1°C Temperature Sensor with Beta Compensation
Datasheet
Bit 2-0 - BETAx[2:0] - These bits always reflect the current beta configuration settings. If autodetection
circuitry is enabled, then these bits will be updated automatically and writing to these bits will have no
effect. If the autodetection circuitry is disabled, then these bits will determine the beta configuration
setting that is used for their respective channels.
Care should be taken when setting the BETAx[2:0] bits when the autodetection circuitry is disabled. 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. When measuring a discrete thermal diode (such as
2N3904) or a CPU diode that functions like a discrete thermal diode (such as an AMD processor
diode), then the BETAx[2:0] bits should be set to ‘111b’.
Table 6.16 CPU Beta Values
BETAX[2:0]
HEX
ENABLEX
2
1
0
MINIMUM BETA
0.11
0h
1h
0
0
0
0
0
0
0
0
1
0
0
0
0
1
1
1
1
X
0
0
1
1
0
0
1
1
X
0
1
0
1
0
1
0
1
X
0.18
2h
0.25
3h
0.33
4h
0.43
5h
1.00
6h
2.33
7h
Disabled
Autodetection
8h - Fh
6.14 External Diode Ideality Factor Registers
Table 6.17 Ideality Configuration Registers
ADDR.
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
External Diode
1 Ideality
Factor
27h
R/W
-
-
IDEALITY1[5:0]
IDEALITY2[5:0]
IDEALITY3[5:0]
12h
12h
12h
External Diode
2 Ideality
Factor
28h
31h
R/W
R/W
-
-
-
-
External Diode
3 Ideality
Factor
These registers store the ideality factors that are applied to the external diodes. Table 6.18 defines
each setting and the corresponding ideality factor.
Beta Compensation and Resistance Error Correction automatically correct for most diode ideality
errors, therefore it is not recommended that these settings be updated without consulting SMSC.
SMSC EMC1403/EMC1404
Revision 1.16 (03-15-07)
DATA3S7HEET
SMSC [ SMSC CORPORATION ]
