EMC1184 datasheet(18/48 Pages) MICROCHIP

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Quad Channel 1°C Temperature Sensor with Beta Compensation and 1.8V SMBus Communications

Datasheet

Revision 1.0 (07-11-13)

SMSC EMC1184

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.

5.1

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.

Figure 5.1 System Diagram for EMC1184

CPU / GPU

EMC1184

Host

DP1

DN1

SMDATA

Thermal

Junction

SMCLK

SMBus

Interface

THERM / ADDR

ALERT / THERM2

Power

Control

VDD

GND

VDD = 3.3V

1.8V – 3.3V

DN2 / DP3

DP2 / DN3

Optional

Anti-parallel

diode

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