LM75BD Circuit Board Chips Digital temperature sensor and thermal watchdog

LM75BD Circuit Board Chips Digital temperature sensor and thermal watchdog

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; 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 serial I²C-bus

interface. The device also 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 accessed the conversion in process is not interrupted

(i.e., the I²C-bus section is totally independent of the Sigma-Delta converter section) and

accessing the LM75B continuously without waiting at least one conversion time between

communications willnot 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

■ Pin-for-pin replacement for industry standard LM75 and LM75A and offers improved

temperature resolution of 0.125 °C and specification of a single part over power supply

range from 2.8 V to 5.5 V

■ I²C-bus interface with up to 8 devices on the same bus

■ Power supply range from 2.8 V to 5.5 V

■ Temperatures range from −55 °C to +125 °C

■ Frequency range 20 Hz to 400 kHz with bus fault time-out to prevent hanging up the

bus

■ 11-bit ADC that offers a temperature resolution of 0.125 °C

■ Temperature accuracy of:

◆ ±2 °C from −25 °C to +100 °C

◆ ±3 °C from −55 °C to +125 °C

■ Programmable temperature threshold and hysteresis set points

■ Supply current of 1.0 µA in shutdown mode for power conservation

■ Stand-alone operation as thermostat at power-up

■ ESD protection exceeds 4500 V HBM per JESD22-A114, 450 V MM per

JESD22-A115 and 2000 V CDM per JESD22-C101

■ Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

■ Small 8-pin package types: SO8, TSSOP8 and 3 mm × 2 mm XSON8U

3. Applications

■ System thermal management

■ Personal computers

■ Electronics equipment

■ Industrial controllers