EMC1184 Datasheet, PDF (18/48 Pages) SMSC Corporation – Quad Channel 1°C Temperature Sensor with Beta

Quad Channel 1°C Temperature Sensor with Beta Compensation and 1.8V SMBus Communications
Datasheet
Chapter 5 Product Description
The EMC1184 is an SMBus temperature sensor. The EMC1184 monitors one internal diode and up to
three externally connected temperature diodes.
Thermal management is performed in cooperation with a host device. This consists of the host reading
the temperature data of both the external and internal temperature diodes of the EMC1184 and using
that data to control the speed of one or more fans.
The EMC1184 has two levels of monitoring. The first provides a maskable ALERT / THERM2 signal
to the host when the measured temperatures exceeds user programmable limits. This allows the
EMC1184 to be used as an independent thermal watchdog to warn the host of temperature hot spots
without direct control by the host. The second level of monitoring provides a non-maskable interrupt
on the THERM pin if the measured temperatures meet or exceed a second programmable limit.
For the EMC1184, External Diode channels 2 and 3 are only compatible with general purpose diodes
(such as a 2N3904).
Figure 5.1 shows a system level block diagram of the EMC1184.
CPU / GPU
Thermal
Junction
Optional
Anti-parallel
diode
VDD = 3.3V _{1.8V – 3.3V}
DP1
DN1
VDD
EMC1184
SMCLK
SMDATA
ALERT / THERM2
DP2 / DN3
DN2 / DP3
GND
THERM / ADDR
Host
SMBus
Interface
Power
Control
5.1
Figure 5.1 System Diagram for EMC1184
Modes of Operation
The EMC1184 has two modes of operation.
 Active (Run) - In this mode of operation, the ADC is converting on all temperature channels at the
programmed conversion rate. The temperature data is updated at the end of every conversion and
the limits are checked. In Active mode, writing to the one-shot register will do nothing.
 Standby (Stop) - In this mode of operation, the majority of circuitry is powered down to reduce
supply current. The temperature data is not updated and the limits are not checked. In this mode
of operation, the SMBus is fully active and the part will return requested data. Writing to the one-
shot register will enable the device to update all temperature channels. Once all the channels are
updated, the device will return to the Standby mode.
Revision 1.0 (07-11-13)
18
DATASHEET
SMSC EMC1184