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.
