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High impedance output to control on-off state

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strahd_von_zarovich

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Hi, i have 2 DC-DC converters which i want to control their on-off state. However, one of them is at on-state when i apply 3-12V or open circuit and off-state when i apply 0-1.2V. Other one is at on-state when i apply open or high impedance and off-state when 2...4 mA current applied via 1KOhm resistor. I want to control them with one circuit and one logic. How can i do that . İ am planing to use open collector transistor design, but high impedance part is confusing me :-| . I have 5V logic high, which i am planing to apply first DC-DC converter, but with same output how can i control other DC-DC converter. :roll:
 

Hi,

A switching open collector circuit has two output states:
* high impedance
* low impedance (short) to GND.

For the first supply a typical open collector is the way to go.

For the second one, there are informations missing: current direction and typical voltage.
I guess a second open collector with additional current limiting resistor will do.

To save power during OFF state I recommend to use Mosfets jnstead of bjts.

Klaus
 

Thanks Klaus,

Something like in the image may work ?

For the first DC-DC converter i am going to use directly logic state. For the second one i am planing to use same logic to convert high logic or high-z.

High-Z.JPG
 

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