ADT7467ARQZ-R7 datasheet(56/77 Pages) ONSEMI

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ADT7467

Rev. 3 | Page 56 of 77 | www.onsemi.com

Figure 80 shows the behavior of the PWM output as tempera-

ture varies. As the temperature increases, the fan speed ramps

up. Small drops in temperature do not affect the ramp-up

function because the newly calculated fan speed is higher than

the previous PWM value. Enhanced acoustics mode allows the

PWM output to be made less sensitive to temperature

variations. This is dependent on the ramp rate selected and

programmed into the enhanced acoustics registers.

PWM DUTY CYCLE (%)

RTEMP (°C)

TIME (s)

Figure 80. Fan Reaction to Temperature Variation

in Enhanced Acoustics Mode

Slower Ramp Rates

The ADT7467 can be programmed for much longer ramp times

by slowing the ramp rates. Each ramp rate can be slowed by a

factor of 4.

PWM1 Configuration Register (0x5C)

<3> SLOW, a setting of 1 slows the ramp rate for PWM1 by 4.

PWM2 Configuration Register (0x5D)

<3> SLOW, a setting of 1 slows the ramp rate for PWM2 by 4.

PWM3 Configuration Register (0x5E)

<3> SLOW, a setting of 1 slows the ramp rate for PWM3 by 4.

The following sections list the ramp-up times when the SLOW

bit is set for each PWM output.

Enhanced Acoustics Register 1 (0x62)

<2:0> ACOU selects the ramp rate for PWM1.

000 = 140 sec

001 = 70.4 sec

010 = 47.2 sec

011 = 28 sec

100 = 17.6 sec

101 = 12 sec

110 = 6.4 sec

111 = 3.2 sec

Enhanced Acoustics Register 2 (0x63)

<2:0> ACOU3 selects the ramp rate for PWM3.

000 = 140 sec

001 = 70.4 sec

010 = 47.2 sec

011 = 28 sec

100 = 17.6 sec

101 = 12 sec

110 = 6.4 sec

111 = 3.2 sec

<6:4> ACOU2 selects the ramp rate for PWM2.

000 = 140 sec

001 = 70.4 sec

010 = 47.2 sec

011 = 28 sec

100 = 17.6 sec

101 = 12 sec

110 = 6.4 sec

111 = 3.2 sec

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