SMSC EVB-EMC1002 - Manual (Page 8)

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.
4.4 Fan Driver
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.
4.5 SMBus Alert Protocol (ARA) Support
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.
4.6 Resistance Error Correction (R.E.C.)
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.
4.7 Ideality Factor Correction
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.
4.8 Anti-Parallel Diode (EMC1033 only)
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.