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Input Power Connection to Header J1
Refer to Figure 2.0 for input power wiring. Input Power in the
range of 10 – 60 VDC should be connected at header J7. Cirrus-
6 can supply up to 6.0 Amps (still air) to the fan load at 60°C.
Power to the fan load is derated linearly from 6.0 Amps to 4.0
Amps as temperature increases from 60°C to 75°C. Maximum
operating temperature is 75°C.
Fan Connection to Headers J2-J7
Six Fans: Cirrus-6 distributes power to and monitors the
tachometer signals from up to six four-wire fans. Referring to
Figure 2.0, connect the fans to headers J1 through J6. Please
check fan datasheet for color-coded wiring. Fan current at each
fan header must not exceed 4.0 Amps. Total current required by
the fans connected to the Cirrus-6 must not exceed 6.0 Amps.
Less than Six Fans:Through the I2C Bus, each fan header may
be disabled. When disabled, the alarm outputs associated with
that fan header will always show no alarm.
Connection of Dual I2C Bus to Header J12 I2C Bus Speed Command Inputs when Temperature Sensor
based Fan Control is used: When configured for temperature
sensor based fan control, header J12 will accept I2C commands
from either I2C Bus. If a speed control command is given the
Cirrus-6 will automatically switch to I2C based speed control
mode. Temperature sensor based fan control configurations
support all I2C alarm status registers.
Dual I2C Bus: Cirrus-6 uses 3.3 or 5.0 VDC bus operation
selected by the jumper on J10. The SCL (Pin Cx) and SDA (Pin
Dx) total pull-up must be limited to 3 mA and Bus capacitance
limited to 400 pf per the I2C specification. If only one I2C Bus
is required either connection may be used. If two conflicting
commands are given on each Bus at the same time the command
from the Primary Bus will be used (S0 & D0).
Digital Inputs: The Speed input (Pin 4) and the ID inputs (Pins
1 - 3) are internally pulled to 3.3 VDC with 10.0KO resistors.
GND (Pin GND): Ground reference pin for the I2C Busses and
digital inputs. | 
