EMC2112 Datasheet, PDF (40/65 Pages) SMSC Corporation – RPM-Based Linear Fan Controller with Hardware Thermal Shutdown

RPM-Based Linear Fan Controller with Hardware Thermal Shutdown
Datasheet
The Beta Configuration Registers control advanced temperature measurement features for each
External Diode channel. The Beta Configuration Registers are software locked. The External Diode 1
Beta Configuration register Is hardware locked if the External Diode 1 channel is linked to the hardware
Critical / Thermal shutdown circuitry. Likewise, the External Diode 2 Beta Configuration register is
hardware locked if the External Diode 2 is linked to the Critical / Thermal shutdown circuitry - see
Section 5.9.2.
Bit 4 - AUTO - Enables the Automatic Beta detection algorithm.
„ ‘0’ - The Automatic Beta detection algorithm is disabled. The BETAx[3:0] bit settings will be used
to control the beta compensation circuitry.
„ ‘1’ (default) - The Automatic Beta detection algorithm is enabled. The circuitry will automatically
detect the transistor type and beta values and configure the BETAx[3:0] bits for optimal
performance.
Bits 3 - 0 - BETAx[3:0] - hold a value that corresponds to a range of betas that the Beta Compensation
circuitry can compensate for. These four bits will always show the current beta setting used by the
circuitry. If the AUTO bit is set (default), then these bits may updated by the device with every
temperature conversion. If the AUTO bit is not set, then the value of these bits is used to drive the
beta compensation circuitry. In this case, these bits should be set with a value corresponding to the
lowest expected value of beta for the PNP transistor being used as a temperature sensing device.
See Table 6.11 for supported beta ranges. A value of 1111b indicates that the beta compensation
circuitry is disabled. In this condition, the diode channels will function with default current levels and
will not automatically adjust for beta variation. This mode is used when measuring a discrete 2N3904
transistor or AMD thermal diode.
All of the Beta Configuration Registers are Software Locked.
AUTO
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
0
1
0
1
0
1
0
1
Table 6.11 Beta Compensation
BETAX[3:0]
2
1
0
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
MINIMUM BETA
0.050
0.066
0.087
0.114
0.150
0.197
0.260
0.342
0.449
0.591
0.778
1.024
1.348
1.773
Revision 0.88 (11-20-09)
40
DATASHEET
SMSC EMC2112