EMC2302 datasheet(34/44 Pages) SMSC

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Dual RPM-Based PWM Fan Controller

Datasheet

Revision 1.1 (10-12-09)

SMSC EMC2302

DATASHEET

Bit 5 - NOKICKx - Determines if the Spin Up Routine will drive the fan to 100% duty cycle for 1/4 of

the programmed spin up time before driving it at the programmed level.

‘0’ (default) - The Spin Up Routine will drive the fan driver to 100% for 1/4 of the programmed spin

up time before reverting to the programmed spin level.

‘1’ - The Spin Up Routine will not drive the fan driver to 100%. It will set the drive at the

programmed spin level for the entire duration of the programmed spin up time.

Bits 4 - 2 - SPIN_LVLx[2:0] - Determines the final drive level that is used by the Spin Up Routine as

shown in Table 5.21.

Bit 1 -0 - SPINUP_TIMEx[1:0] - determines the maximum Spin Time that the Spin Up Routine will run

for (see Section 4.6). If a valid tachometer measurement is not detected before the Spin Time has

elapsed, then an interrupt will be generated. When the RPM-based Fan Speed Control Algorithm is

active, the fan driver will attempt to re-start the fan immediately after the end of the last spin up attempt.

The Spin Time is set as shown in Table 5.22.

Table 5.20 DRIVE_FAIL_CNT[1:0] Bit Decode

DRIVE_FAIL_CNTX[1:0]

NUMBER OF UPDATE PERIODS

Disabled - the Drive Fail detection circuitry is disabled (default)

16 - the Drive Fail detection circuitry will count for 16 update

periods

32 - the Drive Fail detection circuitry will count for 32 update

periods

64 - the Drive Fail detection circuitry will count for 64 update

periods

Table 5.21 Spin Level

SPIN_LVLX[2:0]

SPIN UP DRIVE LEVEL

30%

35%

40%

45%

50%

55%

60% (default)

65%

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