EVAL-ADT7475EB ON Semiconductor, EVAL-ADT7475EB Datasheet - Page 26

• Manufacturer Part Number: EVAL-ADT7475EB
• Description: BOARD EVALUATION FOR ADT7475
• Manufacturer: ON Semiconductor
• Series: dBCool®r
• Type: Temperature Sensorr

Specifications of EVAL-ADT7475EB

• Contents: Evaluation Board
• For Use With/related Products: ADT7475
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

PWM Configuration Registers (0x5C to 0x5E)
Bits [7:5] BHVR
manually updated by writing to Register 0x30 to Register
0x32 (PWMx current duty cycle registers).
Programming the PWM Current Duty Cycle Registers
that allow the PWM duty cycle for each output to be set
anywhere from 0% to 100% in steps of 0.39%.
given by:
Example 1: For a PWM duty cycle of 50%,
Example 2: For a PWM duty cycle of 33%,
PWM Current Duty Cycle Registers
Register 0x30, PWM1 Current Duty Cycle = 0x00
(0% default)
Register 0x31, PWM2 Current Duty Cycle = 0x00
(0% default)
Register 0x32, PWM3 Current Duty Cycle = 0x00
(0% default)
user 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. See the
Programming the Automatic Fan Speed Control Loop
section for details.
Operating from 3.3 V Standby
from a 3.3 V STBY supply. In computers that support S3 and
S5 states, the core voltage of the processor is lowered in
these states. When monitoring THERM, the THERM timer
should be disabled during these states.
Standby Mode
the STBY supply. In computers that support S3 and S5 states,
the core voltage of the processor is lowered in these states.
When monitoring THERM, the THERM timer should be
disabled during these states.
the following occurs:
limit, everything is re−enabled and the system resumes
normal operation.
Once under manual control, each PWM output can be
The PWM current duty cycle registers are 8−bit registers
The value to be programmed into the PWM
By reading the PWMx current duty cycle registers, the
The ADT7475 has been specifically designed to operate
The ADT7475 has been specifically designed to respond to
When the V
Once the core voltage, V
111 = manual mode.
Value (decimal) = PWM
Value (decimal) = 50/0.39 = 128 (decimal)
Value = 128 (decimal) or 0x80 (hex)
Value (decimal) = 33/0.39 = 85 (decimal)
Value = 85 (decimal) or 0x54 (hex)
1. Status Bit 1 (V
2. SMBALERT is generated, if enabled.
3. THERM monitoring is disabled. The THERM timer
should hold its value prior to the S3 or S5 state.
CCP
voltage drops below the V
CCP
) in Status Register 1 is set.
CCP
MIN
, goes above the V
/0.39
CCP
MIN
low limit,
register is
CCP
http://onsemi.com
low
26
XNOR Tree Test Mode
mode is useful for in−circuit test equipment at board−level
testing. By applying stimulus to the pins included in the
XNOR tree, it is possible to detect opens or shorts on the
system board.
tree test mode. The XNOR tree test is invoked by setting Bit 0
(XEN) of the XNOR tree test enable register (0x6F).
Power−On Default
input.
is not powered up), the ADT7475 assumes the functionality
of the default registers after the ADT7475 is addressed via
any valid SMBus transaction.
The ADT7475 includes an XNOR tree test mode. This
Figure 40 shows the signals that are exercised in the XNOR
When the ADT7475 is powered up, it polls the V
If V
Y
Y
AFTER THE FAIL−SAFE TIMEOUT
CCP
FAIL−SAFE TIMER ELAPSES
ADT7475 IS POWERED UP
START FAIL−SAFE TIMER
HAS THE ADT7475 BEEN
HAS THE ADT7475 BEEN
HAS THE ADT7475 BEEN
SMBus TRANSACTION?
SMBus TRANSACTION?
SMBus TRANSACTION?
ACCESSED BY A VALID
ACCESSED BY A VALID
ACCESSED BY A VALID
IS V
ADT7475 NORMALLY
stays below 0.75 V (the system CPU power rail
Figure 41. Power−On Flow Chart
CCP
STARTUP THE
Figure 40. XNOR Tree Test
ABOVE 0.75V?
TACH1
TACH2
TACH3
TACH4
PWM2
PWM3
N
Y
N
Y
N
N
PWM1/XTO
HAS THE ADT7475 BEEN
SMBus TRANSACTION?
ACCESSED BY A VALID
SWITCH OFF FANS
RUNS THE FANS
TO FULL SPEED
CHECK V
Y
CCP
N
CCP