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From: Joe G (Home) on 1 May 2010 23:36
Hi All,

My radio device requires the following Vin Specifications

Vin range 3v2 to 4v5 nominal 3v6
Current 2amps peak
Ripple less than 250mV up to 10KHz,
Ripple less than 40mV from 10kHz to 100kHz and
Ripple less than 5mW greater than 100KHz

From the outside world I would like to supply my radio devices with a
voltage range 9 - 36V

What can you suggest for regulator options?

Should a use a two step approach.... a pre-regulator to drop the voltage
down to 9-12V then a very low ripple DC-D regulator.

Should I add DC capacitive filtering to achieve the ver low ripple
requirements


What can you suggest?


Thanks in advance.

Joe


From: Phil Allison on 2 May 2010 01:35

"Joe G (Home)"
>
> From the outside world I would like to supply my radio devices with a
> voltage range 9 - 36V


** More details needed.

What is the supply of voltage ?

An old car battery charger ??

Solar cells ??

Bicycle dynamo feeding a bridge ??



..... Phil




From: Jim Thompson on 2 May 2010 11:20
On Sun, 2 May 2010 13:36:11 +1000, "Joe G \(Home\)"
<joe.g(a)optusnet.com.au> wrote:

>Hi All,
>
>My radio device requires the following Vin Specifications
>
>Vin range 3v2 to 4v5 nominal 3v6
>Current 2amps peak
>Ripple less than 250mV up to 10KHz,
>Ripple less than 40mV from 10kHz to 100kHz and
>Ripple less than 5mW greater than 100KHz
>
>From the outside world I would like to supply my radio devices with a
>voltage range 9 - 36V
>
>What can you suggest for regulator options?
>
>Should a use a two step approach.... a pre-regulator to drop the voltage
>down to 9-12V then a very low ripple DC-D regulator.
>
>Should I add DC capacitive filtering to achieve the ver low ripple
>requirements
>
>
>What can you suggest?
>
>
>Thanks in advance.
>
>Joe
>

Google on "buck regulator".

...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: MooseFET on 2 May 2010 12:32
On May 1, 8:36 pm, "Joe G \(Home\)" <jo...(a)optusnet.com.au> wrote:
> Hi  All,
>
> My radio device requires the following Vin Specifications
>
> Vin range  3v2 to 4v5    nominal  3v6
> Current  2amps peak
> Ripple less than 250mV up to 10KHz,
> Ripple less than 40mV from 10kHz to 100kHz and
> Ripple less than 5mW greater than 100KHz

Assuming no ripple on the input and a switcher running at
100KHz, the ripple values below 100KHz are all easily met.

The best design is likely to be a fairly simple bucker.

To get the low ripple, you need to be careful with where the
ripple currents end up flowing.


L1 ---------- L2 L3
IN-+--))))---+---! Switcher !---+---))))--+--))))--+--
! ! ---------- ! ! !
===C1 ===C2 ! ---D1 ===C3 ===C4
! ! ! ^ ! !
! ! ! ! ! !
! ---------+---+---- ! !
! ! GND1 ! !
! --------------+ !
! GND2 ! !
---+--------------------------------------+--------+----

You need to bring the ground end of C2 and D1 together directly
Move the parts around until they almost touch

The next priority is to get C3 to ground near the same point.

If this is a multilayer PCB, a GND1 can be an internal layer that
on other parts of the PCB is a trace layer. The whole idea here is
to keep the ripple currents local to the circuit.

If this is a stand alone item, the GND2, input and output should
all be in one small area. Don't put them on opposite ends of the
PCB as would seem intuitive.

The connection between C1 and C4 should be also as short as you can
make it.

L1 and L3 are basically large RF beads. They need to be lossy.


All the capacitors are actually collections of capacitors as
needed to get the ESR and ESL numbers low enough.

>
> From the outside world I would like to supply my radio devices with a
> voltage range 9 - 36V
>
> What can you suggest for regulator options?
>
> Should a use a two step approach.... a pre-regulator to drop the voltage
> down to 9-12V then a very low ripple DC-D regulator.
>
> Should I add DC capacitive filtering to achieve the ver low ripple
> requirements
>
> What can you suggest?
>
> Thanks in advance.
>
> Joe

From: whit3rd on 2 May 2010 15:13
On May 1, 8:36 pm, "Joe G \(Home\)" <jo...(a)optusnet.com.au> wrote:

> My radio device requires the following Vin Specifications
>
> Vin range  3v2 to 4v5    nominal  3v6
> Current  2amps peak
> Ripple less than 250mV up to 10KHz,
> Ripple less than 40mV from 10kHz to 100kHz and
> Ripple less than 5mW greater than 100KHz
>
> From the outside world I would like to supply my radio devices with a
> voltage range 9 - 36V

So, use a prebuilt DC/DC converter with regulation. For 24V input
and 3.3V output, these are easily available prebuilt and off-the-
shelf.
(input "24V" can mean a range of 9V to 36V...).

It's not usually worthwhile designing your own power converters; the
Murata/Power-One/Vicor/Ericsson... designs pretty much cover this
territory.

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