Intel E2180 Design Guide - Page 115

Combining Thermistor and On-Die Thermal, Sensor Control, Interaction of Thermal Profile and T

Page 115 highlights

Legacy Fan Speed Control E.3 Combining Thermistor and On-Die Thermal Sensor Control There is no closed loop control between the FSC and the thermistor, but they work in tandem to provide the maximum fan speed reduction. As discussed in Section E.1.1, the thermistor establishes the VSF curve. This curve will determine the maximum fan speed as a function of the ambient temperature and by design provides a ΨCA sufficient to meet the thermal profile. The FSC, by measuring the processor on-die thermal sensor will command the fan to reduce speed below the VSF curve in response to processor workload. Conversely if the processor workload increases the FSC will command the fan via the PWM duty cycle to accelerate the fan up to the limit imposed by the VSF curve. Figure 7-43. On-Die Thermal Sensor and Thermistor Full Speed Variable Speed Fan (VSF) Curve 100 % Fan Speed (RPM) Fan Speed (% PWM Duty Cycle) Min. Operating Fan Speed Operating Range with FSC Min % E.4 30 34 38 Inlet Temperature (°C) Interaction of Thermal Profile and TCONTROL The processor thermal specification is comprised of the two parameters, TCONTROL and Thermal Profile. The minimum requirement for thermal compliance is to ensure the thermal solution, by design, meets the thermal profile. If the system design will incorporate acoustic speed fan control, Intel requires monitoring the on-die thermal sensor to implement acoustic fan speed control. The value of the on-die thermal sensor temperature determines which specification must be met. • On-die Thermal Sensor less than TCONTROL ⎯ When the thermal solution can maintain the thermal sensor temperature to less than TCONTROL then the fan speed can be reduced. • On-die Thermal Sensor greater than TCONTROL ⎯ The TC must be maintained at or below the Thermal Profile for the measured power dissipation. Thermal and Mechanical Design Guidelines 115

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
  • 51
  • 52
  • 53
  • 54
  • 55
  • 56
  • 57
  • 58
  • 59
  • 60
  • 61
  • 62
  • 63
  • 64
  • 65
  • 66
  • 67
  • 68
  • 69
  • 70
  • 71
  • 72
  • 73
  • 74
  • 75
  • 76
  • 77
  • 78
  • 79
  • 80
  • 81
  • 82
  • 83
  • 84
  • 85
  • 86
  • 87
  • 88
  • 89
  • 90
  • 91
  • 92
  • 93
  • 94
  • 95
  • 96
  • 97
  • 98
  • 99
  • 100
  • 101
  • 102
  • 103
  • 104
  • 105
  • 106
  • 107
  • 108
  • 109
  • 110
  • 111
  • 112
  • 113
  • 114
  • 115
  • 116
  • 117
  • 118
  • 119
  • 120
  • 121
  • 122
  • 123
  • 124
  • 125
  • 126
  • 127
  • 128
  • 129
  • 130
  • 131
  • 132
  • 133
  • 134
  • 135
  • 136
  • 137
  • 138
  • 139
  • 140
  • 141
  • 142
  • 143
  • 144
  • 145
  • 146
  • 147
  • 148

Legacy Fan Speed Control
Thermal and Mechanical Design Guidelines
115
E.3
Combining Thermistor and On-Die Thermal
Sensor Control
There is no closed loop control between the FSC and the thermistor, but they work in
tandem to provide the maximum fan speed reduction. As discussed in Section
E.1.1,
the thermistor establishes the VSF curve. This curve will determine the maximum fan
speed as a function of the ambient temperature and by design provides a
Ψ
CA
sufficient to meet the thermal profile. The FSC, by measuring the processor on-die
thermal sensor will command the fan to reduce speed below the VSF curve in
response to processor workload. Conversely if the processor workload increases the
FSC will command the fan via the PWM duty cycle to accelerate the fan up to the limit
imposed by the VSF curve.
Figure
7-43. On-Die Thermal Sensor and Thermistor
Fan Speed
(RPM)
Inlet Temperature (°C)
Full
Speed
30
38
Min.
Operating
Variable Speed Fan
(VSF) Curve
Fan Speed
Operating Range
with FSC
34
Min %
Fan Speed
(% PWM Duty Cycle)
100 %
Fan Speed
(RPM)
Inlet Temperature (°C)
Full
Speed
30
38
Min.
Operating
Variable Speed Fan
(VSF) Curve
Fan Speed
Operating Range
with FSC
34
Min %
Fan Speed
(% PWM Duty Cycle)
100 %
E.4
Interaction of Thermal Profile and T
CONTROL
The processor thermal specification is comprised of the two parameters, T
CONTROL
and
Thermal Profile. The minimum requirement for thermal compliance is to ensure the
thermal solution, by design, meets the thermal profile.
If the system design will incorporate acoustic speed fan control, Intel requires
monitoring the on-die thermal sensor to implement acoustic fan speed control. The
value of the on-die thermal sensor temperature determines which specification must
be met.
On-die Thermal Sensor less than T
CONTROL
When the thermal solution can maintain the thermal sensor temperature to
less than T
CONTROL
then the fan speed can be reduced.
On-die Thermal Sensor greater than T
CONTROL
The T
C
must be maintained at or below the Thermal Profile for the measured
power dissipation.