Datasheet
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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
7 L-TEMP4 0 Low Temperature Bit of Local Sensor
6 L-TEMP3 1 L-TEMP4 L-TEMP3 L-TEMP2 L-TEMP1 L-TEMP0 Low Temp
5 L-TEMP2 0 0 0 0 0 0 0 ° C
4 L-TEMP1 0 0 0 0 0 1 4 ° C
3 L-TEMP0 0 0 0 0 1 0 8 ° C
0 0 0 1 1 12 ° C
... ... ... ... ... ...
0 1 0 0 0 32 ° C (Default)
... ... ... ... ... ...
1 1 1 1 0 120 ° C
1 1 1 1 1 124 ° C
2 L-SLP2 0 Slope Bits of Local Sensor
1 L-SLP1 0 Slope
Temp Range in ° C
0 L-SLP0 1 L-SLP2 L-SLP1 L-SLP0 LSB/ ° C %/ ° C (DCY 33.3% to 100%)
0 0 0 32 12.55 5.31
0 0 1 16 6.27 10.62 (default)
0 1 0 8 3.14 21.25
0 1 1 4 1.57 42.5
1 0 0 2 0.78 85
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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