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Block a load supplied by an LDO

Is there a simple method to block a load supplied by an LDO until the LDO reaches its regulated output? The rise time of the LDO's output is

850uS (22uf output cap). The load is only 10mA. I've tried using a P-FET between the load and the LDO no luck. I've tried a few things. I won't bore you with them.

If anybody has a suggestion Thanks.

Reply to
Hammy
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What about using a supervisor chip (e.g., MCP130 or MCP100) as the trigger? Use the *Reset out line to gate a logic-level FET with a low Ron at the available Vcc.

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Rich Webb     Norfolk, VA
Reply to
Rich Webb

Thanks .I never heard of them before.Pretty cheap to.

Reply to
Hammy

Sample the input voltage to the regulator and use a comparator to hold a P-channel MOSFET OFF until VIN has been stable long enough for you to know that the output of the regulator is where it's supposed to be.

View in Courier:

PCH VIN>--+-----+---+----+---[LDO]----S D---+ | | | | | G | [Rt] [R1] | [R] | | | | | | | | | | +-----|--|-\\ | | | [LOAD] | | | >--+-----|--------+ | | +--|+/ | | | | | | | [Ct] [R2] | | | | | | | | GND>--+-----+---+----------+--------------+

BTW, what are the LDO's input and output voltages?

JF

Reply to
John Fields

Hi John

It's a 9V battery so about 9.5-6.5V in; and 5.6Vdc out. I went with the 5.6vdc out so I could just use diodes as cheap reverse polairity protection on the loads.

I have everything I need to try your circuit tommorrow. I'll let you know how it goes.

Thanks

Reply to
Hammy

Thanks John worked like a charm!

Reply to
Hammy 

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:-)

JF
Reply to
John Fields

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