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Carl's PI-1 question

A

Anonymous

Guest
Hi,
I took a look at the pi-1 project on Carl's site today. Correct me if I'm wrong but it looks to me like he is feeding it with 12Volts and I went to the data sheet on the ICL7660 to see what kind of current it will source and I noticed that its rated for a maximum of 10Volts. Am I missing something?
Thanks,
FJ
 
Hi FJ,
Looking at the Maxium part and at Carl's circuit it looks like you got it right. Several manufacturers made these things and pseudoclones so maybe one or more of those is good for it.
Surprised this was missed for so long, or is Maxium wrong? Interesting, never used the things myself.
JC
 
Hi FJ,
Well think Harris orginally made the part because of the ICL prefix and found one of their datasheets and it goes to 13 volts and then fries.
So morale of story is don't use no new fangled devices. Old stuff is always better.
JC
 
Hi JC,
Before I wrote the post, I looked at about 3 different data sheets, including Maxim's, and they all went to 10 volts. Maybe the "S" suffix is the difference. I'm surprised no one has had a problem yet.
Thanks,
FJ
 
Hi FJ,
I never messed with any of these things but this part isn't so close to the battery voltage, charged up to 12+ volts on lead acid. Guess it will do the same job but haven't really checked, it out. Someone here must know about these beasties.
JC
 
I used the 7662 in a design some years back. It does the same job as a 7660, but can take up to 20V input voltage.
Eric.
 
Hmmm... good point. The data sheet I've been using is for the Intersil (formerly Harris) ICL7660S, which is 13v. But I see that there is also a 7660, and a 7660A, both rated for 10v.
To add more confusion, the parts I got from Digi-Key are "AS7660P" from Alpha Semiconductor. I can find no info at all on these, even the company doesn't seem to exist any longer.
So, I s'pose that I am most likely running the chip over its stated limit. I suspect that, for the process used for these chips, the breakdown voltages are high enough that they will safely run at 12v. Haven't heard of any failures with this chip on the PI project... yet.
- Carl
 
Carl,
How about sticking a few diodes in series with the 7660's input to drop the voltage?
 
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