SMSC EVB-EMC1033 User Manual

EVB-EMC1002/EMC1033 User Manual

Revision 1.1 (12-14-06)

SMSC EMC1002/EMC1033

8

Note: Asserting the 

Addr

/

Therm

 output low will also turn on the ARA LED on this EVB. This is because

the fan driver circuit will pull down the 

Alert/Therm2

 output when 

Addr

/

Therm

 is low. The SMBus

ARA Protocol will not function in this case. 

The fan driver utilizes the 

Alert/Therm2

 and 

Addr

/

Therm

 outputs to drive a +5V fan to 3 different fan

speeds. See the Circuit Description above for information about the fan driver. Normally, the fan driver
is OFF. To turn the fan ON at low speed, the 

Alert/Therm2

 output must be asserted low. This can be

caused by dragging the High Temp Limit line below the current temperature on the Zone Temperature
History graph, using the Register Manager to set the High Temp Limit value lower than the current
temperature or heating the temp sensor to exceed the limit. 

To turn the fan ON to high speed, the 

Addr

/

Therm

 output must be asserted low. This will occur when

the current temperature exceeds the associated THERM limit.

Note: When 

Alert/Therm2

 is configured as a 

Therm2

 output, temperatures exceeding the High Temp

Limit will cause it to assert, however the Low Temp Limit is ignored.

When the 

Alert/Therm2

 output is asserted an SMBus Alert interrupt is generated and an indicator light

will turn RED on the Register Manager panel. Press the Response button to cause RegMan to send
the SMBus Alert Address to the EMC1002/1033. The EMC1002/1033 will respond with it’s SMBus
address which is displayed in a text box next to the Response button on the RegMan interface. If the
temperature is still above the limit, the indicator will remain lit and the 

Alert/Therm2

 output will stay

asserted. If the temperature is below the limit the indicator will turn OFF and the 

Alert/Therm2

 output

will de-assert. 

R.E.C. is normally enabled in the EMC1002/1033, however, for demonstration purposes this evaluation
board uses a special test mode to disable R.E.C. To show the R.E.C. feature, remove the jumper on
JP1 pins 1-2. This will insert a 100 ohm series resistor into the circuit and cause a temperature reading
error of approximately 60

o

C. Replace the jumper and the temperature will return to its correct reading.

Now enable R.E.C. by entering the value 0x0c into R.E.C. configuration register 0x53. With R.E.C.
enabled, the temperature will not change when the jumper is removed. 

The Ideality Factor can be adjusted in Ideality Factor Registers 0x27 and 0x28 (EMC1033 only). These
registers will normally hold the default value which is correct for the diodes installed on the EVB.
Increasing or decreasing the value will cause a corresponding change in the temperature reading. 

The EMC1033 supports an Anti-Parallel Diode (APD) configuration, where 2 diodes share the same
DP and DN lines but are in opposite polarity to each other. The Remote2 diode can be disconnected
from the circuit by removing one or both jumpers on JP1 pins 3-4 and 5-6. The APD function is
normally enabled on device power-up; the function can be disabled by writing a “1” to Configuration
Register 0x09, bit 0.