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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