RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown
Datasheet
7.8
Beta Configuration Register
Table 7.12 Beta Configuration Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
External Diode 1
Beta
Configuration
AUT
O1
14h
R/W
-
-
-
-
BETA1[2:0]
10h
External Diode 2
Beta
Configuration
AUT
O2
15h
R/W
-
-
-
-
BETA2[2:0]
10h
The Beta Configuration Register controls advanced temperature measurement features of the External
Diode channels.
If External Diode 1 is selected as the hardware shutdown measurement channel (see Section 6.1,
"Critical/Thermal Shutdown") then the External Diode 1 Beta register will be read only. If the internal
diode is selected, then this register can be written normally. Likewise, if the External Diode 2 channel
is selected then this register can be written normally. Finally, if External Diode 2 is selected as the
hardware shutdown measurement channel, then the External Diode 2 Beta Configuration Register will
be read only.
The External Diode 3 channel beta configuration will always be set at 07h (disabled / diode mode).
Writing to a read only register will have no affect. The data will be ignored.
Bit 4 - AUTOx - Enables the Automatic Beta detection algorithm for the External Diode X channel.
‘0’ - The Automatic Beta detection algorithm is disabled. The BETAx[2:0] 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[2:0] bits for optimal
performance.
Bits 2 - 0 - BETAx[2:0] - hold a value that corresponds to a range of betas that the Beta Compensation
circuitry can compensate for. These three bits will always show the current beta setting used by the
circuitry. If the AUTO bit is set (default), then these bits may be overwritten 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 7.13, "Beta Compensation Look Up Table" for supported beta ranges. A value of 111b
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.
The Beta Configuration Registers are Software Locked.
Table 7.13 Beta Compensation Look Up Table
BETAX[2:0]
2
1
0
MINIMUM BETA
0
0
0
0
0
1
< 0.08
< 0.111
Revision 1.2 (10-08-09)
SMSC EMC2113
DATA4S8HEET
SMSC [ SMSC CORPORATION ]
