1.

General description

The LM75B is a temperature-to-digital converter using an on-chip band gap temperature

sensor and Sigma-Delta A-to-D conversion technique with an overtemperature detection

output. The LM75B contains a number of data registers: Configuration register (Conf) to

store the device settings such as device operation mode, OS operation mode, OS polarity

and OS fault queue as described in Section 7 “Functional description”; temperature

register (Temp) to store the digital temp reading, and set-point registers (Tos and Thyst) to

store programmable overtemperature shutdown and hysteresis limits, that can be

includes an open-drain output (OS) which becomes active when the temperature exceeds

the programmed limits. There are three selectable logic address pins so that eight devices

can be connected on the same bus without address conflict.

The LM75B can be configured for different operation conditions. It can be set in normal

mode to periodically monitor the ambient temperature, or in shutdown mode to minimize

power consumption. The OS output operates in either of two selectable modes:

OS comparator mode or OS interrupt mode. Its active state can be selected as either

HIGH or LOW. The fault queue that defines the number of consecutive faults in order to

activate the OS output is programmable as well as the set-point limits.

The temperature register always stores an 11-bit 2's complement data giving a

temperature resolution of 0.125

°C. This high temperature resolution is particularly useful

in applications of measuring precisely the thermal drift or runaway. When the LM75B is

independent of the Sigma-Delta converter section) and accessing the LM75B

continuously without waiting at least one conversion time between communications will

not prevent the device from updating the Temp register with a new conversion result. The

new conversion result will be available immediately after the Temp register is updated.

The LM75B powers up in the normal operation mode with the OS in comparator mode,

temperature threshold of 80

°C and hysteresis of 75 °C, so that it can be used as a

stand-alone thermostat with those pre-defined temperature set points.

2.

Features

temperature resolution of 0.125

°C and specification of a single part over power supply

range from 2.8 V to 5.5 V

LM75B

Digital temperature sensor and thermal watchdog

Rev. 02 — 9 December 2008

Product data sheet