EMC1702 datasheet(39/57 Pages) SMSC

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High-Side Current-Sense and Dual 1°C Temperature Monitor

Datasheet

SMSC EMC1702

Revision 1.2 (09-27-10)

DATASHEET

Bits 3-1 - CALRT[2:0] - Determines the number of consecutive measurements that must have an out-

of-limit condition or diode fault before the ALERT pin is asserted. All temperature channels use this

value to set the respective counters. The bits are decoded as shown in Table 5.14. The default setting

is 1 consecutive out-of-limit conversion.

5.13

Beta Configuration Registers

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

Bit 4 - AUTO - Enables the Beta Compensation factor autodetection function.

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

always use the Beta Compensation factor set by the BETAx[3:0] 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[3:0] bits will be automatically updated to indicate the current setting.

Bit 3-0 - BETA[3:0] - These bits always reflect the current beta configuration settings. If autodetection

circuitry is enabled, these bits will be updated automatically and writing to these bits will have no effect.

If the autodetection circuitry is disabled, these bits will determine the beta configuration setting that is

used for their respective channels.

Care should be taken when setting the BETA1[3:0] 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, 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), the

BETA1[3:0] bits should be set to ‘1111b’.

Table 5.14 Consecutive ALERT / THERM Settings

NUMBER OF CONSECUTIVE OUT-OF-LIMIT

MEASUREMENTS

(default for CALRT[2:0])

(default for CTHRM[2:0])

Table 5.15 Beta Configuration Registers

ADDR.

R/W

DEFAULT

25h

R/W

External

Diode 1 Beta

Configuration

AUTO1

BETA1[3:0]

10h

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