EMC2101-R-ACZL-TR datasheet(39/57 Pages) SMSC

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SMBus Fan Control with 1°C Accurate Temperature Monitoring

Datasheet

SMSC EMC2101

Revision 2.54 (06-16-09)

DATASHEET

6.13

Beta Compensation Register

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.

0Eh

1.0027

1Eh

1.0239

2Eh

1.0449

0Fh

1.0040

1Fh

1.0253

2Fh

1.0462

10h

1.0053

20h

1.0267

30h

1.0475

11h

1.0066

21h

1.0280

31h

1.0488

12h

1.0080

22h

1.0293

32h

1.0501

13h

1.0093

23h

1.0306

33h

1.0514

14h

1.0106

24h

1.0319

34h

1.0527

15h

1.0119

25h

1.0332

35h

1.0540

16h

1.0133

26h

1.0345

36h

1.0553

17h

1.0146

27h

1.0358

37h

1.0566

Table 6.14 Beta Compensation Register

ADDR.

R/W

DEFAULT

18h

R/W

Beta Compensation

ENABLE

BETA[2:0]

08h

Table 6.13 Ideality Factor Look-Up Table (continued)

SETTING

FACTOR

SETTING

FACTOR

SETTING

FACTOR

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