EMC1423 datasheet(39/45 Pages) SMSC

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1°C Temperature Sensor with Hardware Thermal Shutdown

Datasheet

SMSC EMC1423/EMC1424

Revision 1.16 (03-15-07)

DATASHEET

6.14

Beta Configuration Registers

This register is used to set the Beta Compensation factor that is used for the external diode channels.

Bit 3 - ENABLEx - Enables the Beta Compensation factor autodetection function. This function shall

be disabled for External Diode 2.

‘0’ - The Beta Compensation Factor autodetection circuitry is disabled. The External Diode will

always use the Beta Compensation factor set by the BETAx[2:0] bits.

‘1’ (default) - The Beta Compensation factor autodetection circuitry is enabled. At the beginning of

every conversion, the optimal Beta Compensation factor setting will be determined and applied.

The BETAx[2:0] bits will be automatically updated to indicate the current setting.

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 6.15 Consecutive Alert / THERM Settings

NUMBER OF CONSECUTIVE OUT OF LIMIT

MEASUREMENTS

(default for CALRT[2:0])

(default for CTHRM[2:0])

Table 6.16 Beta Configuration Registers

ADDR.

R/W

DEFAULT

26h

R/W

External Diode

2 Beta

Configuration

ENABLE2

BETA2[2:0]

08h for

EMC1423 or

07h for

EMC1424

Table 6.17 CPU Beta Values

HEX

ENABLEX

BETAX[2:0]

MINIMUM BETA

0.11

0.18

EMC1423 Datasheet(PDF) 39 Page - SMSC Corporation

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