ADT7476 Analog Devices, Inc., ADT7476 Datasheet - Page 26

• Manufacturer Part Number: ADT7476
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

ADT7476
For applications in which the monitoring cycle time is important,
it can be calculated easily.
The total number of channels measured is
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•
•
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As mentioned previously, the ADC performs round-robin
conversions and takes 11 ms for each voltage measurement,
12 ms for a local temperature reading, and 39 ms for each
remote temperature reading. The total monitoring cycle time
for averaged voltage and temperature monitoring is, therefore,
nominally
Fan TACH measurements are made in parallel and are not
synchronized with the analog measurements in any way.
STATUS REGISTERS
The results of limit comparisons are stored in Interrupt 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 corres-ponding status register bit is cleared to 0. If
the measurement is out-of-limits, the corresponding status
register bit is set to 1.
The state of the various measurement channels can be 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 also
means that the user needs to read Interrupt Status Register 2.
Alternatively, Pin 10 or Pin 14 can be configured as an SMBALERT
output. This hard interrupt 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. Status register
bits are sticky. Whenever a status bit is set, 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. Interrupt mask registers (Register 0x74
and Register 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.
Four dedicated supply voltage inputs
One supply voltage (V
One local temperature
Two remote temperatures
(5 × 11) + 12 + (2 × 39) = 145 ms
CC
pin)
Rev. B | Page 26 of 72
Interrupt Status Register 1 (0x41)
Bit 7 (OOL) = 1, denotes that a bit in Status Register 2 is set and
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 3 (5 V) = 1, 5 V high or low limit has been exceeded.
Bit 2 (V
Bit 1 (V
Bit 0 (2.5 V) = 1, 2.5 V high or low limit has been exceeded. If
the 2.5 V input is configured as THERM , this bit represents the
status of THERM .
Interrupt Status Register 2 (0x42)
Bit 7 (D2 FAULT) = 1, indicates an open or short on D2+/D2–
inputs.
Bit 6 (D1 FAULT) = 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. Alternatively,
indicates the status of GPIO6.
Bit 4 (FAN3) = 1, indicates that Fan 3 has dropped below
minimum speed.
Bit 3 (FAN2) = 1, indicates that Fan 2 has dropped below
minimum speed.
Bit 2 (FAN1) = 1, indicates that Fan 1 has dropped below
minimum speed.
Bit 1 (OVT) = 1, indicates that a THERM overtemperature limit
has been exceeded.
Bit 0 (12 V/VC) = 1, indicates that a 12 V high or low limit has
been exceeded. If the VID code change function is used, this bit
indicates a change in VID code on the VID0 to VID5 inputs.
SMBALERT Interrupt Behavior
The ADT7476 can be polled for status, or an SMBALERT
interrupt can be generated for out-of-limit conditions. It is
important to note how the SMBALERT output and status bits
behave when writing interrupt handler software.
CC
CCP
) = 1, V
) = 1, V
CC
CCP
high or low limit has been exceeded.
high or low limit has been exceeded.