R1

LM73

R2

C1

GND

SMBDAT

SMBCLK

LM73

SNIS141F – OCTOBER 2005 – REVISED OCTOBER 2015

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9 Power Supply Recommendations

In systems where there is a large amount of capacitance on the VDD node, the LM73 power supply ramp-up

time can become excessively long. Slow power-supply ramp times may result in abnormal temperature readings.

A linear power-on-ramp of less than 0.7 V/msec and an exponential ramp with an RC time constant of more than

1.25 msec is categorized as a slow power-supply ramp. To avoid errors, use the power up sequence described

below.

The software reset sequence is as follows:

Conditions section.

2. Write a 1 to the Full Power Down bit, Bit 7 of the Configuration Register, and hold it high for the specified

maximum conversion time for the initial default of 11-bits resolution. This ensures that a complete reset

operation has occurred. See the Temperature Conversion Time specifications within the Temperature-to-

Digital Converter Characteristics for more details.

3. Write a 0 to the Full Power Down bit to restore the LM73 to normal mode.

10 Layout

10.1 Layout Guidelines

To achieve the expected results when measuring temperature with an integrated circuit temperature sensor like

the LM73, it is important to understand that the sensor measures its own die temperature. For the LM73, the best

thermal path between the die and the outside world is through the LM73's pins. In the SOT-23 package, all the

pins on the LM73 will have an equal effect on the die temperature. Because the pins represent a good thermal

path to the LM73 die, the LM73 will provide an accurate measurement of the temperature of the printed circuit

board on which it is mounted.

10.2 Layout Example

Figure 16. PBC Layout

22

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