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Low current logic to RS232 conversion

Hi, I need to generate an RS232 signal from a TTL line. + & - 12v supplies available, and the setup must be low current draw. Currently I'm using 8 pin DIP SN75155s, neet footprint but the quiescent current drain is over 8mA which is too high here. 1488s are even higher. The alternative seems to be to use discretes, but with my limited design skills I keep ending up with what seems to be a ridiculously high component count - 4+ semis and 6+ resistors by the time I've managed to drive from both rails. Surely there's a neat way of doing this that also keeps the current draw right down (ideally < 1mA on either supply with no imposed load). Anyone have a suggestion? TIA

Reply to
Bruce Varley
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On Tue, 19 Aug 2008 19:48:29 +0800, "Bruce Varley" put finger to keyboard and composed:

Here is a design for an RS232-to-5V interface cable between a Casio diary and a standard RS232 device:

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The design is powered from the RS232 interface pins, so I assume the current draw is low. The author states that several components can be omitted, so you can probably get away with a single FET, zener, and four resistors.

Otherwise have a look at Maxim's line of RS232 chips.

- Franc Zabkar

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Reply to
Franc Zabkar

Bruce, have a look at:

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looks like 5V@.5ma

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Max3238e, check it out and make sure I didn't read it wrong.

Cheers Don...

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Don McKenzie

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Reply to
Don McKenzie

The MAX3222 comes to mind, takes around 0.3mA supply current. No need for the +/-12V rails, generates it's own (double the supply voltage, you don't actually need 12V). Maxim probably have even lower power devices than that too.

Dave.

Reply to
David L. Jones

I know I'm stating the obvious but have you tried using a humble opamp?

*Peter*

Bruce Varley wrote:

Reply to
Peter Jakacki

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