ADT7476ARQH ONSEMI [ON Semiconductor], ADT7476ARQH Datasheet - Page 45

• Manufacturer Part Number: ADT7476ARQH
• Description: dBCOOL Remote Thermal Controller and Voltage Monitor
• Manufacturer: ONSEMI [ON Semiconductor]

Enhance Acoustics Register 1 (0x62)
Bit 7 (MIN3) = 0, PWM3 is off (0% PWM duty cycle) when
temperature is below T
Bit 7 (MIN3) = 1, PWM3 runs at PWM3 minimum duty cycle
below T
Bit 6 (MIN2) = 0, PWM2 is off (0% PWM duty cycle) when
temperature is below T
Bit 6 (MIN2) = 1, PWM2 runs at PWM2 minimum duty cycle
below T
Bit 5 (MIN1) = 0, PWM1 is off (0% PWM duty cycle) when
temperature is below T
Bit 5 (MIN1) = 1, PWM1 runs at PWM1 minimum duty cycle
below T
Configuration Register 6 (0x10)
[0] SLOW = 1, slows the ramp rate for PWM changes
associated with the Remote 1 temperature channel by a factor
of 4.
[1] SLOW = 1, slows the ramp rate for PWM changes
associated with the local temperature channel by a factor of 4.
[2] SLOW = 1, slows the ramp rate for PWM changes
associated with the Remote 2 temperature channel by a factor
of 4.
[7] ExtraSlow = 1, slows the ramp rate for all fans by a factor
of 39.2%.
enhanced acoustics is enabled for each temperature channel.
Enhance Acoustics Register 1 (0x62)
[2:0] ACOU selects the ramp rate for PWM outputs
associated with the Remote Temperature 1 input.
Enhance Acoustics Register 2 (0x63)
[2:0] ACOU3 selects the ramp rate for PWM outputs
associated with the local temperature channel.
The following sections list the ramp−up times when
000 = 37.5 sec
001 = 18.8 sec
010 = 12.5 sec
011 = 7.5 sec
100 = 4.7 sec
101 = 3.1 sec
110 = 1.6 sec
111 = 0.8 sec
000 = 37.5 sec
001 = 18.8 sec
010 = 12.5 sec
011 = 7.5 sec
100 = 4.7 sec
101 = 3.1 sec
110 = 1.6 sec
111 = 0.8 sec
MIN
MIN
MIN
− T
− T
− T
HYST
HYST
HYST
.
.
.
MIN
MIN
MIN
− T
− T
− T
HYST
HYST
HYST
.
.
.
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45
[6:4] ACOU2 selects the ramp rate for PWM outputs
associated with the Remote Temperature 2 input.
above ramp rates change to the values below.
Register 6 (0x10) slows the ramp rate further by a factor of 4.
Fan Presence Detect
connected to a PWM output. This feature does not work for
3−wire fans. To detect whether a 4−wire fan is connected
directly to a PWM output, the following must be performed
in this order:
PWM outputs to 100% and then back to its normal speed is
not noticeable in most cases.
How Fan Presence Detect Works
±10%, which typically sources 5 mA. While the detection
cycle is on, an internal current sink is turned on, which sinks
current from the fan’s internal pullup. By driving some of the
current from the fan’s internal pullup (~100 mA) the logic
buffer switches to a defined logic state. If this state is high,
a fan is present; if the state is low, no fan is present.
This ensures the PWM output is not pulled to a voltage
higher than the maximum allowable voltage on that pin
(5.5 V).
When Bit 7 of Configuration Register 6 (0x10) = 1, the
Setting the appropriate slow bit [2:0] of Configuration
This feature is used to determine if a 4−wire fan is directly
As the detection time only takes 5 ms, programming the
4−wire fans typically have an internal pull up to 4.75 V
Note: The PWM input voltage should be clamped to 3.3 V.
000 = 37.5 sec
001 = 18.8 sec
010 = 12.5 sec
011 = 7.5 sec
100 = 4.7 sec
101 = 3.1 sec
110 = 1.6 sec
111 = 0.8 sec
000 = 52.2 sec
001 = 26.1 sec
010 = 17.4 sec
011 = 10.4 sec
100 = 6.5 sec
101 = 4.4 sec
110 = 2.2 sec
111 = 1.1 sec
1. Drive the appropriate PWM outputs to 100%
2. Set Bit 0 of Configuration Register 2 (0x73).
3. Wait 5 ms.
4. Program fans to run at a different speed if necessary.
5. Read the state of Bits [3:1] of Configuration
duty cycle.
Register 2 (0x73). The state of these bits reflects
whether a 4−wire fan is directly connected to the
PWM output.