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I need DC-DC voltage converter circuits that converts 2.8V DC to 5V DC and no need extra power supply to operate circuit. It is better prescribe me elements which are easily found in the market. Your support in this regard will be highly appreciated.
Actually, what i want to do is, i have a 2.8V DC source, then after converting the 2.8V to 5V, the 5V output is connected to the MAX232 as VCC. On the other hand, can we give the 2.8V directly to MAX232 Vcc. While reading data sheet of MAX232, the Vcc ranges from -0.3V to 6V in absolute conditon.Is it possible. Please suggest me.
Hi, I work for Maxim. One of our support techs saw this thread and asked me to post a reply:
From your post earlier today, I believe that you may have misunderstood some of the information shown in the MAX232 datasheet. The Absolute Maximum Ratings, to which you have referred, are voltage limits for safe operation only and are not recommended operating conditions. Exceeding the voltages shown in the Absolute Maximum Ratings section of the datasheet may damage the part. That said, the operating voltage supply range for the MAX232 is not -0.3V to +6V: the MAX232 has been tested with an operating supply voltage of 5V only. If you try to operate the part with a different supply voltage, the part may not operate as expected.
Another person recommended using the MAX3232 instead of the MAX232. The operating supply range for the MAX3232 is listed as +3.0V to +5.5V in the datasheet, which is still slightly higher than the 2.8V available from your DC source. As before, operating the part with a supply voltage less than the limit shown in the Electrical Characteristics section of the datasheet may result in unreliable operation.
Depending on your other specifications, you might consider using the MAX3380E instead. The MAX3380E features an operating supply voltage from +2.35V to +5V, making it a viable option for your 2.8V DC source.
Please note that the receiver output of all of these devices is limited by the supply (or logic) voltage. A lower supply voltage will result in a lower output high voltage at the receiver output.
There are many 'single/double cell boost converters' out there. Most will happily operate from voltages as low as 1.2V start up (1.2-5v generally) and output 5v at a half decent current.
The advantage of using these IC's is efficiency (80-90%) and ease of use. I am not prepared to list all the ones I have tried. Make your own list, by going to manufacturers websites (maxim, TI, stmicro, national semiconductor, zetex, sipex...to name a but a few..)
I have recently purchased a lot of NCP1400A's, although these have a maximum output of 100mA, it is more than enough for a max232. There are of course many alternatives, so you're better off narrowing the search based on availablity. I can recommend zetex, spiex and national semi converters, as they all have a wonderful range of low current, ultra high efficiency single cell boost converters, which are cheap and easy to use...requires an inductor, and a couple of capacitors. At 2.8V, it could prove difficult to perform the task in question without a relatively complicated circuit, or hand winding components.
i remember seeing a boost converter with a starting voltage of 1.5 and a regulated output of either 5V or 12V (it was adjustable or settable with a zener). try doing a search at **broken link removed** in their "Design Ideas" section for "low voltage boost converters"... i'm sure you'll find plenty of them to work with. most of them you'll find there use discrete components, so getting parts won't be a problem.