[TriEmbed] I need a circuit that can do this.....

Michael Monaghan mike at chipworks.net
Wed Jun 22 05:56:25 CDT 2016


Chip.

Since there are never enough ways to skin a problem...

The _LE on the MAX is "hold current output" and your design requires "hold
detection until reset".  With an inverter you should be able to drive _LE
from OUT.  IIRC a pair of NORs should get you a "hold detection" latch with
the ability to reset from a uP without sleep killing the whole deal.  The
low pass filter on input is an excellent idea in this configuration.
What's your uP and are outputs HiZ when sleeping?

Mike

On Tue, Jun 21, 2016 at 8:49 PM, Chip McClelland via TriEmbed <
triembed at triembed.org> wrote:

> All,
>
> OK, before you say it, yes, I first consulted Google before sending this
> note.  I have not worked with these devices before and the latch operation
> is the part that I find most confusing. The best device I could find was
> the MAX9141
> <https://datasheets.maximintegrated.com/en/ds/MAX9140-MAX9144.pdf> but
> the operation of the latch in figure 2 was not what I expected.
>
> I am looking for a simple circuit which will do the following:
> - Powered, Vcc, by either 3.3V or 5V and should not consume more than
> 100uA.
> - Connect to the analog output  (ranges from 0 to Vcc) of my Ultrasonic
> Range Finder <http://www.maxbotix.com/Ultrasonic_Sensors/MB7363.htm> with
> a high input impedance - potentially with a low-pass filter - we will see.
> - Allow me to set a “trigger threshold” ( 0 to Vcc) using a potentiometer
> - Compare the input to the trigger and provide a latched digital “high”
> when the input exceeds the threshold
> - This signal will wake the micro controller using a hardware interrupt
> and trigger an interrupt routine.
> - The comparator will hold the line “high” input until cleared by the
> micro controller
>
> Anyone who has a few minutes to take a look please let me know:
> - Is the part I found the right one?
> - Is there a better solution - perhaps using discrete components?
>
>
> Thank you,
>
> Chip
>
>
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