adt7476a Analog Devices, Inc., adt7476a Datasheet - Page 63

• Manufacturer Part Number: adt7476a
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

Table 38. PWM Minimum Duty Cycle Registers
Register Address
0x64
0x65
0x66
Bit
[7:0]
1
Table 39. T
Register Address
0x67
0x68
0x69
1
2
Table 40. THERM Limit Registers
Register Address
0x6A
0x6B
0x6C
1
2
Table 41. Temperature/T
Register Address
0x6D
[3:0]
[7:4]
0x6E
[7:4]
1
2
These registers become read-only when the ADT7476A is in automatic fan control mode.
These are the T
These registers become read-only when the Configuration Register 1 lock bit is set. Any further attempts to write to these registers have no effect.
If any temperature measured exceeds its THERM limit, all PWM outputs drive their fans at 100% duty cycle. This is a fail-safe mechanism incorporated to cool the
These registers become read-only when the Configuration Register 1 lock bit is set to 1. Any further attempts to write to these registers have no effect.
Each 4-bit value controls the amount of temperature hysteresis applied to a particular temperature channel. Once the temperature for that channel falls below its
These registers become read-only when the Configuration Register 1 lock bit is set to 1. Any further attempts to write to these registers have no effect.
with temperature according to T
system in the event of a critical overtemperature. It also ensures some level of cooling in the event that software or hardware locks up. If set to 0x80, this feature is
disabled. The PWM output remains at 100% until the temperature drops below THERM limit − hysteresis. If the THERM pin is programmed as an output, exceeding
these limits by 0.25°C can cause the THERM pin to assert low as an output.
T
channel. The hysteresis value chosen also applies to that temperature channel if its THERM limit is exceeded. The PWM output being controlled goes to 100% if the
THERM limit is exceeded and remains at 100% until the temperature drops below THERM – hysteresis. For acoustic reasons, it is recommended that the hysteresis
value not be programmed less than 4°C. Setting the hysteresis value lower than 4°C causes the fan to switch on and off regularly when the temperature is close to T
MIN
value, the fan remains running at PWM
MIN
Name
PWM duty cycle
MIN
Registers
registers for each temperature channel. When the temperature measured exceeds T
R/W
Read/Write
HYSL
HYSR1
Read/Write
HYSR2
1
2
MIN
RANGE
Hysteresis Registers
.
R/W
Read/Write
Read/Write
Read/Write
R/W
Read/Write
R/W
Read/Write
Read/Write
Read/Write
R/W
Read/Write
Read/Write
Read/Write
Description
Remote 1 and local temperature hysteresis.
Local temperature hysteresis. 0°C to 15°C of hysteresis can be applied to the local
temperature AFC control loops.
Remote 1 temperature hysteresis. 0°C to 15°C of hysteresis can be applied to the
Remote 1 temperature AFC control loops.
Remote 2 temperature hysteresis.
Local temperature hysteresis. 0°C to 15°C of hysteresis can be applied to the local
temperature AFC control loops.
1
MIN
1
1
2
2
duty cycle until the temperature = T
1
Description
PWM1 minimum duty cycle.
PWM2 minimum duty cycle.
PWM3 minimum duty cycle.
Description
These bits define the PWM
0x00 = 0% duty cycle (fan off ).
0x40 = 25% duty cycle.
0x80 = 50% duty cycle.
0xFF = 100% duty cycle (fan full speed).
Description
Remote 1 temperature T
Local temperature T
Remote 2 temperature T
Description
Remote 1 THERM limit.
Local THERM limit.
Remote 2 THERM limit.
Rev. 0 | Page 63 of 72
MIN
– hysteresis. Up to 15°C of hysteresis can be assigned to any temperature
MIN
.
MIN
MIN
MIN
.
.
MIN
duty cycle for PWMx.
, the appropriate fan runs at minimum speed and increases
Power-On Default
0x80 (50% duty cycle)
0x80 (50% duty cycle)
0x80 (50% duty cycle)
Power-On Default
Power-On Default
0x64 (100°C)
0x64 (100°C)
0x64 (100°C)
0x5A (90°C)
0x5A (90°C)
0x5A (90°C)
Power-On Default
0x44
0x40
ADT7476A
MIN
.