ADT7460ARQ-REEL ON Semiconductor, ADT7460ARQ-REEL Datasheet - Page 32

• Manufacturer Part Number: ADT7460ARQ-REEL
• Description: IC SENSOR TEMP FAN-CTRL 16QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7460ARQ-REEL

• Rohs Status: RoHS non-compliant
• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 120°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 120°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP

ADT7460
Table 36. PWM1–PWM3 Con
Bit
<2:0>
Disabling Fan Start-Up Timeout
Although fan start-up makes fan spin-ups much quieter than
fixed-time spin-ups, the option exists to use fixed spin-up times.
Bit 5 (FSPDIS) = 1 in Configuration Register 1 (Reg. 0x40)
disables the spin-up for two TACH pulses. Instead, the fan spins
up for the fixed time as selected in Registers 0x5C to 0x5E.
PWM Logic State
The PWM outputs can be programmed high for 100% duty
cycle (noninverted) or low for 100% duty cycle (inverted).
Table 37. PWM1–PWM3 Configuration
(Reg. 0x5C–0x5E) Bits
Bit
<4>
PWM Drive Frequency
The PWM drive frequency can be adjusted for the application.
Registers 0x5F to 0x61 configure the PWM frequency for
PWM1 to PWM3, respectively.
Table 38. PWM1 to PWM3 Frequency Registers
(Reg. 0x5F to 0x61)
Bit
<2:0>
Mnemonic
SPIN
Mnemonic
INV
Mnemonic
FREQ
Description
0 = logic high for 100% PWM duty cycle
1 = logic low for 100% PWM duty cycle
Description
000 = 11.0 Hz
001 = 14.7 Hz
010 = 22.1 Hz
011 = 29.4 Hz
100 = 35.3 Hz (default)
101 = 44.1 Hz
110 = 58.8 Hz
111 = 88.2 Hz
Description
These bits control the start-up timeout
for PWM1.
000 = no start-up timeout
001 = 100 ms
010 = 250 ms (default)
011 = 400 ms
100 = 667 ms
101 = 1 s
110 = 2 s
111 = 4 s
figuration (Reg. 0x5C–0x5E)
Rev. C | Page 32 of 52
Fan Speed Control
The ADT7460 can control fa
The first is automatic fan spe
speed is automatically varied with temperature and without
CPU intervention, once initial parameters are set up. The
advantage of this is that, in the case of the system hanging, th
system is protected from overheating. The automatic fan speed
control incorporates a feature called dynamic T
This feature reduces the design effort required to program the
automati
to program the automatic fan speed control loop and dynamic
T
Fan Speed Control Loop application note
(http://www.analog.com/Uploaded
Files/Application_Notes/331085006AN613_0.pdf).
The second fan speed control method is manual fan speed
control, which is described next.
Manual Fan Speed Control
The ADT7460 allows the duty cycle of any PWM output to be
manually adjusted. This can be useful if you want to change fan
speed in software or if you want to adjust PWM duty cycle
output for test purposes. Bits <7:5> of Registers 0x5C, 0x5E
(PWM configuration) control the behavior of each PWM output.
Table 39. PWM1 to PWM3 Configuration
(Reg. 0x5C–0x5E) Bits
Bit
<7:5>
Once under manual control, each PWM output can be manually
updated by writing to Registers 0x30, 0x32 (PWMx current duty
cycle registers).
Programming the PWM Current Duty Cycle Registers
The PWM current duty cycle registers are 8-bit registers, which
allow the PWM duty cycle for each output to be set anywhere
from 0% (0x00) to 100% (0xFF) in steps of 0.39% (256 steps).
The value to be programmed into the PWMMIN register is
given by
Example 1: For a PWM duty cycle of 50%,
Value (decimal) = 50/0.39 = 128d
Value = 128d or 0x80.
Example 2: For a PWM duty cycle of 33%,
Value (decimal) = 33/0.39 = 85d
Value = 85d or 0x54.
MIN
Value (decimal) = PWM
calibration, see the AN-613 Programming the Automatic
c fan speed control loop. For more information on how
Mnemonic
BHVR 111
n speed by two different modes.
ed control mode. In this mode, fan
MIN
/0.39
Description
Manual mode
MIN
calibration.
e