EMC2101-R-ACZL-TR datasheet(42/57 Pages) SMSC

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SMBus Fan Control with 1°C Accurate Temperature Monitoring

Datasheet

Revision 2.54 (06-16-09)

SMSC EMC2101

DATASHEET

Bit 1-0 - TACH_M[1:0] - Determines the basic operation of the tachometer input as shown in

Table 6.19.

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

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