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Bistable multivibrator using 555 timer

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Why the initial state of Bistable multivibrator using 555 timer is coming high?

 

I want to make a circuit for triggering the STM32 microcontroller into the Bootloader mode. For normal operation of MCU using flash memory the BOOT0 pin should be low and for entering the bootloader mode the BOOT0 pin should be pulled high. Presently I am using Bistable multivibrator using 555 timer. The output of bistable multivibrator is connected to BOOT0 pin.



Initially on power up, the output of the bistable multivibrator should be low but in my circuit it is coming high because of which my MCU by default is entering in bootloader mode.



Why on power up the output of circuit is coming high and what can I do for output to be low initially?

 

bistable_multivibrator.png

Sourav Gupta

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Could you add a pull down resistor of 1k and check the output?

   Joined February 12, 2018      696
Monday at 02:11 PM