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Q&A
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Hot-Swap Technology for Backplane

  • Q: Do we need to append any additional circuit when we use the NS's hot swap? How many components are required?
  • A: National's Hotswap devices are made with lot of versatality built in. The external components are used to make it more efficient at the same time many protections are implemented. You will need mainly a MOSFET, a current sense resistor, a timing capacitor
  • Q: What are the prices of these NS's hot swaps? Where we can buy the products?
  • A: You can refer the product page for 1Ku price. Sample is orderable from website. If you need more quantity, kindly contact local National office or our authorise distributor.
  • Q: We call it "a hot swap circuit is a switch". Does this switch generate in-rush current or inductive spike when it works?
  • A: Inductive spike may happen only when fault condition, or when the gate is suddenly shut off. This will caused large spike on the input line due to parasitic inductor. A snubber or transorb, or combination of both can help to overcome this issue.
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Understanding Fractional-N PLLs

  • Q: PLL utilization in Automotive
  • A: Automotive uses PLLs in many places.The best example is the GPS communication to generate the links with satellite. The other applications like the RF connectors (wireless) like MOST interface LANs uses the PLLs extensively. Apart from this, for superheterodyning in the IF stages of FM radios in automotives also PLLs are used. It is also used in Automotive cruise control radars to generate high frequencies for ranging.
  • Q: can you suggest further reading on Dithering
  • A: There is a very good book written by Mr Dean Banarjee from National Semiconductor. The name of the book is : "PLL Performance Simulation and Design" You can down load this book from National's website at :http://www.national.com/analog/timing/pll_designbook. Or you can buy from Amezon.com.
  • Q: Why can not we use fractional PLL everywhere ? Just power consumption is an issue ? Vinod [Auxineon, Bangalore]
  • A: As you know we use fractional N PLL because of its fine frequency step capability and lower synthesizer noise with a high PDF. But there is also limitation for N fractional PLL. AS Nfractional is directly related to the resolution of the fractional-N PLL, FDEN, which is depending on the number of bit of the N-counter.
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High Performance SIMPLE SWITCHERs - New Technology to Make Designs Easier

  • Q: What are engineers' design challenges in power management design?
  • A: The major design challenges in power management design are stability, EMI problem and limited time to push the product to market etc. It is relate to the following reasons. (1) Compensation network (2) Power sequencing (3) Frequency synchronization (4) PCB layout So, National's "SIMPLE SWITCHER" and WEBENCH design environment can helps make design easy.
  • Q: What is the advantage of the National's high-performance switching regulators?
  • A: Hi, The advantages of our Switching regulators are : 1. Wide vin range ( low as 4.5V and high as 75V, depending on your requirement ) 2. Both fixed frequency and adjustable frequency versions are available for more flexibility in design 3. Low component count ( because compensation is internal ) 4. Available in thin TO-263 package improving thermal performance and reducing overall system size. 5. Webench support available including thermal simulation
  • Q: What is the input voltage range of the NS's high-performance switching regulators? And what is the lowest output voltage?
  • A: Input voltage range of our switching regulators is high as 75V and 4.5V on lower side depending on your requirement. The lowest output voltage is 1.23V / 1.285V
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Automotive LED Lighting Solutions: Challenges and Solutions

  • Q: Dear Dilip£¬ With contineous operation LED life / light output drops drastically due to temperature effect. How it should be taken care in the design without adding any flicker or heat sink. Best Regards£¬ Ganesh Mohol
  • A: for power LEDs. :-best way is provide better Heatsink Metal core PCB + Thermal paste + heatsink to maintain junction temp within specified limits. Heat sink calculation tools are available Flow therm by Mentor graphics or Our channel partner Future electronics ( website www.futurelightingsolutions.com) has heat sink design tool called as QLED software .or can use National Semiconductor Webench tool. The another method is to use Temp sensor ( mount on Heat sink) to sense LEd temp . this feedback you can give to u controller . ucontroller will adjust DIM signal to reduce the LED current if LED temp is more than specified temp.
  • Q: I want to measure the intensity of a LED used in automotive application. I have a LuxX meter which will give interms of LUX. But I need interms of Candela. please provide me the conversion equatio
  • A: Susanto, You can use Spectrophotometer to measure Intensity in candela. you can download lux to candela conversion tools from www.google.com or you can use Photometric distance law or Inverse square law Ev = Iv / d*d where , Ev = Illuminance (lux) Iv = Luminous intensity ( Candela) d = Distance of lamp source from surface
  • Q: i want to boost 12vdc to 20-30vdc with current limit not more than .90amps
  • A: You can use LM5022 boost LED driver to boost 12V to 20/30V @ 1Amp or less for more details pls contact National Semiconductor Bangalore ofice email :- Dilip.Mohol@nsc.com
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Making Point-of-Load Power Supply Design Easier

  • Q: Welcome to National Semiconductor online seminar
  • A: Attendees who complete and return survey after the webinar will get a PowerWise polo shirt made of easy dry material to keep you cool.
  • Q: is it possible to implement on Mobile phonep product?
  • A: The products we presented today are for input voltages in the medium and high voltage range. These products finds applications in industrial, automotive and telecom segments. This is because almost all of these devices handle voltages in the range of 6V to 42V and some upto 75V. Where as in Mobile applications we use one Li-Ion battery as source and voltages lesser than 5V. But National has a big range of devices to cater to mobile handsets. You may refer to them at: http://www.national.com/analog/portable
  • Q: do you have anything which serves both buck and boost
  • A: Yes. National has devices for applications which require both buck and boost. LM5118 is one such device. You can access the datasheet, design tools and other application notes on this device at: http://www.national.com/pf/LM/LM5118.html
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Design Made Easy with National's Online Design Tool

  • Q: I need to design a signal conditioning unit for piezo electric accelerometer£¬ i.e. charge amplier£¬ ADC
  • A: May we know specification of your piezo electric accelerometer and operating condition of your system? thanks.
  • Q: my board fan dont¡°t work ?
  • A: can you explain more details? What is content of your board?
  • Q: Sensitivity and Stability is very important factor for designing sensor front-end circuit. How to evaluate the sensor design is optimized for sensitivity and stability.
  • A: good question ! 1.Sensitivity depend on your sensor and AMP. After senosr chose ,you should chos precision amp. to get high sensitivity . In your application you can change differnt amplifiers to meet you sensitivity in our sensor Webench. 2.Stability : B
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