max232 Heating like hell!

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#1
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I have started using smt components oflate. I am having a problem with my max232 ICs. They seem to over heat up nearly like a short circuit condition.

I feel the unused port is creating a problem and causing the charge pumps to overheat. Any idea what do i do to the unused inputs(pull down to GND or pull up to Vcc)

Never had this problem with the normal DIP ICs

Thanks Rodney

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Unused inputs are pulled high by internal resistors, IIRC. You've connected them wrong if they are getting hot.

Leon

Leon Heller G1HSM

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If you are using polarized caps in the charge pump, make sure they care installed correctly. Check your + and - voltages on the chip. You should have approx +10V on pin2 and approx -10V on pin6 if you run it from 5V.

Check, also, that no RS232 transmit pin (pin 7 & 14) is shorted to ground.

I have never had problems leaving the unused channel un-terminated on either the logic side or the RS232 side.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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using non polorised chip capacitors. I have changed the ic and using a max3232 which is pin compatible. had to change the caps to 100nf too. seems fine for now.

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Are you sure there is no short circuit in your pcb design?

Michael.

User of:
IAR Embedded Workbench C/C++ Compiler
Altium Designer

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There are no shorts. was getting this problem on a couple of circuits. after changing to max3232 no problems.

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The current version of the MAX232E data sheet states: "Transmitter input pull-up resistors, enable, and shutdown are not provided on the ... and MAX232E." on Figure 3.
http://datasheets.maxim-ic.com/e...

I once failed to communicate with a MAX232ECPE. Problem was fixed when I connected the unused inputs simply in parallel with the used inputs. I guess the unused inputs were oscillating and brought the charge pump down.

I don't remember the chip heating, but then again I probably didn't touch it much.

- Simo

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I m using MAX3232(SMD)with ATMEGA32. It gets heated very much (untouchable). I have not been able to find out the reason.
CAN sending too much data heat the MAX3232?

PLease can anyone help me???

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sushil909 wrote:
CAN sending too much data heat the MAX3232?
I very much doubt it ... check the polarity and connections of your charge caps.

Ross McKenzie ValuSoft Melbourne Australia