EVAL-ADT7475EB ON Semiconductor, EVAL-ADT7475EB Datasheet - Page 45

• Manufacturer Part Number: EVAL-ADT7475EB
• Description: BOARD EVALUATION FOR ADT7475
• Manufacturer: ON Semiconductor
• Series: dBCool®r
• Type: Temperature Sensorr

Specifications of EVAL-ADT7475EB

• Contents: Evaluation Board
• For Use With/related Products: ADT7475
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

1. These registers count the number of 11.11 ms periods (based on an internal 90 kHz clock) that occur between a number of consecutive fan TACH
1. These registers reflect the PWM duty cycle driving each fan at any given time. When in automatic fan speed control mode, the ADT7475
1. This register becomes read−only when the Configuration Register 1 lock bit is set to 1. Any subsequent attempts to write to this register fail.
2. These registers set the maximum PWM duty cycle of the PWM output.
Table 16. Fan Tachometer Reading Registers (Power−On Default = 0x00)
Table 17. Current PWM Duty Cycle Registers (Power−On Default = 0x00)
Table 18. Maximum PWM Duty Cycle Registers (Power−On Default = 0xFF)
Register Address
Register Address
Register Address
pulses (default = 2). The number of TACH pulses used to count can be changed using the TACH pulses per revolution register (0x7B). This allows
the fan speed to be accurately measured. Because a valid fan tachometer reading requires that two bytes be read, the low byte must be read
first. Both the low and high bytes are then frozen until read. At power−on, these registers contain 0x0000 until the first valid fan TACH
measurement is read into these registers. This prevents false interrupts from occurring while the fans are spinning up.
A count of 0xFFFF indicates that a fan is one of the following:
reports the PWM duty cycles back through these registers. The PWM duty cycle values vary according to temperature in automatic fan speed
control mode. During fan startup, these registers report back 0x00. In software mode, the PWM duty cycle outputs can be set to any duty
cycle value by writing to these registers.
• Stalled or blocked (object jamming the fan).
• Failed (internal circuitry destroyed).
• Not populated. (The ADT7475 expects to see a fan connected to each TACH. If a fan is not connected to that TACH, its TACH minimum
• Alternate function, for example, TACH4 reconfigured as a THERM pin.).
high and low bytes should be set to 0xFFFF.)
0x2A
0x2B
0x2C
0x2D
0x2E
0x3A
0x28
0x29
0x2F
0x30
0x31
0x32
0x38
0x39
Read−only
Read−only
Read−only
Read−only
Read−only
Read−only
Read−only
Read−only
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
TACH1 low byte.
TACH1 high byte.
TACH2 low byte.
TACH2 high byte.
TACH3 low byte.
TACH3 high byte.
TACH4 low byte.
TACH4 high byte.
PWM1 current duty cycle (0% to 100% duty cycle = 0x00 to 0xFF).
PWM2 current duty cycle (0% to 100% duty cycle = 0x00 to 0xFF).
PWM3 current duty cycle (0% to 100% duty cycle = 0x00 to 0xFF).
Maximum duty cycle for PWM1 output, default = 100% (0xFF).
Maximum duty cycle for PWM2 output, default = 100% (0xFF).
Maximum duty cycle for PWM3 output, default = 100% (0xFF).
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Description
Description
Description
(Note 1)
(Note 1)
(Notes 1 and 2)