Voltage Regulator Module (VRM) and Enterprise Voltage Regulator-Down (EVRD) 10.2 Design Guidelines

Voltage Regulator Module (VRM) and Enterprise Voltage 33
Regulator-Down (EVRD) 10.2 Design Guidelines
8 VRM – Environmental Conditions
The VRM design, including materials, should be consistent with the manufacture of units that meet
the environmental requirements specified below;
8.1 Operating Temperature - PROPOSED
The VRM shall meet all electrical requirements when operated at Thermal Design Current
(Icc (TDC)) over an ambient temperature range of 0º C to +45º C with a minimum airflow of
400 LFM. The volumetric airflow (Q) can be measured through a wind tunnel. The VRM should be
mounted on a PCB, which is then mounted in a duct. The recommended duct cross section,
assuming the PCG is horizontal and flush with the bottom of the duct is as follows:
• Y direction duct width (perpendicular to flow, horizontal) = 0.3 m
• Z direction duct height (perpendicular to flow, vertical) = 0.15 m
• Minimum X direction duct length in front of VRM = 6 hydraulic diameters = 1.2 m
• Minimum X direction duct length behind VRM = 2 hydraulic diameters = 0.4 m
Velocity (v) is calculated from the volumetric flow and cross-sectional area at the inlet as:
• v = Q/(0.3 x 0.15)m
2
Operating conditions shall be considered to include 10 cycles between min and max temperature as
a rate of 10º C / hour and a dwell time of 30 minutes at extremes. Temperature and airflow
measurements should be made in close proximity to the VRM.
8.2 Non-Operating Temperature - PROPOSED
The VRM shall not be damaged when exposed to temperatures between –40º C and +70º C. These
shall be considered to include 50 cycles of minimum to maximum temperatures at 20ºC / hour with
a dwell time of 20 minutes at the extremes.
8.3 Humidity - PROPOSED
85% relative – operating
95% relative – non-operating
8.4 Altitude - PROPOSED
3.05 km [10k feet] – operating
15.24 km [50k feet] – non-operating