EVAL-ADT7475EB ON Semiconductor, EVAL-ADT7475EB Datasheet - Page 17

• 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

actually being measured, exceeding the limit indicates a
slow or stalled fan.
Fan Limit Registers
Register 0x54, TACH1 Minimum Low Byte = 0xFF default
Register 0x55, TACH1 Minimum High Byte = 0xFF default
Register 0x56, TACH2 Minimum Low Byte = 0xFF default
Register 0x57, TACH2 Minimum High Byte = 0xFF default
Register 0x58, TACH3 Minimum Low Byte = 0xFF default
Register 0x59, TACH3 Minimum High Byte = 0xFF default
Register 0x5A, TACH4 Minimum Low Byte = 0xFF default
Register 0x5B, TACH4 Minimum High Byte = 0xFF default
Out−of−Limit Comparisons
be enabled for monitoring. The ADT7475 measures all
voltage and temperature measurements in round−robin
format and sets the appropriate status bit for out−of−limit
conditions. TACH measurements are not part of this
round−robin cycle. Comparisons are done differently,
depending on whether the measured value is being
compared to a high or low limit.
comparator for error detecting and, therefore, have high and
low limits. Fan speed measurements use only a low limit.
This fan limit is needed only in manual fan control mode.
Analog Monitoring Cycle Time
the start bit (Bit 0) of Configuration Register 1 (0x40).
By default, the ADT7475 powers up with this bit set. The
ADC measures each analog input in turn and, as each
measurement is completed, the result is automatically
stored in the appropriate value register. This round−robin
monitoring cycle continues unless disabled by writing a 0 to
Bit 0 of Configuration Register 1.
time taken to monitor all the analog inputs is normally not
of interest, because the most recently measured value of any
input can be read out at any time.
important, it can easily be calculated. The total number of
channels measured is
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•
•
•
conversions. The total monitoring cycle time for averaged
voltage and temperature monitoring is 146 ms. The total
monitoring cycle time for voltage and temperature
monitoring with averaging disabled is 19 ms. The ADT7475
Once all limits have been programmed, the ADT7475 can
Voltage and temperature channels use a window
The analog monitoring cycle begins when a 1 is written to
As the ADC is normally left to free−run in this manner, the
For applications where the monitoring cycle time is
As mentioned previously, the ADC performs round−robin
One dedicated supply voltage input (V
Supply voltage (V
Local temperature
Two remote temperatures
High Limit > Comparison Performed
Low Limit ≤ Comparison Performed
CC
pin)
CCP
pin)
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is a derivative of the ADT7467. As a result, the total
conversion time in the ADT7475 is the same as the total
conversion time of the ADT7467.
synchronized with the analog measurements in any way.
Interrupt Status Registers
Status Register 1 and Interrupt Status Register 2. The status
register bit for each channel reflects the status of the last
measurement and limit comparison on that channel. If a
measurement is within limits, the corresponding status register
bit is cleared to 0. If the measurement is out−of−limits, the
corresponding status register bit is set to 1.
polled by reading the status registers over the serial bus. In
Bit 7 (OOL) of Interrupt Status Register 1 (0x41), 1 means
that an out−of−limit event has been flagged in Interrupt
Status Register 2. This means that the user needs only to read
Interrupt Status Register 2 when this bit is set. Alternatively,
Pin 5 or Pin 9 can be configured as an SMBALERT output.
This automatically notifies the system supervisor of an
out−of−limit condition. Reading the status registers clears
the appropriate status bit as long as the error condition that
caused the interrupt has cleared.
indicating an out−of−limit condition, it remains set even if
the event that caused it has gone away (until read). The only
way to clear the status bit is to read the status register after
the event has gone away. Interrupt status mask registers
(0x74 and 0x75) allow individual interrupt sources to be
masked from causing an SMBALERT. However, if one of
these masked interrupt sources goes out−of−limit, its
associated status bit is set in the interrupt status registers.
Interrupt Status Register 1 (0x41)
Bit 7 (OOL) = 1, denotes that a bit in Status Register 2 is set
and that Interrupt Status Register 2 should be read.
Bit 6 (R2T) = 1, Remote 2 temperature high or low limit has
been exceeded.
Bit 5 (LT) = 1, local temperature high or low limit has been
exceeded.
Bit 4 (R1T) = 1, Remote 1 temperature high or low limit has
been exceeded.
Bit 2 (V
Bit 1 (V
Interrupt Status Register 2 (0x42)
Bit 7 (D2) = 1, indicates an open or short on D2+/D2– inputs.
Bit 6 (D1) = 1, indicates an open or short on D1+/D1– inputs.
Bit 5 (F4P) = 1, indicates that Fan 4 has dropped below
minimum speed. Alternatively, indicates that the THERM
limit has been exceeded, if the THERM function is used.
Bit 4 (FAN3) = 1, indicates that Fan 3 has dropped below
minimum speed.
Fan TACH measurements are made in parallel and are not
The results of limit comparisons are stored in Interrupt
The state of the various measurement channels can be
Status register bits are sticky. Whenever a status bit is set,
CCP
CC
) = 1, V
) = 1, V
CC
CCP
high or low limit has been exceeded.
high or low limit has been exceeded.