Re: **LOW** Power applications

In article <1157390698.941191.230410@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
linnix <me@xxxxxxxxxxxxxxxxxx> wrote:
[...]
The trick is power management. At 10mA, the Max232 is drawing several
time more power than the micro at idle. I am redesigning my circuit to
turn it on only when a cable is connected (A2D the DTR signal). The
Max232 (started out at Maxim, second sources from many) is about $1,
but it requires 4 1uF caps (a penny each). Siplex actually has a part
with build in caps, but they wants $3 each.



You can power the output circuit from the connected RS-232. This would
require that you not use the MAX232. I'm thinking along these lines:


!!-- Vcc
From micro -------!! P-MOSFET
!!--------+-------------- TXD
!
\
/
\
! C1
+--!!--GND
!
V
---
!
------------+--------------- RXD


If Vcc is at least 3V, this will work. With the RS-232 cable not plugged
in, the circuit floats and only the leakage in C1 matters. The P-MOSFET's
leakage is taken out of the picture.


--
--
kensmith@xxxxxxxxx forging knowledge

.

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