EMC6D103 datasheet(67/92 Pages) SMSC

67 / 92 page

Fan Control Device with High Frequency PWM Support and Hardware Monitoring Features

Datasheet

SMSC EMC6D103

Revision 0.3 (03-01-07)

DATASHEET

When in manual control mode, the PWMx Current Duty Cycle Registers (30h-32h) become

Read/Write. It is then possible to control the PWM outputs with software by writing to these

registers. See PWMx Current Duty Cycle Registers description.

When the fan is disabled (100) the corresponding PWM output is driven low (or high, if inverted).

When the fan is Full On (011) the corresponding PWM output is driven high (or low, if inverted).

Notes:

Zone 1 is controlled by Remote Diode 1 Temp Reading register

Zone 2 is controlled by Internal Temp Reading Register

Zone 3 is controlled by Remote Diode 2 Temp Reading register

Bit [4] PWM Invert

Bit [4] inverts the PWM output. If set to 1, 100% duty cycle will yield an output that is low for 255 clocks

and high for 1 clock. If set to 0, 100% duty cycle will yield an output that is high for 255 clocks and

low for 1 clock.

Bit [3] Reserved

Bits [2:0] Spin Up

Bits [2:0] specify the ‘spin up’ time for the fan. When a fan is being started from a stationary state, the

PWM output is held at 100% duty cycle for the time specified in the table below before scaling to a

lower speed. Note: during spin-up, the PWM pin is forced high for the duration of the spin-up time (i.e.,

100% duty cycle = 256/256)

Note: To reduce the spin-up time, this device has implemented a feature referred to as Spin Up

Reduction. Spin Up Reduction uses feedback from the tachometers to determine when each

fan has started spinning properly. Spin up for a PWM will end when the tachometer reading

associated with a PWM must be below min. for spin-up to end prematurely. This feature can

be disabled by clearing bit 4 (SUREN) of the Configuration register (7Fh). If disabled, the all

fans go on full for the duration of their associated spin up time. Note that the Tachx minimum

registers must be programmed to a value less than FFFFh in order for the spin-up reduction

to work properly.

Table 8.26 Fan Zone Setting

ZON[7:5]

PWM CONFIGURATION

000

Fan on zone 1 auto

001

Fan on zone 2 auto

010

Fan on zone 3 auto

011

Fan always on full

100

Fan disabled

101

Fan controlled by hottest of zones 2,3

110

Fan controlled by hottest of zones 1,2,3

111

Fan manually controlled

EMC6D103 Datasheet(PDF) 67 Page - SMSC Corporation

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