MAX31785 MAXIM [Maxim Integrated Products], MAX31785 Datasheet - Page 26

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

6-Channel Intelligent Fan Controller
fan’s PWM duty cycle is between 40% and 80%. The
masured fan speed is also compared to the expected
at 100% duty cycle. In the 40% to 80% range, a fan’s
expected fan-speed profile is approximately linear. At
duty cycles outside this range (with the exception of
100%), the shape of the expected fan-speed profile
varies too much between fans, and it is not possible to
predict an expected speed.
Table 8. Fan Health Conditions
26
LOWER NIBBLE OF
STATUS_FAN_1_2
ORANGE
YELLOW
GREEN
RED
FAN_HEALTH_CRITERIA BITS IN
MFR_MODE
00
01
10
11
00
01
10
11
00
01
10
11
—
A fan-health-color bit in STATUS_FANS_1_2 is set based
upon the difference between the measured and expect-
ed fan speed and the FAN_HEALTH_CRITERIA bits in
MFR_MODE, as shown in Table 8. If the fan PWM duty
cycle is less than 40% or between 80% and 100%, a
fan-health color cannot be assigned and all the color
bits are cleared. If the fan is unstable, the YELLOW color
bit is set.
Within 10%
Within 10%
Within 15%
Within 15%
Fan speed is not stable
Between 10% and 15%
Between 10% and 20%
Between 15% and 20%
Between 15% and 25%
Over 15%
Over 20%
Over 20%
Over 25%
MONITORED FAN SPEED VS.
EXPECTED TARGET