Paulo,

 True, but it cannot withstand the 80 Volts in for any appeciable
 time.

                                           Regards,

                                             Jim

On Thu, 16 August 2001, Paulo Ricardo Pabst wrote:

>
> Hi,
>
> Another good idea is the MC78L05ACP from Motorola.
> It a small +5Vdc regulator in a TO-92 package and can
> source 100mA.
>
>
> ------------------------------------------------
> Paulo Ricardo Pabst.
> R&D
> Pollux - Industrial Machine Vision and Tracking.
> Joinville - SC - Brazil
> ------------------------------------------------
>
> |-----Mensagem original-----
> |De: pic microcontroller discussion list
> |[mailto:PICLIST@MITVMA.MIT.EDU]Em nome de Lyle Killough
> |Enviada em: quinta-feira, 16 de agosto de 2001 14:06
> |Para: PICLIST@MITVMA.MIT.EDU
> |Assunto: [EE]: tiny power supply
> |
> |
> |I have a power supply problem which I am hoping to get some good
> |suggestions
> |on..... (I have lots of my own bad ideas)
> |
> |I am designing a small PIC-based device for use in mobile hydraulic
> |machinery.  There is VERY little room on the board - the
> |board will be less than .85x.75 inches / 22x19 mm, and there will be a 3A
> |high-side (solenoid) driver along with a PIC12CE673 and a linear
> |Hall effect
> |sensor in a TO-92ish package.  The board will be potted into a .25" / 6mm
> |thick package.
> |
> |The device will be connected to anything from 10 to 26 VDC with a power
> |supply requirement of 20 mA @ 5 VDC.  All of the hideous automotive-type
> |abuse will be present; e.g. reversed battery, load dump, battery disconnect
> |and voltage peaks.  In addition, one of our customers has specified a 2
> |minute, 80 volt survival test.
> |
> |The obvious solution of a LM2931-5.0 with a 32V over-voltage shut-down will
> |not work.  Way too much heat for a little linear regulator.
> |
> |I have a working option which will allow 10 to 80+ volts in, 5 volts out
> |with about .25 volts of ripple.  This is really just a voltage comparator
> |maintaining a voltage on a capacitor with a Schottky diode in the
> |hysteresis
> |loop.  This is built with discrete transistors to allow the large supply
> |voltage range.
> |
> |I know very close to nothing about switching power supplies, but I suspect
> |that there is a buck regulator which will do this in a neat
> |package.  I have
> |looked in the obvious places, but I cannot find a device which
> |will take the
> |high input voltages in a small (low pin count) package.  I prefer to not
> |have an inductor in this supply, current demand is low, I wish to minimize
> |stray magnetic fields due to the Hall effect sensor, and there is so little
> |space.
> |
> |If any of you PICsters have any suggestions or cautions about how
> |to achieve
> |the above, I'd love to hear about them.
> |
> |Thanks!
> |
> |
> |____________________________________________
> |
> |Lyle Killough      lyle@suregripcontrols.com
> |____________________________________________
> |
> |           Sure Grip Controls Inc.
> |             4 - 1413 McGill Road
> |            Kamloops, BC, V2C 6K7
> |                   Canada
> |
> |              phone 250-374-2278
> |              fax   250-374-1099
> |
> |____________________________________________
> |
> |          www.suregripcontrols.com
> |____________________________________________
> |
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> |
> |
>
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jim@jpes.com

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