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The NE1617A is an accurate two-channel temperature monitor. It measures the
temperature of itself and the temperature of a remote sensor. The remote sensor is a
diode-connected transistor. This can be in the form of either a discrete NPN/PNP, such as
the 2N3904/2N3906, or a diode-connected PNP built into another die, such as is done on
some Intel microprocessors.
The temperature of both the remote and local sensors is stored in a register that can be
read via a 2-wire SMBus. The temperatures are updated at a rate that is programmable
via the SMBus (the average supply current is dependent upon the update rate — the
faster the rate, the higher the current).
In addition to the normal operation, which is to update the temperature at the programmed
rate, there is a one-shot mode that will force a temperature update.
There is also an alarm that senses either an overtemperature or under temperature
condition. The trip points for this alarm are also programmable.
The device can have one of nine addresses (determined by two address pins), so there
can be up to nine of the NE1617A on the SMBus.
It can also be put in standby mode (in order to save power). This can be done either with
software (over the SMBus) or with hardware (using the STBY pin).