LM73

SNIS141D – OCTOBER 2005 – REVISED MAY 2009

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FUNCTIONAL DESCRIPTION

The LM73 is a digital temperature sensor that senses the temperature of its die using a sigma-delta analog-to-

digital converter and stores the temperature in the Temperature Register. The LM73's 2-wire serial interface is

The temperature resolution is programmable, allowing the host system to select the optimal configuration

between sensitivity and conversion time. The LM73 can be placed in shutdown to minimize power consumption

when temperature data is not required. While in shutdown, a 1-shot conversion mode allows system control of

the conversion rate for ultimate flexibility.

The LM73 features the following registers. See LM73 REGISTERS for a complete list of the pointer address,

content, and reset state of each register.

1. Pointer Register

2. Temperature Register

3. Configuration Register

6. Control/Status Register

7. Identification Register

POWER-ON RESET

The power-on reset (POR) state is the point at which the supply voltage rises above the power-on reset

threshold (specified in the Electrical Specifications table), generating an internal reset. Each of the registers

contains a defined value upon POR and this data remains there until any of the following occurs:

1. The first temperature conversion is completed, causing the Temperature Register and various status bits to

be updated internally, depending on the value of the measured temperature.

2. The master writes different data to any Read/Write (R/W) bits, or

3. The LM73 is powered down.

ONE-SHOT CONVERSION

The LM73 features a one-shot conversion bit, which is used to initiate a single conversion and comparison cycle

when the LM73 is in shutdown mode. While the LM73 is in shutdown mode, writing a "1" to the One-Shot bit in

the Configuration Register will cause the LM73 to perform a single temperature conversion and update the

Temperature Register and the affected status bits. Operating the LM73 in this one-shot mode allows for

extremely low average-power consumption, making it ideal for low-power applications.

When the One-Shot bit is set, the LM73 initiates a temperature conversion. After this initiation, but before the

completion of the conversion and resultant register updates, the LM73 is in a "one-shot" state. During this state,

the Data Available (DAV) flag in the Control/Status register is "0" and the Temperature Register contains the

value 8000h (-256°C). All other registers contain the data that was present before initiating the one-shot

conversion. After the temperature measurement is complete, the DAV flag will be set to "1" and the temperature

register will contain the resultant measured temperature.

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