Re: Clamping to Linear regulators

On Wed, 03 May 2006 14:38:29 GMT, "AJ" <itisme33@xxxxxxxxxxxxxx> wrote:

Thanks to everyone for their feed back. The 3.3V rail should have at least
20ma load on it all the time and I also have a 3.6V TVS diode on the rail
which I was hoping would prevent the voltage rising. Do you think this
would be ok or should I add the OP AMP?


Unless you are clamping a LOT of 24V/100K loads to the 3v3 rail it would be fine. The only problem
arises when the current you are sinking is more than the load current, in which case the regulator
would cease to be conducting and the voltage could rise.
As long as there is enough load, the sink current just makes the regulator push slightly less harder
to maintain its 3.3v output.


Regards


AJ

"Mike Harrison" <mike@xxxxxxxxxxxxxxx> wrote in message
news:misg521vm3m4866646l1gfd7nj26grsrl0@xxxxxxxxxx
On Tue, 02 May 2006 15:48:01 GMT, "AJ" <itisme33@xxxxxxxxxxxxxx> wrote:

Hi,

I have a 3.3V linear regulator that I want to use to clamp 24V to via a
100K
resistor and a diode. Im pretty sure this is ok but just wanted to double
check. Does anyone have any feedback?



Depending on the load, it could potentially drag the 3.3v rail upwards.
A more universal solution would be to use an opamp set as a unity-gain
buffer, powered from the
supply into the 3v3 reg, with the input from the 3.3v supply.


.

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