Intel NetStructure ZT 5085, Руководство пользователя

Страница: 93 / 106

93
Technical Product Specification
Power Supplies/Hot Swap Circuitry
Power Supplies/Hot Swap Circuitry B
Intel
®
NetStructure™ hot swap products are essentially electrically isolated from the midplane
when installed or removed. This prevents transients from corrupting midplane communication
when a product is installed or removed while the system is operating.
When boards are installed or are powering up, the board's hot swap circuitry monitors the power
supply voltages available. Until the proper voltages are present, the board does not power up. This
creates a concern when using power supplies that require a minimum load to start up. The
following topics address this issue.
B.1 The Power Supply Perspective
Power supplies typically have two minimum load requirements for the primary output to operate
properly:
•
The minimum start-up load requirement (typically 100-200 mA).
•
The minimum regulation load requirement. This requirement must be met to guarantee that the
power supply’s auxiliary outputs regulate properly when fully loaded, even if the primary
output is not fully loaded. This is typically specified as 10% of the maximum output capability
of the primary output.
In a pure hot swap system, the power supply essentially sees no load even after the input power to
the system is applied because the hot swap circuitry remains disabled until the voltage levels reach
the appropriate value. The power supply never generates the proper voltage until it sees a load.
They both wait for each other and the system never powers up.
When configuring a pure hot swap system, minimum start up loads for the power supply must be
considered. This can be accomplished in a number of ways. The most direct solution is to include a
simple power resistor in the system to provide the start up load necessary for the supply.
B.2 Intel
®
NetStructure™ Power Supplies
The Intel
®
NetStructure™ power supplies that Intel currently provides do not require a minimum
start up load. Additionally, the current Intel NetStructure power supplies do not have any regulation
load requirements except that the +12 V load must be at least 50% of the -12 V load. The fan trays
used ZT 5085 assure that the minimum regulation load is met.