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AMC6821

SBAS386C – MAY 2006 – REVISED JULY 2007

Fan Spin Disable Bit: FSPD

This bit enables or disables the spin-up function.

PWM Frequency Bits: [PWM2:PWM0]

These bits specify the PWM frequency; the high range (1kHz–40kHz) has a default value of 25kHz, and the low

range (10Hz–94Hz) has a default value of 30Hz. The clock frequency is 3.2MHz. The PWM-MODE pin

determines which range is selected. When the PWM mode is tied to ground, the high range is selected;

otherwise, the low range is selected.

Spin-Up Time Bits: [STIME2:STIME0]

These bits specify a predetermined time period, or spin-up time, during which the 100% duty cycle is applied to

start the fan spinning. These bits are ignored when FSPD = 1.

DCY-LOW-TEMP Register (Address 0x21, Value After Power-On or Reset = 0x55, 33.2%)

Bit 7 (MSB)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0 (LSB)

L-DCY 7

L-DCY 6

L-DCY 5

L-DCY 4

L-DCY 3

L-DCY 2

L-DCY 1

L-DCY 0

This register specifies the duty cycle in Auto Temp-Fan Control mode when the control temperature is less than

or equal to the value of the Low-Temp bits in the TEMP-FAN Control Regsiter.

Local TEMP-FAN Control Register (Address 0x24, Value After Power-On or Reset = 0x41)

BIT

NAME

DEFAULT

DESCRIPTION

L-TEMP4

Low Temperature Bit of Local Sensor

L-TEMP3

L-TEMP4

L-TEMP3

L-TEMP2

L-TEMP1

L-TEMP0

Low Temp

L-TEMP2

°C

L-TEMP1

°C

L-TEMP0

°C

...

°C (Default)

...

120

°C

124

°C

L-SLP2

Slope Bits of Local Sensor

L-SLP1

Slope

Temp Range in

°C

L-SLP0

L-SLP2

L-SLP1

L-SLP0

LSB/

°C

(DCY 33.3% to 100%)

12.55

5.31

6.27

10.62 (default)

3.14

21.25

1.57

42.5

0.78

This register specifies the parameters of the local Temperature-Fan Control mode.

Low Temperature Bits: [L-TEMP4:L-TEMP0]

These bits specify the low temperature of the local temperature fan control loop. The calculated duty cycle is

equal to the value of the DCY-LOW-TEMP register when the local temperature is less than or equal to the value

defined by bits [L-TEMP4:L-TEMP0]. Refer to the Auto Temperature Fan Mode section for details.

Slope Bits: [L-SLP2:L-SLP0]

These bits define the increment of the duty cycle when the local temperature rises every 1

°C in the auto local

temperature-fan control.

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