[SI-LIST] Re: Xilinx SpartanT-3/3E/3L FPGA Power Solutions-- From Monolithic Solutions
- From: istvan Novak <Istvan.Novak@xxxxxxx>
- To: "Vivekkumar M-TLS,Chennai" <Vivekkumarm@xxxxxx>
- Date: Wed, 04 Mar 2009 07:13:55 -0500
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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