EVB-EMC2101 User Manual

3.2EMC2101

The EMC2101 is an SMBus temperature sensor with 1 internal and 1 external sensor in an 8 pin MSOP and 8 pin SOIC package. Communications with the EMC2101 sensor is via the SMBus.

3.3USB to SMBus Bridge

The USB to SMBus bridge is based on an 8051 micro controller with integrated USB and SMBus interfaces as well as internal flash and RAM. During EVB manufacture, firmware is loaded into the bridge that provides the interface between the USB and the SMBus. Power is sourced to the micro controller from the USB interface for device power and communication.

3.3.1Direct SMBus Connect Option

It is also possible to connect an external SMBus master to the EMC2101 EVB. A few jumper settings are all that is required to drive the EMC2101:

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Simply remove the jumpers on JP6 and connect the SMBus master to the SCL, SDA and ALERT pins, as well as an external supply for +3.3V.

The +3.3V can be supplied by the SMBus bridge by leaving the +3.3V jumper in place and retaining the USB connection.

3.4Connecting to Remote Diodes

This EVB is populated with jumpers to connect to an external diode or CPU/GPU. If connecting to a CPU’s thermal diode, it is necessary to provide a common ground. Also, it is usually necessary to bias the appropriate CPU Vcc plane above this common ground to avoid forward-biasing the ESD diodes with the temperature sensor signals. Test point TP3, 8, 10, or 11 provides a ground connection. Consult the CPU manufacturer’s datasheet for guidance on interfacing to the thermal diode. Refer to the schematic EVB-EMC2101 SCH-7069-REVB1.pdf for details on the EVB header connections.

3.5Resistance Error Correction (REC)

The remote diode DN signal path has a 100 ohm series resistor to demonstrate the EMC2101’s REC feature. The resistor may be effectively removed from the circuit by installing a jumper on JP7 or JP13 (-R diode). See Table 3.4 for details on the REC jumper settings.

3.6Power Source

This EVB requires only a USB cable. The USB-SMBus bridge regulates the +5V USB power to +3.3V used by the EMC2101 and other EVB ciruitry such as the fan and resistive heater.

3.7Test Points

Test points are provided for:

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Ground

+3.3V power

+5V_USB power FAN pin output

ALERT output

TACH for 3 wire fan (included)

Revision 1.5 (12-13-06)

SMSC EMC2101

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