From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-03-29 17:00:31
Hi all,
I've just uploaded a schematic for a serial port powered RS232
transmitter. It looks good up to 500kbps.
http://groups.yahoo.com/group/buildcheapeeg/files/hardware%
20design/RS232TX.gif
Current consumption: Less than +/-3mA at full load (3kOhm/1000pF).
This does not include whatever current the voltage regulators need.
Performance: should work on any desktop PC. Embedded users can scrap
the TTL-to-RS232 level converter.
Laptop users are probably out of luck unless they supply +/-5V
externally and/or uses a RS232 port booster.
Note: Empirical research (not by me) shows that you don't really need
the level converter. Remove it and current consumption drops to <
100uA. Don't expect it to work with 150 ft cables though.
Best source for the MAX987 is Maxim/Dallas Semiconductors, as they
provide free samples and have online ordering.
Joerg: I failed to import the MAX987 into SwitcherCAD, but if you
want to take a closer look at this circuit, I guess you know how!
/Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:43 BST