RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
Table 6.9 Ideality Factor Look-Up Table (continued)
SETTING
FACTOR
16h
17h
1.0133
1.0146
6.7
Beta Configuration Register
Table 6.10 Beta Configuration Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
External Diode 1
Beta
Configuration
AUT
O1
14h
RW
-
-
-
-
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 5.1.1)
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 (EMC2103-2
only) then this register can be written normally. Finally, if External Diode 2 is selected as the hardware
shutdown measurement channel (EMC2103-2 only), then the External Diode 2 Beta Configuration
Register will be read only.
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[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 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 6.11 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.
If the External Diode 3 channel is enabled, it will always use a beta setting of 111b.
The Beta Configuration Registers are Software Locked.
SMSC EMC2103
Revision 0.85 (01-29-08)
DATA4S5HEET
SMSC [ SMSC CORPORATION ]
