EMC1187 Datasheet, PDF (17/47 Pages) SMSC Corporation – Triple Channel 1°C Temperature Sensor with Hardware

Triple Channel 1°C Temperature Sensor with Hardware Thermal Shutdown and 1.8V SMBus Communications
Datasheet
Chapter 5 Product Description
The is an SMBus temperature sensor with Hardware Thermal Shutdown. The EMC1187 monitor one
internal diode and up to two 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 EMC1187 and using
that data to control the speed of one or more fans.
The EMC1187 has two levels of monitoring. The first provides a maskable ALERT signal to the host
when the measured temperatures exceeds user programmable limits. This allows the EMC1187 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 asserts the SYS_SHDN pin when the External
Diode temperature exceeds a hardware specified threshold temperature.Additionally, the internal diode
and External Diode 2 can be configured to assert the SYS_SHDN pin when the measured temperature
exceeds user programmable limits.
For the EMC1187, the External Diode 2 channel is compatible with any diode type.
Figure 5.1 shows a system level block diagram of the EMC1187.
5.1
5.2
CPU
Thermal
diode
VDD = 3.3V 1.8V – 3.3V
VDD
EMC1187
DP1
DN1
Internal
Diode
SMCLK
SMDATA
ALERT
DP2
DN2
SYS_SHDN
Host
SMBus
Interface
Power
Control
Figure 5.1 System Diagram for EMC1187
Conversion Rates
The EMC1187 may be configured for different conversion rates based on the system requirements.
The conversion rate is configured as described in Section 6.5. The default conversion rate is 4
conversions per second. Other available conversion rates are shown in Table 6.6, "Conversion Rate".
Dynamic Averaging
Dynamic averaging causes the EMC1187 to measure the external diode channels for an extended time
based on the selected conversion rate. This functionality can be disabled for increased power savings
at the lower conversion rates (see Section 6.4, "Configuration Register 03h / 09h"). When dynamic
averaging is enabled, the device will automatically adjust the sampling and measurement time for the
external diode channels. This allows the device to average 2x or 16x longer than the normal 11 bit
operation (nominally 21ms per channel) while still maintaining the selected conversion rate. The
benefits of dynamic averaging are improved noise rejection due to the longer integration time as well
as less random variation of the temperature measurement.
SMSC EMC1187
17
DATASHEET
Revision 1.0 (07-11-13)