Power Products FAQ
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Power Products FAQ
What is the VITA 62 Standard?
VITA 62 defines both the mechanical and electrical requirements for COTS modules intended for the creation of modular power supplies that are compatible with VPX specifications. VITA 62 also defines the power generation requirements for the modules and 3U and 6U backplane slots that can be used for these power systems.
VITA 62 supports Single-Stage and Two-Stage power subsystem configurations.
Single-Stage is where modules receive the prime power as the input and generate the outputs required by this standard. This can be accomplished by a single unit or by multiple units in parallel depending on the overall power requirements. Two-Stage is where the modules which generate the final regulated outputs (Final Power) receive their input from Front-End Modules via an intermediate voltage
There are four types of standard modules defined by VITA 62 Single-Stage Modules: Take in the prime power and provide the outputs required by this standard Front-End Modules: Part of a two-stage system, whereby the Front-End unit takes in the prime power and converts it to an intermediate voltage Back-End Modules: Also part of a two-stage system which accepts an intermediate voltage and provides the outputs required by this standard Energy-Storage Modules: Provide Holdup time and can be either powered by the prime power or with intermediate power as a backend unit
NAI offers solutions for each of these module types
In VITA 62 (VPX) power supplies, what is the VBAT signal and how would I use it? The VBAT option is part of the VITA62 power supply specification. This specification states that the power supply may either be the source of the VBAT signal or an energy storage module (such as a battery) can be used in the power supply. NAI chose to use the power supply +3.3_Aux output to provide the VBAT and not the battery. The VBAT output is intended for powering low power devices (up to 1Amp) such as a clock or a processor in sleep mode, etc. The reason one would use the VBAT output vs. the +3.3V_Aux output is because this provides a separate line to dedicate to low power needs and it has its own, separate overcurrent protection. It would not be affected by any type of overcurrent situation that may occur on the +3.3_Aux output. The intention of this output is not to connect to a battery as it would apply a lot of leakage current onto the battery and quickly discharge it. In addition, The VBAT has a re-settable fuse which if triggered will reset when load is removed.
What is the ENABLE* / INHIBIT* feature on VITA 62 power supplies and how is it used?
ENABLE* and INHIBIT* are Control Inputs used to change the output status of the power supply. Dependent upon the status of these two controls the outputs can be configured:
1) To all be on 2) To all be off 3) To have just the +3.3V_Aux on with the others off
Additional information can be found in the Power Applications Notes section: Application Note, Using ENABLE* / INHIBIT* on VPX Power Supply. Link to this section is below:
ApplicationNotes (naii.com)
What is the FAIL* Signal and what will cause it to trigger on NAI VITA 62 power Supplies?
FAIL* is part of VITA 62 and the intent of it is to indicate to other modules within the system that the VITA 62 power supply is enabled and that the outputs are within specification. Any condition which causes the outputs to not be within spec will cause the FAIL* to trigger. This can include an Overvoltage or an Overtemperature condition.
What is the Current Share Feature and how do I implement it?
Current Share allows the user to connect two or more power supplies in parallel to either increase system power or provide redundancy. For units with the current share feature, there is one pin named “share” for each output that has this available. To implement the current share feature, you simply connect each of the share pins for each individual output via the system wire harness or backplane. Best practices should always be employed to minimize noise on the share pins and sense lines. To best achieve sharing, all share lines should be connected and remote sense lines need to be connected to the load. The remote sense lines from multiple power supplies should be terminated to the same single point of the load, when possible.
NAI designs utilize a proprietary algorithm to provide sharing. The algorithm uses bi-directional communication through the pins designated as “share” on the interface connector. The units will negotiate to determine a master; the remaining units will act as slaves. The master will vary the output voltage of the slaves to achieve sharing.
What is the purpose of Remote Sense and how do I use it?
Remote sense is a feature which compensates up to a 0.5 VDC drop caused by the output leads. It is used by simply connecting the +Sense and –Sense signal(s) directly to the same signals that the output wires connect to at the load(s). If not using the remote sense, it is recommended that the sense lines be terminated as close to the output connector as possible.
What is component derating and how does it benefit the product?
Component derating is the practice of applying (designing in) components at lower than their maximum ratings (e.g. voltage, current and temperature). This enables the power supply to work throughout its full temperature range at full load, as well as extending a longer operating life. You do not have to “over buy” the power supply. All NAI power supplies are designed to the component derating guidelines of NAVMAT/NAVSO P-3641A.
If I choose not to use Remote Sense, how do I connect the unit and what results should I expect?
If you are not using this feature, it is recommended that the sense lines be terminated as close to the output connector as possible. When this feature is not in use, you can expect the output voltage to be up to 0.5 VDC higher than the rated output.
How do I cool NAI power supplies?
All NAI power supplies are conduction cooled through either a baseplate or wedgelock/edge.
On baseplate cooled versions, the power supply should be mounted to a metal surface (preferably aluminum) via the mounting screws shown on the specification outline diagram. This metal surface needs to be as flat as possible. It is also recommended that a thermal pad be used to assist with the thermal transfer. On the wedgelock cooled versions, install the power supply into the card slot and ensure that the wedgelocks are tightened, making good contact with the card guides. It is also important to note that for both versions the specified power supply operating temperature and loads are not exceeded. How do I use the Remote Turn On/Off feature? This is a TTL level signal which uses two lines (+TTL and –TTL). Leaving these two lines disconnected (floating) or connecting them to logic 0 keeps the power supply output(s) enabled at all times. Connecting these two pins to logic 1 will disable the power supply output(s). It should be noted that in order to apply this logic 1, a +5 VDC source will be needed.
What if I am not able to find exactly what I am looking for in your standard product offerings?
NAI specializes in providing a wide variety of Modified COTS and Custom Power Supplies – including configurations that meet VME, cPCI and VPX (VITA 62) requirements - to meet the exact needs of our customers. Visit our Modified COTS Power Supplies page for more details on our design approach and Configurable Open Systems Architecture that allows customers to select from a full-feature library to create high reliability power solutions that meet their specs – with little or no NRE.
What type of acceptance testing is performed on NAI power supplies?
All NAI power supplies are 100% performance tested on ATE’s. Test data is stored for each unit and is available upon request. In addition to performance testing, the following tests are performed:
Temperature Cycle testing is performed per NAVMAT guidelines on all of our products. This test is typically run for twelve cycles. Units are placed under full load and are cycled to the cold and hot temperature extremes, powered up at each extreme, monitored and data logged.
Random Vibration is performed using a NAVMAT profile at 6 G’s, one axis which is normal to the mounting plane. Vibration on our standard products is performed on an AQL basis, or for an associated fee on a 100% basis. Do you provide mating connectors with your power supplies? No, we do not provide mating connectors, however power supply specifications provide generic part numbers for mating connectors. NAI typically specifies connectors which are readily available through most parts distributors.
What is your general product obsolescence policy?
North Atlantic Industries generally continues to offer products as long as there is customer demand and we can continue to procure the materials to manufacture them. If it becomes necessary to discontinue an item, NAI will notify all of its customers of a lifetime buy, or we will offer a form, fit & function product replacement. Discontinued products are typically supported for two to three years.