SMBus Fan Control with 1°C Accurate Temperature Monitoring
Datasheet
Table 6.13 Ideality Factor Look-Up Table (continued)
SETTING
FACTOR
SETTING
FACTOR
SETTING
FACTOR
0Fh
10h
11h
12h
13h
14h
15h
16h
17h
1.0040
1.0053
1.0066
1.0080
1.0093
1.0106
1.0119
1.0133
1.0146
1Fh
20h
21h
22h
23h
24h
25h
26h
27h
1.0253
1.0267
1.0280
1.0293
1.0306
1.0319
1.0332
1.0345
1.0358
2Fh
30h
31h
32h
33h
34h
35h
36h
37h
1.0462
1.0475
1.0488
1.0501
1.0514
1.0527
1.0540
1.0553
1.0566
6.13
Beta Compensation Register
Table 6.14 Beta Compensation Register
ADDR.
R/W
REGISTER
B7
B6
B5
B4
B3
B2 B1
B0
DEFAULT
18h
R/W
Beta Compensation
-
-
-
-
ENABLE
BETA[2:0]
08h
This register is used to set the Beta Compensation factor that is used for the External Diode channel.
When using a diode-connected transistor (such as the 2N3904) or CPUs that implement the thermal
diode as a two-terminal diode, the CPU compensation circuit must be disabled by writing a value of
07h to this register.
Bit 3 - ENABLE - enables the Beta Compensation Factor Autodetection Algorithm
‘0’ - the Beta Compensation Factor Autodetection circuitry is disabled. The External Diode will
always use the Beta Compensation factor set by the BETA[2:0] bits.
‘1’ (default) - the Beta Compensation Factor Autodetection circuitry is enabled. At the beginning of
every conversion, the circuitry will determine the optimal Beta Compensation factor setting and use
the detected setting. The value of the BETA[2:0] bits will be ignored.
Bit 2-0 - BETA[2:0] - selects the Beta Compensation factor that the External Diode will use if the
autodetection circuitry is disabled. Table 6.15 shows the setting that should be used based on the
expected beta value of the substrate transistor connected to the External Diode channel.
Care should be taken when setting the BETA[2:0] bits. If the Beta Compensation factor is set at a beta
value that is higher than the transistor beta, then the circuit may introduce measurement errors.
Table 6.15 CPU Beta Values
ENABLE
B2
B1
B0
MINIMUM BETA
0.11
0
0
0
0
0
0
0
0
1
0
1
0
0.18
0.25
Revision 2.53 (03-13-07)
SMSC EMC2101
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