EMC2302 datasheet(31/44 Pages) SMSC

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Dual RPM-Based PWM Fan Controller

Datasheet

SMSC EMC2302

Revision 1.1 (10-12-09)

DATASHEET

Bit 2-0 - UPDATEx[2:0] - 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 5.13.

5.10

Fan Configuration 2 Registers

The Fan Configuration 2 register control the tachometer measurement and advanced features of the

RPM-based Fan Speed Control Algorithm.

Table 5.12 Minimum Edges for Fan Rotation

EDGESX[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 5.13 Update Time

UPDATEX[2:0]

UPDATE TIME

100ms

200ms

300ms

400ms (default)

500ms

800ms

1200ms

1600ms

Table 5.14 Fan Configuration 2 Registers

ADDR

R/W

DEFAULT

33h

R/W

Fan 1

Configuration 2

EN_

RRC1

GLITCH_

EN1

DER_OPT1 [1:0]

ERR_RNG1[1:0]

28h

43h

R/W

Fan 2

Configuration 2

EN_

RRC2

GLITCH_

EN2

DER_OPT2 [1:0]

ERR_RNG2[1:0]

28h

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