EMC2101-R-ACZL-TR datasheet(41/55 Pages) SMSC

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SMBus Fan Control with 1°C Accurate Temperature Monitoring

Datasheet

SMSC EMC2101

Revision 2.53 (03-13-07)

DATASHEET

Note 6.2

When the PWM base clock is set at 360kHz mode 00b is used regardless of the setting

of the TACH_M[1:0] bits.

6.17

Fan Spin Up Configuration Register

The Fan Spin Up Configuration register controls the spin-up behavior of the device. The Fan driver

enters its spin-up routine any time it transitions from a minimum fan setting (00h) to a higher fan setting

(but does not invoke the spin-up routine upon power up). Once the spin-up time has been met, the

fan driver is reduced to the programmed setting.

Bit 5 - FAST_TACH - Determines whether the Spin-Up routine aborts when the measured TACH is less

than the TACH Limit.

‘0’ - The Spin-Up routine uses the duty cycle and spin-up time independently of the TACH reading.

‘1’ (default) - The Spin-Up routine will abort when the TACH measurement is less than the TACH

Limit or the programmed Spin-Up time is met, whichever is less. In this case, the SPIN_DRIVE[1:0]

bits are ignored and the drive will always be at 100%.

APPLICATION NOTE: This bit will be ignored if the ALT_TCH bit in the Configuration Register (see Section 6.5) is

set to ‘0’.

APPLICATION NOTE: If the SPIN_TIME[2:0] bits are set at 000b, then the Spin-Up Routine is bypassed regardless

of the status of this bit.

Bit 4 - 3 SPIN_DRIVE[1:0] - Determines the setting of the drive circuit during the Spin-Up routine

according to Table 6.21.

Table 6.19 TACH Modes

TACH_M[1]

TACH_M[0]

TACH MODE

False readings when under minimum

detectable RPM (TACH Limit).

(Default condition - See Note 6.2)

FFFFh reading when under minimum

detectable RPM.

Table 6.20 Fan Spin Up Configuration Register

ADDR.

R/W

DEFAULT

4Bh

R/W

Fan Spin Up

Config

FAST_

TACH

SPIN_DRIVE[1:0]

SPIN_TIME[2:0]

3Fh

Table 6.21 Spin-Up Drive

SPIN_DRIVE[1:0]

SPIN UP DRIVE

0 - Spin-Up Cycle bypassed

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