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Interfacing IC (LT1158) with FAULT and ENB to a uC (AVR)

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mriksman

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Well, I have been banging around the Internet learning (well I thought I was), about diodes, and protection and so forth; and I am pretty sure I have just confused myself.

Could someone check out this schematic I drew, check some of the comments, and tell me if I am about to blow something up!?

circuit.JPG

I am particularly curious about the diode D3. If the ENABLE pin is holding 7.5V, and I have STOP held HIGH, then won't the diode be forward biased, and current flow into the uC?

So confused...

If anyone does have comments, I'd love to know the theory behind it so I can learn something from this.

The IC is compatible with 5V logic. There is a comparator just after the ENABLE pin components (not shown here, but you can see it in the datasheet) that checks to see if it is above 1.4V. When ENABLE is pulled low, it discharges to below 1.4V and the chip becomes disabled. When left floating, it is charged via the 25uA current source up to a clamped 7.5V to ENABLE.

I would like it so;
* the IC can self disable itself when a FAULT occurs. This is handled simply by connecting FAULT to ENABLE. A resistor could be used to manipulate the discharge time.
* A separate uC disable (STOP in the diagram) so I can disable the IC chip myself.
* The ability for the uC to read the status of the FAULT line on the IC.

Thanks again.
 

mister_rf

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Try this way
 

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