EMC2103 datasheet(45/84 Pages) SMSC

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RPM-Based Fan Controller with HW Thermal Shutdown

Datasheet

SMSC EMC2103

Revision 0.85 (01-29-08)

DATASHEET

6.7

Beta Configuration Register

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

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

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.

16h

1.0133

17h

1.0146

Table 6.10 Beta Configuration Register

ADDR

R/W

DEFAULT

14h

External Diode 1

Beta

Configuration

AUT

BETA1[2:0]

10h

15h **

R/W

External Diode 2

Beta

Configuration **

AUT

BETA2[2:0]

10h

Table 6.9 Ideality Factor Look-Up Table (continued)

SETTING

FACTOR

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