Analog Devices dBCool ADT7467 Manual page 71

Table 38. THERM Limit Registers
Register Address
0x6A
0x6B
0x6C
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
1
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, then
exceeding these limits by 0.25°C can cause the THERM pin to assert low as an output.
2 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.
Table 39. Temperature/T
MIN
Register Address
0x6D
<3:0>
<7:4>
0x6E
<7:4>
1 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 T
value, the fan remains running at PWM
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
2 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.
Table 40. XNOR Tree Test Enable
Register Address
0x6F
<0>
<7:1>
1 This register becomes read-only when the Configuration Register 1 lock bit is set to 1. Any further attempts to write to this register have no effect.
Table 41. Remote 1 Temperature Offset
Register Address
0x70
<7:0>
1 This register becomes read-only when the Configuration Register 1 lock bit is set to 1. Any further attempts to write to this register have no effect.
1
2
R/W Description
Remote 1 THERM limit.
Read/write
Read/write Local THERM limit.
Remote 2 THERM limit.
Read/write
1
Hysteresis Registers
2
R/W Description
Read/write Remote 1 and local temperature hysteresis.
HYSL Local temperature hyseresis. 0°C to 15°C of
hysteresis can be applied to the local temperature
AFC and dynamic T
HYSR1 Remote 1 temperature hyseresis. 0°C to 15°C of
hysteresis can be applied to the Remote 1
temperature AFC and dynamic T
Read/write Remote 2 temperature hysteresis.
HYSR2 Local temperature hyseresis. 0°C to 15°C of
hysteresis can be applied to the local temperature
AFC and dynamic T
duty cycle until the temperature = T
MIN
1
R/W Description
Read/write XNOR tree test enable register.
XEN If the XEN bit is set to 1, the device enters the XNOR
tree test mode. Clearing the bit removes the device
from the XNOR tree test mode.
Reserved Unused. Do not write to these bits.
1
R/W Description
Read/write Remote 1 temperature offset.
Read/write Allows a twos complement offset value to be
automatically added to or subtracted from the
Remote 1 temperature reading. This is to
compensate for any inherent system offsets such as
PCB trace resistance. LSB value = 0.5°C.
control loops.
MIN
MIN
control loops.
MIN
– hysteresis. Up to 15°C of hysteresis can be assigned to any temperature channel.
MIN
Rev. 0| Page 71 of 80
Power-On Default
0x64 (100°C)
0x64 (100°C)
0x64 (100°C)
Power-On Default
0x44
control loops.
0x40
Power-On Default
0x00
Power-On Default
0x00
ADT7467
MIN
.
MIN