Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
above VCC or below Ground, they are not diode protected to the power rails. The measured values
are stored in the Reading registers and compared with the Limit registers. The status bits in the
Interrupt Status Register 1 and 2 are set if the measured values violate the programmed limits.
The Vccp voltage input measures the processor voltage, which will lie in the range of 0V to 3.0V.
The following table shows the values of the analog inputs that correspond to the min and max output
codes of the A/D converter. For a complete list of the ADC conversions see Appendix A, "ADC Voltage
Conversion," on page 83.
Table 5.5 Min/Max ADC Conversion Table
INPUT VOLTAGE
+12VIN
+5VIN
VCC/3.3VIN
+2.5VIN
+1.8VIN
+1.5VIN
+VCCP
Min Value (Corresponds
to A/D output 00000000)
<0.062
<0.026
<0.017
<0.013
<0.009
<0.008
<0.012
Max Value (Corresponds
to A/D output 11111111)
>15.938
>6.640
>4.383
>3.320
>2.391
>1.992
>2.988
5.8
5.9
Voltage ID
VID0-VID4 digital inputs are used to store processor Voltage ID codes (for processor operating voltage)
in the VID0-4 register (43h). These VIDs can be read out by the management system using the SMBus
interface.
Temperature Measurement
Temperatures are measured internally by bandgap temperature sensor and externally using two sets
of diode sensor pins (for measuring two external temperatures). See subsections below.
Note: The temperature sensing circuitry for the two remote diode sensors is calibrated for a 3904
type diode.
5.9.1
Internal Temperature Measurement
Internal temperature can be measured by bandgap temperature sensor. The measurement is
converted into digital format by internal ADC. This data is converted in two’s complement format since
both negative and positive temperature can be measured. This value is stored in Internal Temperature
Reading register (26h) and compared to the Temperature Limit registers (50h – 51h). If this value
violates the programmed limits in the Internal High Temperature Limit register (51h) or the Internal Low
Temperature Limit register (50h) the corresponding status bit in Interrupt Status Register 1 is set.
If auto fan option is selected, the hardware will adjust the operation of the fans accordingly. See the
section titled Auto Fan Control Operating Mode on page 30.
5.9.2
External Temperature Measurement
The Hardware Monitor Block also provides a way to measure two external temperatures using diode
sensor pins (Remote x+ and Remote x-). The value is stored in the register (25h) for Remote1+ and
Remote1- pins. The value is stored in the Remote Temperature Reading register (27h) for Remote2+
and Remote2- pins. If these values violate the programmed limits in the associated limit registers, then
the corresponding Remote Diode 1 (D1) or Remote Diode 2 (D2) status bits will be set in the Interrupt
Status Register 1.
If auto fan option is selected, the hardware will adjust the operation of the fans accordingly. See Auto
Fan Control Operating Mode on page 30.
SMSC EMC6D102
Revision 0.4 (06-15-06)
DATA2S5HEET
SMSC [ SMSC CORPORATION ]
