Sensor Based Thermal Specification Design Guidance
8.4.1DTS 1.1 A New Fan Speed Control Algorithm withoutTAMBIENT Data
In most system designs incorporating processor ambient inlet data in fan speed control adds design and validation complexity with a possible BOM cost impact to the system. A new fan speed control methodology is introduced to improve system acoustics without needing the processor inlet ambient information.
The DTS 1.1 implementation consists of two parts, a ΨCA requirement at TCONTROL and a ΨCA point at DTS =
The ΨCA point at DTS =
ΨCA = (TCASE_max - TAmbient target) / TDP
For example, for a 95 TDP part, the Tcase max is 72.6C and at a worst case design point of 40C local ambient this will result in
ΨCA = (72.6 - 40) / 95 = 0.34 C/W
Similarly for a system with a design target of 45 C ambient the ΨCA at DTS =
The second point defines the thermal solution performance (ΨCA) at TCONTROL. Figure
These two points define the operational limits for the processor for DTS 1.1
implementation. At TCONTROL the fan speed must be programed such that the resulting ΨCAis better than or equivalent to the required ΨCA listed in Table
speed should be set at DTS =
TCONTROL to DTS =
Thermal/Mechanical Specifications and Design Guidelines | 71 |