EMC2103 datasheet(28/84 Pages) SMSC

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RPM-Based Fan Controller with HW Thermal Shutdown

Datasheet

Revision 0.85 (01-29-08)

SMSC EMC2103

DATASHEET

5.5.1

Programming the RPM Based Fan Speed Control Algorithm

The RPM based Fan Speed Control Algorithm powers-up disabled. The following registers control the

algorithm. The EMC2103 fan control registers are pre-loaded with defaults that will work for a wide

variety of fans so only the TACH Target Register is required to set a fan speed. The other fan control

registers can be used to fine-tune the algorithm behavior based on application requirements.

Note that steps 1 - 7 are optional and need only be performed if the default settings do not provide

the desired fan response.

1. Set the Valid TACH Count Register to maximum number of tach counts to indicate the fan is

spinning.

2. Set the Spin Up Configuration Register to the Spin Up Level and Spin Time desired.

Figure 5.4 RPM based Fan Speed Control Algorithm

S e t TA C H Targ e t

Co u n t

TA C H

Re a d in g =

TA C H

Ta rg e t?

Sp in Up

Re q u ire d

Pe rfo rm Sp in U p

Ro u tin e

M a in ta in F a n D riv e

TA C H

Re a d in g <

TA C H

Ta rg e t?

Re d u c e F a n D riv e

In c re a s e F a n D riv e

M e as ure Fa n S p ee d

Ye s

R a m p R a te C o n tro l

EMC2103 Datasheet(PDF) 28 Page - SMSC Corporation