Fan Control Device with High Frequency PWM and Temperature Monitors
Datasheet
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.
Table 6.5, "Min/Max ADC Conversion 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 78.
Table 6.5 Min/Max ADC Conversion Table
INPUT VOLTAGE
VCC
+VCCP
Min Value (Corresponds to A/D output 00000000)
Max Value (Corresponds to A/D output 11111111)
<0.017
>4.383
<0.012
>2.988
6.8
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.
6.8.1
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 31.
6.8.2
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 31.
There are Remote Diode (1 or 2) Fault status bits in Interrupt Status Register 2 (42h), which, when set
to a logical ‘1’, indicate a short or open-circuit on remote thermal diode inputs (Remote x+ and Remote
x-). Before a remote diode conversion is updated, the status of the remote diode is checked. In the
case of a short or open-circuit on the remote thermal diode inputs, the value in the corresponding
reading register will be forced to 80h. Note that this will cause the associated remote diode limit
exceeded status bit to be set (i.e. Remote Diode x Limit Error bits (D1 and D2) are located in the
Interrupt Status 1 Register at register address 41h).
SMSC EMC2300
Revision 0.2 (06-14-06)
DATA2S7HEET
SMSC [ SMSC CORPORATION ]
