PC

Temp

256 C

50 C

4096

§

·

u

q

q

¨

¸

©

¹

Power

Off

54ms

max

Pulse

Train

Start of next

conversion result data

50ms max

End of data

Power

Start of data

transmission

End of data

104ms max

50ms max

Power

ON

11

LMT01-Q1

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SNIS192 – NOVEMBER 2016

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7.3 Feature Description

7.3.1 Output Interface

The LMT01-Q1 provides a digital output in the form of a pulse count that is transmitted by a train of current

pulses. After the LMT01-Q1 is powered up it will transmit 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 15. Once the temperature to digital

conversion has completed the LMT01-Q1 will start 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-Q1 will

transmit a series of pulses equivalent to the pulse count at a given temperature as described in . After the pulse

count has been transmitted the LMT01-Q1 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 (max). If power is

continuously applied the pulse train output will repeat start every 104 ms (max).

Figure 15. Temperature to Digital Pulse Train Timing Cycle

The LMT01LMT01-Q1 can be powered down at any time thus conserving system power. Care should be taken

though, that a power down wait time of 50ms, minimum, be used before the device is turned on again.

7.3.2 Output Transfer Function

The LMT01-Q1 will output at minimum 1 pulse and a theoretical maximum 4095 pulses. Each pulse has a weight

of 0.0625°C. One pulse corresponds to a temperature less than -50°C while a pulse count of 4096 corresponds

to a temperature greater than 200°C. Note that the LMT01-Q1 is only guaranteed to operate up to 150°C.

Exceeding this temperature by more than 5°C may damage the device. The accuracy of the device degrades as

well when 150°C in exceeded.

Two different methods of converting the pulse count to a temperature value will be discussed in this section. The

first method that will be discussed is the least accurate and uses a first order equation. The second method is

the most accurate and uses linear interpolation of the values found in the look-up table (LUT) as described in .

The output transfer function appears to be linear and can be approximated by the following first order equation:

where

•

PC is the Pulse Count

•

Temp is the temperature reading

(1)