Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
6.6
Beta Configuration Registers
Table 6.8 Beta Configuration Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
External Diode 1
Beta
Configuration
14h
R/W
-
-
-
AUTO
BETA1[3:0]
BETA2[3:0]
BETA3[3:0]
10h
External Diode 2
Beta
Configuration
15h
16h
R/W
R/W
-
-
-
-
-
-
AUTO
AUTO
10h
10h
External Diode 3
Beta
Configuration
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 SHDN_SEL pin is not set to disable the Critical
/ Thermal Shutdown functionality (see Table 6.1).
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 6.9 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.
Table 6.9 Beta Compensation Look Up Table
BETAX[3:0]
AUTO
3
2
1
0
MINIMUM BETA
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
1
0
0
1
0
1
0
0.050
0.066
0.087
0.114
0.150
SMSC EMC2104
Revision 1.74 (05-08-08)
DATA5S3HEET
SMSC [ SMSC CORPORATION ]
