EMC6D103 datasheet(70/92 Pages) SMSC

70 / 92 page

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

Datasheet

Revision 0.3 (03-01-07)

SMSC EMC6D103

DATASHEET

Note: The range numbers will be used to calculate the slope of the PWM ramp up. For the fractional

entries, the PWM will go on full when the temp reaches the next integer value e.g., for 3.33,

PWM will be full on at (min. temp + 4).

8.2.18

These registers become read only when the Lock bit is set. Any further attempts to write to these

registers shall have no effect.

Description of OFFx bits:

The OFFx Bits [7:5] specify whether the duty cycle will be set to 0% or the Minimum Fan Duty Cycle

when the measured temperature falls below the Temperature LIMIT register setting. OFF1 applies to

PWM1, OFF2 applies to PWM2, and OFF3 applies to PWM3.

Description of Ramp Rate Control bits:

If the Remote1 or Remote2 pins are connected to a processor or chipset, instantaneous temperature

spikes may be sampled by the part. The auto fan control logic calculates the PWM duty cycle for all

temperature readings. If Ramp Rate Control is disabled, the PWM output will jump or oscillate

between different PWM duty cycles causing the fan to suddenly change speeds, which creates

unwanted fan noise. If enabled, the PWM Ramp Rate Control logic will prevent the PWM output from

jumping, instead the PWM will ramp up/down towards the new duty cycle at a pre-determined ramp

rate.

0111

1000

13.33

1001

1010

1011

26.67

1100

1101

1110

53.33

1111

Table 8.31 Register 62h, 63h: Min/Off, PWM Ramp Rate Control

Address

Read

/Write

Bit 7

(MSb)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

(LSb)

Default

Value

62h

R/W

Min/Off, PWM 1 Ramp

Rate Control

OFF3

OFF2

OFF1

RES

RR1E

RR1-2

RR1-1

RR1-0

00h

63h

R/W

PWM 2, PWM 3 Ramp

Rate Control

RR2E

RR2-2

RR2-1

RR2-0

RR3E

RR3-2

RR3-1

RR3-0

00h

Table 8.32 PWM output below Limit depending on value of Off/Min

OFF/MIN

PWM ACTION

At 0% duty below LIMIT

At Min PWM Duty below LIMIT

Table 8.30 Register Setting vs. Temperature Range (continued)

RAN[3:0]

RANGE (

°C)

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