Automotive voltage level translation from 12V to 3.3V


I have an automotive circuit with MSP430F5438A and there are some inputs to be given to the MSP from the automobile electronics.

All the inputs will have 12V and for MSP430, they need to be shifted to 3.3V. Also the current in those inputs can be pretty high, ranging from 500mA to 1 or 2A.

Is there any IC that could be used?

I have looked at TLC27L4, CD40109B-Q1.

Can anyone provide an expert opinion on which one to use? Also if any other solutions available??


6 Replies

  • Hi Shashank,

    Firstly I am not an expert, but I would suggest you the following:

    As you mentioned in your post the circuit is automotive I suggest to isolate you controller from the inputs. As I can see the high voltage and current ratings of 12V and 1Amps. I think you should got with two stages.

    1: Use resistor dividers to bring down your voltage to 5.0V and take care of current rating while designing your divider circuit.

    2: Use digital isolators with one side operating @5.0V and other side operating @3.3V, with lower voltage side connected to your controller.

    There are some other replacements of divider, that can be implemented using opamps if you want.

    Refer the thread:

    Thanks and Regards


  • In reply to Anand Kumar Rai:


    we are in industrial and we search circuit to convert logic signal 12v to -> 5v
    Did it exist circuit do do this in ti ?
  • In reply to yohann wypiorczyk:


    The portfolio that I am responsible for does not have such a product at this time.

    However, I did a product search to screen out translators that support at least 12V. The results are shown at the bottom of this message.

    For each of these devices (CD40109B, CD40109B-Q1, and CD4504B), if VCC > VDD, then they will operate as a high-to-low level translator. The propagation delay measurements in the datasheets also includes test cases of high-to-low traslation (e.g. 10V to 5V, 15V to 5V). I will assign to the appropriate engineer for verification, incase my understanding is mistaken. Thanks.



    If this post answered your question, please click Verify Answer

  • In reply to Nirav Patel:

    Hi Yohann ,

    These devices will work as high to low voltage translation devices . Basically , all the CD4K series are rated for higher voltage ranges upto 18V and can be used . I would be concerned on the input current since these are CMOS devices with high impedance inputs consuming low input current. Suggest to have series current limiting resistors at the input of the devices . Will this solution work for you ?



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  • In reply to ShreyasRao:

    Hi Shreyas,

    CD40109B-Q1 specifies Vdd down to 3V, but seems to be only characterized at 5V and higher. Do you see any issues using this as a 12V to 3.3V (high-to-low) translator? Application is also interfacing MSP430 with 12V automotive signals. 



  • In reply to Antonio Fadhel:

    Hi Antonio,

    The CD40109B-Q1 won't have any trouble converting 12V down to 3.3V for logic signals, however I have two concerns.

    1. Is this '12 V' logic signal from a regulated 12 V rail, or is this the vehicle's battery voltage?

    2. I'm wondering about your comment on current. Can you explain "Also the current in those inputs can be pretty high, ranging from 500mA to 1 or 2A." In logic, you typically see very low currents. Are you saying that these are inputs that need to sink up to 2A, or that the circuits could supply 2A if allowed to do so?

    If you have a schematic or can explain more about your application, it would be very helpful.

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