent Chip VDD that is used by the ADC and its associated circuitry.