Lpc2000

You'reWelcome. When I last did this digital pots were $2-3. I'd look at 
the 573 rather than the 373, it is bussed nicely, 8 inputs on one side, 
8 outputs on the other. I use this all the time, especially the 
SN74LVTH573 in SSOP, about $0.24. It is much cleaner to interface than 
the 373, and this version is 3V3 operating 5V tolerant. The Mc14051 was 
used  in one design becasue I had 1000's of them that needed a good 
home, and it worked well, saving me precious I/O. All of these are good, 
fairly clean solutions, and cheap.

Cheers

Al

Sean wrote:

>I am liking the MC34063 idea, it's only $0.50 in 100qty, plus $0.85 for 
>supporting components.  Add in a digital pot (i.e. MCP4021 - $0.70) in 
>place of the R1 for the comparator circuit (which controls the voltage) and 
>you can get a digitally adjustable contrast regulator (64 steps) for about 
>$2.  In place of the digital pot you could always use an 8-bit latch (i.e. 
>74HC373) with a variety of resistors, that would only be about $0.50 and 
>give max 256 levels of control.  In either case, those look like pretty 
>good solutions.
>
>Thanks for your input!
>
>-- Sean
>
>At 04:49 PM 1/13/2006, you wrote:
>  
>
>>After messing with this one for years I finally went to Winstar and get
>>mine on baord for free, however prior to that for digital control I used
>>the MAX686, not a cheapest solution but solid, and not too expensive.
>>The other cheap way might be to use an MC34063, they are only $1, but no
>>digital control, or ON/OFF control without a bit of messing. I used an
>>MC14051 ($0.38) and a variety of resistors to get numerous voltage steps.
>>
>>Cheers
>>
>>Al
>>
>>Sean wrote:
>>
>>    
>>
>>>Sorry for the OT post, but I figure that since this is something common to
>>>embedded projects you guys might have an elegant solution.
>>>
>>>I'm looking to create a contrast voltage (typ -13V 10mA) and a LCD Drive
>>>voltage (min -23V 10mA), onboard I have +5V, +3.3V and Vin which is
>>>typically +12V.  Ideally the contrast should be digitally controllable.
>>>
>>>The big part of the problem: it needs to be relatively cheap.
>>>
>>>I've been having a hard time trying to figure out the best way to do
>>>this.  The best way that I can think of so far is going to be via voltage
>>>multipliers.  I.e. take 3.3, invert and quadruple to get -13.2V for the
>>>contrast, and then double again to get -26.4V for the LCD Drive.  I don't
>>>know however if I can handle 10mA this way after octupling the voltage.
>>>
>>>I'm trying to stay away from switched regulators, as they can get expensive.
>>>
>>>Thanks for any suggestions that you may have.
>>>
>>>-- Sean
>>>
>>>
>>>
>>>
>>>Yahoo! Groups Links
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>      
>>>
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