VDD

R1

LM73

R2

C1

GND

SMBDAT

SMBCLK

VDD

22

LM73-Q1

SNIS194 – DECEMBER 2016

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Product Folder Links: LM73-Q1

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9 Power Supply Recommendations

In systems where there is a large amount of capacitance on the VDD node, the LM73-Q1 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:

1. Allow VDD to reach the specified minimum operating voltage, as specified in the Recommended Operating

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-Q1 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-Q1, it is important to understand that the sensor measures its own die temperature. For the LM73-Q1,

the best thermal path between the die and the outside world is through the LM73-Q1's pins. In the SOT-23

package, all the pins on the LM73-Q1 will have an equal effect on the die temperature. Because the pins

represent a good thermal path to the LM73-Q1 die, the LM73-Q1 will provide an accurate measurement of the

temperature of the printed circuit board on which it is mounted.

10.2 Layout Example

Figure 15. PBC Layout