ADT7462ACPZ-REEL7 ON Semiconductor, ADT7462ACPZ-REEL7 Datasheet - Page 31

• Manufacturer Part Number: ADT7462ACPZ-REEL7
• Description: IC TEMP/VOLT MONITOR 32-LFCSP
• Manufacturer: ON Semiconductor

Specifications of ADT7462ACPZ-REEL7

• Function: Fan Control, Temp Monitor
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 32-LFCSP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Fan Startup Timeout
up (because it is below running speed), the ADT7462
includes a fan startup timeout function. During this time, the
ADT7462 looks for two TACH pulses. If two TACH pulses
are not detected, an interrupt is generated. Using
Configuration Register 1 (0x01), Bit 4, this functionality can
be changed to spinning the fans for a programmable time
instead of two TACH pulses.
by Bits [2:0] in the PWMx configuration registers.
PWM1 Configuration Register = Register 0x21
PWM2 Configuration Register = Register 0x22
PWM3 Configuration Register = Register 0x23
PWM4 Configuration Register = Register 0x24
PWM Logic State
duty cycle (non−inverted) or low for 100% duty cycle
(inverted). This is programmed for each PWM drive in the
PWMx Configuration Registers using the INV bit (Bit 4).
Low Frequency Mode PWM Drive Frequency
application. The ADT7462 supports both high frequency
and low frequency PWM. High or low frequency PWM
mode is selected in Register 0x02, Bit 2. In high frequency
mode, the PWM drive frequency is always 22.5 kHz and
cannot be changed. Register 0x25 and Register 0x26
configure the PWM frequency in low frequency mode for
PWM1 to PWM4.
PWM Drive Frequency 1 is set using Bits [4:2] of the PWM1
and PWM2 frequency register (0x25).
PWM Drive Frequency 2 is set using Bits [7:5] of the PWM1
and PWM2 frequency register (0x25).
PWM Drive Frequency 3 is set using Bits [4:2] of the PWM3
and PWM4 frequency register (0x26).
Table 22. Fan Startup Timeout
To prevent false interrupts being generated as a fan spins
The startup timeout for each PWM drive is programmed
The PWM outputs can be programmed high for 100%
The PWM drive frequency can be adjusted for the
0 = Active high PWM outputs.
1 = Active low PWM outputs.
Bit Code
000
001
010
100
101
011
110
111
No startup timeout
Startup Timeout
100 ms
250 ms
400 ms
667 ms
32 sec
1 sec
2 sec
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PWM Drive Frequency 4 is set using Bits [7:5] of the PWM3
and PWM4 frequency register (0x26).
Fan Speed Control
modes: automatic and manual.
automatically varied with temperature and without CPU
intervention, after initial parameters are set up. The
advantage of this mode is that if the system hangs, the system
is protected from overheating. The automatic fan speed
control incorporates a feature called dynamic T
calibration. This feature reduces the design effort required
to program the automatic fan speed control loop. For more
information on how to program the automatic fan speed
control loop and dynamic T
Programming the Automatic Fan Speed Control Loop
section.
the duty cycle of any PWM output to be manually adjusted.
This is useful if the user wants to change fan speed in the
software or adjust PWM duty cycle output for test purposes.
Bits [7:5] of Register 0x21 to Register 0x24 (PWM
configuration registers) control the behavior of each PWM
output. Under manual control, each PWM output can be
manually updated by writing to Register 0xAA to Register
0xAD (PWM duty cycle registers).
Programming the PWM Current Duty Cycle Registers
that allow the PWM duty cycle for each output to be set
anywhere from 0% to 100% in steps of 0.39%.
given by:
Example 1: For a PWM duty cycle of 50%,
Example 2: For a PWM duty cycle of 33%,
Table 23. Low Frequency PWM Options
The ADT7462 controls fan speed using two different
In automatic fan speed control mode, fan speed is
In manual fan speed control mode, the ADT7462 allows
The PWM current duty cycle registers are 8−bit registers
The value to be programmed into the PWM
Value (decimal) = PWM
Value (decimal) = 50/0.39 = 128 decimal
Value = 128 decimal or 0x80
Value (decimal) = 33/0.39 = 85 decimal
Value = 84 decimal or 0x54
Bit Code
000
001
010
011
100
101
110
111
MIN
MIN
/0.39
Frequency
14.7 Hz
22.1 Hz
29.4 Hz
35.3 Hz
44.1 Hz
58.8 Hz
88.2 Hz
operation, see the
11 Hz
MIN
register is
MIN