EMC1187 datasheet(17/47 Pages) MICROCHIP

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Triple Channel 1°C Temperature Sensor with Hardware Thermal Shutdown and 1.8V SMBus Communications

Datasheet

SMSC EMC1187

Revision 1.0 (07-11-13)

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

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".

5.2

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.

Figure 5.1 System Diagram for EMC1187

CPU

EMC1187

DP1

DN1

Thermal

diode

DN2

DP2

Host

SMDATA

SMCLK

SMBus

Interface

SYS_SHDN

ALERT

Power

Control

1.8V – 3.3V

VDD

VDD = 3.3V

Internal

Diode

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