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
Low current logic to RS232 conversion
Aug 19, 2008
4 Replies
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:
formatting link
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
Please remove one \'i\' from my address when replying by email.
Bruce, have a look at:
formatting link
looks like 5V@.5ma
formatting link
Max3238e, check it out and make sure I didn't read it wrong.
Cheers Don...
Don McKenzie
Site Map: http://www.dontronics.com/sitemap
E-Mail Contact Page: http://www.dontronics.com/email
Xbee Wireless Modules, and low cost Interface Boards.
http://www.dontronics-shop.com/xbee-boards.html
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.
I know I'm stating the obvious but have you tried using a humble opamp?
*Peter*Bruce Varley wrote:
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required