Datasheet

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AMC6821

SBAS386C – MAY 2006 – REVISED JULY 2007

In a write operation, the data written are the actual DCY driving the PWM-Out pin in the software DCY control

mode. However, in all other control modes, the data being written are not used to drive the PWM. Instead, it is

stored in a temporary register, and controls the PWM immediately after the control mode is changed to the

software DCY control mode.

Fan Characteristics Register (Address 0x20, Value After Power-On or Reset = 0x1D)

BIT NAME DEFAULT DESCRIPTION

7 FSPD 0 Fan Spin Disable Bit

When FSPD = 1, the fan spin-up process is disabled.

When FSPD = 0, the fan spin-up process is enabled.

6 0 0 Reserved

5 PWM2 0 PWM Frequency Bits

4 PWM1 1 PWM2 PWM1 PWM0 PWM Frequency

3 PWM0 1 When PWM-MODE pin is floating or tied to V

0 0 0 10Hz

0 0 1 15Hz

0 1 0 23Hz

0 1 1 30Hz (Default)

1 0 0 38Hz

1 0 1 47Hz

1 1 0 62Hz

1 1 1 94Hz

When PWM-MODE pin is tied to GND

0 0 0 1kHz

0 0 1 10kHz

0 1 0 20kHz

0 1 1 25kHz (Default)

1 0 0 30kHz

1 0 1 40kHz

1 1 0 40kHz

1 1 1 40kHz

2 STIME2 1 Spin-Up Time Bit

Spin-Up Time

1 STIME1 0

STIME2 STIME1 STIME0 (in Seconds)

0 STIME0 1 0 0 0 0.2

0 0 1 0.4

0 1 0 0.6

0 1 1 0.8

1 0 0 1

1 0 1 2 (Default)

1 1 0 4

1 1 1 8

This register specifies the PWM frequency and the fan spin-up functions.

Product Folder Link(s): AMC6821