Multiplex your inductor [Design]

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From: Winfield Hill on 30 Mar 2010 18:54

I missed this when it first came out in 2004 - TI
introduced a four-output SMPS chip meant for cell
phones, very small, and to even further save size,
it required only one small inductor. The secret?
Multiplex your precious inductor cycle-by-cycle,
among three outputs! Create +5, +20 and -18, all
from one 10uH inductor. It's TI's tps65120 to 24.

http://focus.ti.com/docs/prod/folders/print/tps65120.html

Stay happy.

--
Thanks,
- Win

From: Jim Thompson on 30 Mar 2010 19:43

On 30 Mar 2010 15:54:29 -0700, Winfield Hill
<Winfield_member(a)newsguy.com> wrote:

> I missed this when it first came out in 2004 - TI
> introduced a four-output SMPS chip meant for cell
> phones, very small, and to even further save size,
> it required only one small inductor. The secret?
> Multiplex your precious inductor cycle-by-cycle,
> among three outputs! Create +5, +20 and -18, all
> from one 10uH inductor. It's TI's tps65120 to 24.
>
> http://focus.ti.com/docs/prod/folders/print/tps65120.html
>
> Stay happy.

Clever! Thanks for the lead, Win!

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

The only thing bipartisan in this country is hypocrisy

From: miso on 30 Mar 2010 22:24

On Mar 30, 3:54 pm, Winfield Hill <Winfield_mem...(a)newsguy.com>
wrote:
> I missed this when it first came out in 2004 - TI
> introduced a four-output SMPS chip meant for cell
> phones, very small, and to even further save size,
> it required only one small inductor. The secret?
> Multiplex your precious inductor cycle-by-cycle,
> among three outputs! Create +5, +20 and -18, all
> from one 10uH inductor. It's TI's tps65120 to 24.
>
> http://focus.ti.com/docs/prod/folders/print/tps65120.html
>
> Stay happy.
>
> --
> Thanks,
> - Win

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1051
MAX212, done in 1994. I'm sure someone beat me to it since the idea is
pretty simple. You are limited to discontinuous conduction converters.
The 212 is clockless (self timed) so that the inductor value isn't
critical. Also a very high PSRR internal reference to avoid a
reference bypass cap. You had to make these parts very simple for the
232 crowd. In the day when you had serial mice, you wish you had these
chip on your notebook mobo.

From: Joerg on 31 Mar 2010 17:19

miso(a)sushi.com wrote:
> On Mar 30, 3:54 pm, Winfield Hill <Winfield_mem...(a)newsguy.com>
> wrote:
>> I missed this when it first came out in 2004 - TI
>> introduced a four-output SMPS chip meant for cell
>> phones, very small, and to even further save size,
>> it required only one small inductor. The secret?
>> Multiplex your precious inductor cycle-by-cycle,
>> among three outputs! Create +5, +20 and -18, all
>> from one 10uH inductor. It's TI's tps65120 to 24.
>>
>> http://focus.ti.com/docs/prod/folders/print/tps65120.html
>>
>> Stay happy.
>>
>> --
>> Thanks,
>> - Win
>
> http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1051
> MAX212, done in 1994. I'm sure someone beat me to it since the idea is
> pretty simple. You are limited to discontinuous conduction converters.
> The 212 is clockless (self timed) so that the inductor value isn't
> critical. Also a very high PSRR internal reference to avoid a
> reference bypass cap. You had to make these parts very simple for the
> 232 crowd. In the day when you had serial mice, you wish you had these
> chip on your notebook mobo.

And as usual nearly unobtanium, a whopping 58 pieces left to be scraped
off the bottom of the barrel:

http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=MAX212

It's sad, they employ smart engineers like yourself and then seem to
waste so much of their creativeness by screwing up the logistics.

This is how it's done right:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=296-17184-1-ND

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

From: legg on 31 Mar 2010 23:07

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