[time-nuts] Linear voltage regulator hints...

xaos xaos at darksmile.net
Thu Dec 11 19:37:22 EST 2014


I don't know if this is the right time to ask this but here goes.
I have started a design for a linear power supply for the Beagleboard

5V 5-10A. Over-Voltage, short circuit and temp protection.
Very low ripple and HF noise.

I have been watching this thread and I am still not sure
what device would give me what I want. I am not as good as
some circuit designers here, to design a PS
via discreet transistors. Dr. Bruce Griffiths comes to mind.
He would probably do this with his eyes closed.

So, I need to use a regulator chip.

The TI TPS7A4700 looks great but it can only supply 1A.

Any other candidates ?

I am sorry if I am somehow asking an obvious question.

-George

On 12/11/2014 06:26 PM, Neil Schroeder wrote:
> So I've done a lot of work in power lately and I can summarize some of this
> quickly:
>
> The lowest noise LDOs today are the TI TPSa4700/01 up to 36v/1a and about 4
> uVRms noise,  and the ADP7154/55 up to 5.5v and 600ma with only *0.9* uVRms
> above 100hz.
>
> Both feature great PSRR -and in the case of the ADI part don't even
> recommend filter caps at all.
>
> The TI however does still recommend some capacitance.
>
> Now most people's next question  is how to get their ruby or their
> septuple-oven homebrew design powered by one. The quick answer is an error
> amplifier based ldo balancer for the most accurate distribution of current.
> Also helps with heat.
>
> Will share a sketch when at my desk next.
>
>
> On Thursday, December 11, 2014, Hal Murray <hmurray at megapathdsl.net> wrote:
>
>> eb at telight.com <javascript:;> said:
>>> If the plan is to use a three-terminal regulator after all, I'd  suggest
>> not
>>> using a low-dropout (LDO) type if the raw input supply is  noisy - the
>> LDOs
>>> usually have PNP output transistors (for positive  regulators), so may
>> tend
>>> to have poorer HF input ripple rejection  than equivalent ones with NPN
>>> passers.
>> In this context, what is "high"?
>>
>> Why don't filter caps solve that end of the spectrum?
>>
>>
>> --
>> These are my opinions.  I hate spam.
>>
>>
>>
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