MAX31785ETL+ Maxim Integrated Products, MAX31785ETL+ Datasheet - Page 41

• Manufacturer Part Number: MAX31785ETL+
• Description: Board Mount Temperature Sensors 6Ch Intelligent Fan Controller
• Manufacturer: Maxim Integrated Products

Specifications of MAX31785ETL+

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The MFR_FAN_CONFIG command is used with FAN_CONFIG_1_2 to configure the fan. See the FAN_CONFIG_1_2
description for more details on this command. Table 26 describes the MFR_FAN_CONFIG command.
Table 26. MFR_FAN_CONFIG
15:13
11:10
BIT
12
9
8
DUAL_TACH
BIT NAME
FREQ[2:0]
HYS[1:0]
TACHO
TSFO
6-Channel Intelligent Fan Controller
The FREQ bits set the PWM frequency. Note: The device does not support pulse stretching.
0 = Dual tach functionality is disabled.
1 = Dual tach functionality is enabled.
Note: In dual tachometer applications, it is recommended that the slower tachometer signal be
presented to the TACH pin when TACHSEL = 0.
The HYS bits determine the amount of hysteresis the device uses to determine how far the tem-
perature must fall below the temperature level threshold programmed in the LUT before switch-
ing to the lower PWM/RPM value. The hysteresis should be set lower than the minimum differ-
ence between two adjacent temperature steps. These bits are ignored if automatic fan control is
disabled.
0 = Ramp to 100% PWM duty cycle if temp sensor faults (automatic fan mode) or if no
FAN_COMMAND_1 update occurs (manual fan mode) in any 10s period.
1 = Temp sensor fault or update rate to FAN_COMMAND_1 is ignored. Operate at the last
updated PWM/RPM value.
Note 1: A temp sensor fault is a faulty temperature sensor reading, not an overtemperature fault.
Note 2: In automatic fan mode, if the TSFO bit is set to 1, the device ignores a sensor fault and
uses the remaining assigned temperature sensors (if any) to control the fan PWM duty cycle; or,
if the fan has no available temperature sensors to use, it maintains the last updated PWM/RPM
fan value before the fault occurred.
0 = Ramp fan to 100% PWM duty cycle if fan fault is detected.
1 = Do not ramp fan to 100% PWM duty cycle if fan fault is detected.
Note: If the fan fault is removed after ramping the PWM to 100% duty cycle, normal fan opera-
tion is resumed.
FREQ2
HSY1
0
0
0
0
1
1
1
1
0
0
1
1
FREQ1
0
0
1
1
0
0
1
1
HSY0
0
1
0
1
MEANING
FREQ0
0
1
0
1
0
1
0
1
THERMAL HYSTERESIS (NC)
MFR_FAN_CONFIG (F1h)
PWM FREQUENCY
2
4
6
8
Reserved
Reserved
Reserved
100Hz
150Hz
25kHz
30Hz
50Hz
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