[SI-LIST] Re: Xilinx SpartanT-3/3E/3L FPGA Power Solutions-- FromMonolithic Solutions
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Bharathi <bharathi@xxxxxxxxxxxx>
- Date: Thu, 05 Mar 2009 03:45:13 -0800
How much efficiency you maintain over a wide range depends on how much
cost and real-estate you are willing to give up. In order to improve
efficiency at the high current end you need to use more copper in your
magnetics, and lower loss semiconductors in your switch stage. Lower
resistance MOSFETs have more gate charge that you will see as loss at
all loads. If you are trying to handle a wide range of input voltages,
you will need larger magnetics than if you restrict the voltage range.
Steve
Bharathi wrote:
> Vivek,
>
> The efficient is not the same across varying loads. Only at some loads, the
> efficient is very high. To achieve the efficiency need to have low ESR
> capacitors on the input and output. If you are interfacing this buck to the
> FPGA, I would look in the power supply sensitivity of the FPGA. The reason
> is the ripples on the buck output. The ripple amplitude depends on the
> components and layout.
> Hope this help
>
> Regards
> Bharathi
> Tessolve Services Pvt. Ltd
> 11/7, 10th Street, Dr VSI Estate
> Thiruvanmiyur
> Chennai 600041
> Tel: +91-44-43357111
> bharathi@xxxxxxxxxxxx
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Vivekkumar M-TLS,Chennai
> Sent: Wednesday, March 04, 2009 6:11 PM
> To: Istvan.Novak@xxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Xilinx SpartanT-3/3E/3L FPGA Power Solutions--
> FromMonolithic Solutions
>
> Dear Istvan Novak,
>
> Thank you for your inputs.
>
> If we design the Regulator for an entire range, will there be an effect
> on the efficiency?? Please advice us.
>
> Regards
> Vivek
>
> -----Original Message-----
> From: Istvan.Novak@xxxxxxx [mailto:Istvan.Novak@xxxxxxx]
> Sent: Wednesday, March 04, 2009 5:44 PM
> To: Vivekkumar M-TLS,Chennai
> Cc: si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Xilinx SpartanT-3/3E/3L FPGA Power Solutions--
> FromMonolithic Solutions
>
> Dear Vivek,
>
> You can approach the question from the opposite end as well. If you have
> a given design for a certain maximum current, you rightfully want to use
> that design with a load current anywhere between zero and full maximum
> allowed load. And of course, you dont want to change components on the
> fly just because the load current has changed. Your point is valid
> though:
> external components should be
> designed with the operational range in mind. If you design the circuit
> to work well in the entire range (in this case 0 to 3A) but use it only
> in a subrange (0 to 1A), the result will be somewhat suboptimum, but
> still may work very well.
>
> Regards,
>
> Istvan Novak
> SUN Microsystems
>
>
> Vivekkumar M-TLS,Chennai wrote:
>
>> Dear All ,
>>
>> I happened to look into the Step Down Converters from MonothilicPower.
>> The following is the statement made in the webpage:
>>
>> MPS presents the MP2309 and MP2307 23V synchronous step-down
>>
> regulators.
>
>> With an output current rating of 1A and 3A respectively, the MP2309
>> and
>> MP2307 are pin compatible with the 2A MP2305, forming a power
>> management solution that can easily scale from 1A to 3A without
>> circuit board re-design.
>>
>> http://www.monolithicpower.com/fpga_xilinx_spartan.htm
>>
>> Could anyone please explain how come this is feasible.
>>
>> Following are the general rules for a step Down converter:
>>
>> 1) Since the input capacitor (C1) absorbs the input switching current
>> it requires an adequate ripple current rating.
>> 2) The worst-case condition occurs at VIN = 2VOUT,where IC1 = ILOAD/2.
>> 3) Inductor should be chosen that it will not saturate under the
>> maximum inductor peak current. The peak inductor current hence is
>> dependent on the Load Current.
>>
>> Hence how is that if we want to change to a different load
>> requirement, only a Monolithic power solution Chip change is enough.
>> How come the external components remain with the same rating for
>> different loads.
>>
>> Please can anyone explain this . It will be of great learning to us
>> here.
>>
>> Thanks
>> Regards
>> Vivek.
>>
>>
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