VN

Voltage

Regulator

and

Output

Signal

Conditioning

VP

LMT01-SP

Interface

Data

ADC

VREF

Thermal Diode

Analog Circuitry

10

LMT01-SP

SNIS205 – JANUARY 2019

www.ti.com

Product Folder Links: LMT01-SP

Submit Documentation Feedback

Copyright © 2019, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The LMT01-SP 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-SP is regulated by an internal voltage regulator to

The current pulse train output can be converted into a voltage with a single resistor. 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 the device will remain

in a low output state while the LMT01-SP determines the temperature. Once the conversion cycle completes, the

pulse train begins with a pulse frequency of approximately 88 kHz. The LMT01-SP will continuously convert and

transmit data when the power is applied approximately every 104 ms.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Output Interface

The LMT01-SP provides a digital output in the form of a pulse count that is transmitted by a train of current

pulses. After the LMT01-SP is powered up, it transmits a very low current of 34 µA for less than 54 ms while the

part executes a temperature to digital conversion, as shown in Figure 19. When the temperature-to-digital

conversion is complete, the LMT01-SP starts to transmit a pulse train that toggles from the low current of 34 µA

to a high current level of 125 µA. The pulse train total time interval is at maximum 50 ms. The LMT01-SP

transmits a series of pulses equivalent to the pulse count at a given temperature as described in Electrical

Characteristics - Pulse Count to Temperature LUT. After the pulse count has been transmitted the LMT01-SP

current level will remain low for the remainder of the 50 ms. The total time for the temperature to digital

conversion and the pulse train time interval is 104 ms (maximum). If power is continuously applied, the pulse

train output will repeat start every 104 ms (maximum). The LMT01-SP can be powered down at any time to

conserve system power. To avoid invalid data it is recommended that a minimum power-down wait time of 50 ms

is used before the device is turned on again.