how to protect external mcu when applying 2 power sources

Discussion in 'General Electronics Chat' started by ghisbo, Apr 18, 2018.

  1. ghisbo

    Thread Starter New Member

    Apr 18, 2018
    1
    0
    upload_2018-4-18_14-30-35.png
    Setup: an external MCU is connected via a DIN Connector (// par lines) to the NTC temp sensor. It applies a voltage of 3.2V over a 2.2K resistor.
    the internal MCU is reading the same value of that voltage over the NTC.
    - When the external MCU is not connected, the internal MCU needs and internal VCC to be applied ( symbol SWITCH)
    - The voltage of the internal VCC is not the same as the external.
    - How can i prevent that the ext MCU get's damaged, or get's false readings.
    - the external MCU can be plugged in or disappear at any time;
    I taught to put a diode in between A and B, but then there is the Forward Voltage drop that will influence the readings.

    Thanks in advance for your attention
     
  2. danadak

    Distinguished Member

    Mar 10, 2018
    3,497
    785
Loading...