1. General description

The PCT2075 is a temperature-to-digital converter featuring ?1 ?C accuracy over ?25 ?C

to +100 ?C range. It uses an on-chip band gap temperature sensor and Sigma-Delta

A-to-D conversion technique with an overtemperature detection output that is a drop-in

replacement for other LM75 series thermal sensors. The device 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, set-point registers (Tos and Thyst) to

store programmable overtemperature shutdown and hysteresis limits, and programmable

temperature sensor sampling time Tidle, that can be communicated by a controller via the

2-wire serial I2C-bus Fast-mode Plus interface.

The PCT2075 also includes an open-drain output (OS) which becomes active when the

temperature exceeds the programmed limits. 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 PCT2075 can be configured for different operation conditions. It can be set in normal

mode to periodically monitor the ambient temperature, or in shut-down mode to minimize

power consumption.

The temperature register always stores an 11-bit two’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 device is

accessed the conversion in process is not interrupted (that is, the I2C-bus section is totally

independent of the Sigma-Delta converter section) and accessing the device 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. It is also possible to

read just one of the temperature register bytes without lock-up.

The PCT2075 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. The default

set points can be modified during manufacture and ordered under custom part number.

There are three selectable logic address pins with three logic states so that 27 8-pin

devices or three 6-pin devices can be connected on the same bus without address

conflict.

2. Features and benefits

? Pin-for-pin replacement for LM75 series but allows up to 27 devices on the bus

? Power supply range from 2.7 V to 5.5 V

? Temperatures range from ?55 ?C to +125 ?C

? Frequency range 20 kHz to 1 MHz with SMBus time-out to prevent hanging up the bus

? 1 MHz Fast-mode Plus 30 mA SDA drive allows more devices on the same bus but is

backward compatible to Fast-mode and Standard-mode

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

? Temperature accuracy of:

? ?1 ?C (max.) from ?25 ?C to +100 ?C

? ?2 ?C (max.) from ?55 ?C to +125 ?C

? Programmable temperature threshold and hysteresis set points during operation

? Supply current of <1.0 ?A in shut-down mode for power conservation

? Stand-alone operation as thermostat at power-up

? ESD protection exceeds 2000 V HBM per JESD22-A114 and 1000 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 2 mm ? 3 mm HWSON8

? Small 6-pin package type: TSOP6

3. Applications

? System thermal management

? Personal computers

? Electronics equipment

? Industrial controllers

? Cooling system: turn on when the temperature is higher (hotter) than -5?C; turn off

when the temperature is below -10?C