MAX31785ETL+ Maxim Integrated Products, MAX31785ETL+ Datasheet - Page 46

• 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

6-Channel Intelligent Fan Controller
The MFR_FAN_RUN_TIME command returns the number of hours of fan lifetime operation. Once every hour, the device
automatically stores this counter in flash memory. The counter is a 16-bit value that rolls over. The latest stored value
is automatically recalled from flash memory upon device power cycle or RST action or a soft reset. This count can be
reset to zero by writing a sequence of all zeros (0000h), followed by all ones (FFFFh), followed by all zeros (0000h)
within 8ms. This value is not updated when the fan is turned off (0% PWM duty cycle).
The MFR_FAN_PWM_AVG command returns the lifetime average of the fan PWM duty cycle in % duty cycle. This aver-
age is not updated when the fan is turned off (0% PWM duty cycle). When combined with the MFR_FAN_RUN_TIME
information, this duty cycle helps predict the remaining lifetime of the fan. Once every hour, the device automatically
stores this value in flash memory. The 2 data bytes are in DIRECT format. The latest stored value is automatically
recalled from flash memory upon device power cycle or RST action or a soft reset. This count can be reset to zero by
writing a sequence of all zeros (0000h), followed by all ones (FFFFh), followed by all zeros (0000h) within 8ms.
The MFR_FAN_PWM2RPM command is used to configure the table the device uses to drive the fan-health status bits in
the lower nibble of STATUS_FAN_1_2. The table maps four preassigned PWM duty cycles to the expected fan speed
in RPM. Table 30 describes the MFR_FAN_PWM2RPM command.
RPM@PWM: Expected Fan Speed at a Certain PWM Duty Cycle: The expected fan speed at four PWM duty cycles
is used to determine the fan health. The fan speed is set in RPM at each PWM duty-cycle step breakpoint. The valid
fan-speed range is 0 to 32,767 (inclusive). The 2 data bytes are in DIRECT format.
To achieve the best results when using the device,
decouple the V
Use a high-quality, ceramic, surface-mount capacitor
if possible. Surface-mount components minimize lead
inductance, which improves performance, and ceram-
ic capacitors tend to have adequate high-frequency
response for decoupling applications.
46
Table 30. MFR_FAN_PWM2RPM
BYTE NUMBER
6-7
4-5
2-3
0-1
DD
Applications Information
power supply with a 0.1FF capacitor.
RPM@100% PWM
Power-Supply Decoupling
RPM@80% PWM
RPM@60% PWM
RPM@40% PWM
WORD NAME
Expected fan speed for a PWM duty cycle of 100%.
Expected fan speed for a PWM duty cycle of 80%.
Expected fan speed for a PWM duty cycle of 60%.
Expected fan speed for a PWM duty cycle of 40%.
Decouple the REG25 and REG18 regulator outputs using
1FF and 10nF capacitors (one each per output).
MSDA, MSCL, SCL, SDA, FAULT, and ALERT are open-
drain pins and require external pullup resistors con-
nected to V
DD
MEANING
to realize high logic levels.
MFR_FAN_PWM2RPM (F9h)
MFR_FAN_RUN_TIME (F7h)
MFR_FAN_PWM_AVG (F8h)
Open-Drain Pins