Dual Channel 1°C Temperature Sensor with Beta Compensation and 1.8V SMBus Communications
Datasheet
When the THERM pin is asserted, the THERM status bits will likewise be set. Reading these bits will
not clear them until the THERM pin is deasserted. Once the THERM pin is deasserted, the THERM
status bits will be automatically cleared.
5.4.1
THERM Pin Considerations
Because of the decode method used to determine the SMBus Address, it is important that the pull-up
resistance on THERM pin be within ±10% tolerance. Additionally, the pull-up resistor on the THERM
pin must be connected to the same 3.3V supply that drives the VDD pin.
For 15ms after power up, the THERM pin must not be pulled low or the SMBus Address will not be
decoded properly. If the system requirements do not permit these conditions, the THERM pin must be
isolated from the bus during this time. One method of isolating this pin is shown in Figure 5.2.
.
+3.3V
+2.5 - 5V
VDD
DP
1
2
3
8
SMCLK
SMDATA
ALERT
GND
22
K
4.7K -
33
7
K
EMC1182
DN
THERM /
ADDR
6
5
Shared THERM
4
Figure 5.2 Isolating THERM Pin
5.5
ALERT / THERM2 Output
The ALERT / THERM2 pin is an open drain output and requires a pull-up resistor to VDD and has two
modes of operation: interrupt mode and comparator mode. The mode of the ALERT / THERM2 output
is selected via the ALERT / COMPALERT/THERM bit in the Configuration Register (see Section 6.4).
5.5.1
ALERT / THERM2 Pin InterruptALERT Mode
When configured to operate in interrupt mode, the ALERT / THERM2 pin asserts low when an out of
limit measurement (> high limit or < low limit) is detected on any diode or when a diode fault is
detected, functioning as any standard ALERT in on the SMBus. The ALERT / THERM2 pin will remain
asserted as long as an out-of-limit condition remains. Once the out-of-limit condition has been
removed, the ALERT / THERM2 pin will remain asserted until the appropriate status bits are cleared.
The ALERT/ THERM2 pin can be masked by setting the MASK_ALL bit. Once the ALERT / THERM2
pin has been masked, it will be de-asserted and remain de-asserted until the MASK_ALL bit is cleared
by the user. Any interrupt conditions that occur while the ALERT / THERM2 pin is masked will update
the Status Register normally. There are also individual channel masks (see Section 6.10).
The ALERT / THERM2 pin is used as an interrupt signal or as an SMBus Alert signal that allows an
SMBus slave to communicate an error condition to the master. One or more ALERT / THERM2 outputs
can be hard-wired together.
5.5.2
ALERT / THERM2 Pin ComparatorTHERM Mode
When the ALERT / THERM2 pin is configured to operate in comparator mode, it will be asserted if any
of the measured temperatures exceeds the respective high limit, acting as a second THERM function
Revision 1.0 (07-11-13)
20
SMSC EMC1182
DATASHEET
SMSC [ SMSC CORPORATION ]
