EMC2103 datasheet(56/84 Pages) SMSC

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RPM-Based Fan Controller with HW Thermal Shutdown

Datasheet

Revision 0.85 (01-29-08)

SMSC EMC2103

DATASHEET

term that is applied to the Actual RPM to achieve the Reported RPM. It should only be applied if the

number of edges measured does not match the number of edges expected based on the number of

poles of the fan (which is fixed for any given fan).

Contact SMSC for recommended settings when using fans with more or less than 2 poles.

Bit 2-0 - UPDATE - determines the base time between fan driver updates. The Update Time, along

with the Fan Step Register, is used to control the ramp rate of the drive response to provide a cleaner

transition of the actual fan operation as the desired fan speed changes. The Update Time is set as

shown in Table 6.32.

6.23

Fan Configuration 2 Register

Table 6.31 Minimum Edges for Fan Rotation

EDGES[1:0]

MINIMUM TACH

EDGES

NUMBER OF FAN POLES

EFFECTIVE TACH

MULTIPLIER (BASED ON 2

POLE FANS)

1 pole

0.5

2 poles (default)

3 poles

1.5

4 poles

Table 6.32 Update Time

UPDATE[2:0]

UPDATE TIME

100ms

200ms

300ms

400ms (default)

500ms

800ms

1200ms

1600ms

Table 6.33 Fan Configuration 2 Register

ADDR

R/W

DEFAULT

43h

R/W

Fan

Configuration

EN_

RRC

GLITCH

_EN

DER_OPT [1:0]

ERR_RNG:0]

38h

EMC2103 Datasheet(PDF) 56 Page - SMSC Corporation

EMC2103 Datasheet(HTML) 56 Page - SMSC Corporation

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