1.

General description

The LM75A is a temperature-to-digital converter using an on-chip band gap temperature

sensor and Sigma-delta A-to-D conversion technique. The device is also a thermal

detector providing an overtemperature detection output. The LM75A 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 communicated by a controller via the 2-wire

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 LM75A 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.

The device is powered-up in 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

resolution of 0.125

°C and specification of a single part over power supply range from

2.8 V to 5.5 V

LM75A

Digital temperature sensor and thermal watchdog

Rev. 04 — 10 July 2007

Product data sheet