adm1027 Analog Devices, Inc., adm1027 Datasheet - Page 26

• Manufacturer Part Number: adm1027
• Description: Dbcool? Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

ADM1027
MANUAL FAN SPEED CONTROL MODE
PWM Logic State
The PWM outputs can be programmed to be high for 100%
duty cycle (noninverted) or low for 100% duty cycle (inverted).
PWM1 Configuration (Reg. 0x5C)
<4> INV
PWM2 Configuration (Reg. 0x5D)
<4> INV
PWM3 Configuration (Reg. 0x5E)
<4> INV
PWM Drive Frequency
The PWM drive frequency can be adjusted for the application.
Registers 0x5F to 0x61 configure the PWM frequency for
PWM1 to PWM3, respectively.
PWM1 FREQUENCY REGISTERS (REG. 0x5F to 0x61)
<2:0> FREQ
Manual Fan Speed Control
The ADM1027 allows the duty cycle of any PWM output to be
manually adjusted. This can be useful if you want to change fan
speed in software or want to adjust PWM duty cycle output for
test purposes. Bits <7:5> of Registers 0x5C to 0x5E (PWM
configuration) control the behavior of each PWM output.
0 = logic high for 100% PWM duty cycle
1 = logic low for 100% PWM duty cycle
0 = logic high for 100% PWM duty cycle
1 = logic low for 100% PWM duty cycle
0 = logic high for 100% PWM duty cycle
1 = logic low for 100% PWM duty cycle
000 = 11.0 Hz
001 = 14.7 Hz
010 = 22.1 Hz
011 = 29.4 Hz
100 = 35.3 Hz (default)
101 = 44.1 Hz
110 = 58.8 Hz
111 = 88.2 Hz
–26–
PWM CONFIGURATION (REG. 0x5C to 0x5E)
<7:5> BHVR 111 = Manual Mode
Once under manual control, each PWM output may be manually
updated by writing to Registers 0x30 to 0x32 (PWMx current
duty cycle registers).
Programming the PWM Current Duty Cycle Registers
The PWM current duty cycle registers are 8-bit registers that
allow the PWM duty cycle for each output to be set anywhere
from 0% to 100%. This allows the PWM duty cycle to be set in
steps of 0.39%.
The value to be programmed into the PWM
given by
Example 1: for a PWM duty cycle of 50%,
Value (decimal) = 50/0.39 = 128 decimal
Value = 128 decimal or 80 hex.
Example 2: for a PWM duty cycle of 33%,
Value (decimal) = 33/0.39 = 85 decimal
Value = 85 decimal or 54 hex.
PWM Duty Cycle Registers
Reg. 0x30 PWM1 Duty Cycle = 0xFF (100% default)
Reg. 0x31 PWM2 Duty Cycle = 0xFF (100% default)
Reg. 0x32 PWM3 Duty Cycle = 0xFF (100% default)
By reading the PWMx current duty cycle registers, you can keep
track of the current duty cycle on each PWM output, even when
the fans are running in automatic fan speed control mode or
acoustic enhancement mode.
Value decimal
(
)
=
PWM
MIN
0 39
MIN
.
register is
REV. A