MCU to ADC hardware connection

Discussion in 'Embedded Systems and Microcontrollers' started by tigerk2001, Jan 8, 2010.

  1. tigerk2001

    Thread Starter New Member

    Jan 7, 2010
    8
    0
    Hi,
    I have a MCU working on 3.3volts and I want to communicate with a ADC that work on 0-5volts range. Can someone give to me the best way to configure my hardware for CS, SDO, SDI, SCK?
    thanks for your help
     
  2. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    1,015
    69
    It may work directly.

    Many 5V circuits only need 2V for the logic High level ('TTL' Levels) - check the datasheet for the ADC and use pullups to the 3.3V supply to ensure the best possible High level.
     
  3. tigerk2001

    Thread Starter New Member

    Jan 7, 2010
    8
    0
    You're right,
    I use a LTC2414 from linear as ADC and his high level is 2.5v and low level is 0.8v.
    However, since my ADC VCC and ref is 5V, the problem will come from the SDO of the ADC. If it goes to 5v to the MCU GPIO, it may damage the MCU.
    It is why I'm wondering if it is necessary to use a voltage level translator like ST2378 or equivalent.
    Also, in the case I go directly, is there any buffer to install or I can go directly from the MCU to the ADC?
    Thanks
     
  4. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    You could put a few diodes in the path. Each silicon diode will drop 0.6V.
    The logic high from the ADC will most likely be less than 5V anyway, check the datasheet. It's probably 4-4.5V.
     
    Last edited: Jan 9, 2010
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