MAX31785 MAXIM [Maxim Integrated Products], MAX31785 Datasheet - Page 21

• Manufacturer Part Number: MAX31785
• Description: 6-Channel Intelligent Fan Controller
• Manufacturer: MAXIM [Maxim Integrated Products]

Table 5. Device Parametric Monitoring States
For reporting faults/warnings to the host on a real-time
basis, the device asserts the open-drain ALERT pin (if
enabled in MFR_MODE) and sets the appropriate bit in
the various status registers. On recognition of the ALERT
assertion, the host or system manager is expected to poll
the I
The host sends the SMBus ARA (0001 100). The device
ACKs the SMBus ARA, transmits its slave address, and
deasserts ALERT. The system controller then communi-
cates with PMBus commands to retrieve the fault/warn-
ing status information from the device.
See the individual command sections for more details.
Faults and warnings that are latched in the status regis-
ters are cleared when any one of the following conditions
occurs:
• A CLEAR_FAULTS command is received.
• The RST pin is toggled.
• Bias power to the device is removed and then reapplied.
The device responds to fault conditions accord-
ing to the manufacturer fault response command
(MFR_FAULT_RESPONSE). This command byte
determines how the device should respond to each
particular fault. Table 5 illustrates the required con-
ditions and fault actions for specific parameters.
The device uses an internal watchdog timer that is inter-
nally reset every 10ms. In the event that the device is
locked up and this watchdog reset does not occur after
500ms, the device automatically resets. After the reset
occurs, the device reloads all configuration values that
were stored to flash and begins normal operation. After
the reset, the device also does the following:
1) Sets the NONE OF THE ABOVE bit in STATUS_BYTE.
2) Sets the NONE OF THE ABOVE and MFR bits in
3) Sets the WATCHDOG bit in STATUS_MFR_SPECIFIC.
4) Notifies the host through ALERT assertion (if enabled
Overtemperature
STATUS_WORD.
in MFR_MODE).
PARAMETER
Undervoltage
2
Overvoltage
Fan Speed
C bus to determine the device asserting ALERT.
Fault Management and Reporting
Voltage Monitoring Enabled (ADC_ENABLE in MFR_MODE = 1)
Voltage Monitoring Enabled (ADC_ENABLE in MFR_MODE = 1)
Temp Sensor Enabled (ENABLE in MFR_TEMP_SENSOR_CONFIG = 1)
Fan Enabled (Bit 7 in FAN_CONFIG_1_2 = 1)
System Watchdog Timer
6-Channel Intelligent Fan Controller
REQUIRED CONDITIONS FOR ACTIVE MONITORING
The device can monitor up to 11 different temperature
sensors. It can monitor up to four remote I
temperature sensors plus six remote diodes and its own
internal temperature sensor. Each of the enabled temper-
ature sensors is measured once a second. The remote
diode and internal temperature sensors are averaged
eight times to reduce the affect of noise. Each time the
device attempts to read a temperature sensor it checks
for faults. For the remote diode, a fault is defined as
reading greater than +160NC or less than -60NC. For the
internal temperature sensor, a fault is defined as reading
greater than +130NC or less than -60NC. For the I
perature sensors, a fault is defined as a communication
access failure. Temperature sensor faults are reported by
setting the temperature reading to 7FFFh. A temperature
sensor fault results in the setting of the TEMPERATURE
bit in STATUS_BYTE and STATUS_WORD and ALERT is
asserted (if enabled in MFR_MODE). No bits are set in
STATUS_MFR_SPECIFIC.
The temperatures do not have to be used to control the
fan speed. They can be enabled and used for tempera-
ture monitoring only. Reading disabled temperature sen-
sors returns a fixed value of 0000h.
The remote diode temperature sensor can support either
npn or pnp transistors. The device automatically cancels
the series resistance that can affect remote diodes that
are located far from the device.
The device can control up to four DS75LV digital temper-
ature sensors. The A0, A1, and A2 pins on the DS75LV
should be configured as shown in Table 6. The thermo-
stat function on the DS75LV is not used and thus the O.S.
output should be left open circuit.
Table 6. DS75LV Address Pin Configurations
PAGE
10
7
8
9
TEMP SENSOR I
TEMP SENSOR I
TEMP SENSOR I
TEMP SENSOR I
TEMP SENSOR
MAX31785 I
Temperature Sensor Operation
2
2
2
2
2
C
C 0
C 1
C 2
C 3
ACTION DURING A FAULT
DS75LV ADDRESS PIN
Continue Monitoring
Continue Monitoring
Continue Monitoring
Continue Monitoring
A2
0
0
0
0
CONFIGURATION
A1
0
0
1
1
2
C-based
2
C tem-
A0
0
1
0
1
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