• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 18 subscribers
  • Views 164 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN74AHCT541: What is the VCC minimum threshold to working normally?

Zoe Yang
Intellectual 2210 points
Part Number: SN74AHCT541

Dear team,

My customer is using SN74AHCT541 as buffer to PWM signal. When designing STO function, they use a voltage monitoring to measure VCC of SN74AHCT541 when it drops to the minimal normal working voltage and considering it a STO function. 

Our datasheet claims that Vcc ranging from 4.5V to 5.5V. So would you please help comment on what is the minimum threshold of VCC to working normally? Or do we have FMEDA file to illustrate? Thanks!

  • 0
    TI__Guru* 96681 points

    Hi Zoe,

    Zoe Yang said:
    When designing STO function, they use a voltage monitoring to measure VCC of SN74AHCT541 when it drops to the minimal normal working voltage and considering it a STO function.

    What is an "STO" function?

    Zoe Yang said:
    do we have FMEDA file to illustrate?

    There won't be an FMEDA for a non-automotive device like this.

    Zoe Yang said:
    Our datasheet claims that Vcc ranging from 4.5V to 5.5V. So would you please help comment on what is the minimum threshold of VCC to working normally?

    The SN74AHCT541 is a TTL-compatible CMOS logic device. TTL-compatible explicitly means that the input signal has VIL = 0.8V and VIH = 2V, while the output is 0 to 5V.  This is the reason that the device is specified from 4.5V to 5.5V -- ie that is the TTL-compatible voltage range.

    This does not mean that the device cannot function below 4.5V, however it does mean that the device was only specified for operation between 4.5V and 5.5V.

    We do not specify a minimum functional voltage for the majority of logic device beyond the recommended operating conditions table -- ie that is not part of the characterization for most logic parts.

    Generally speaking, a CMOS logic device only requires that there is enough voltage to bias all the internal transistors to the 'on' state. This is usually between 1V and 1.5V. The higher the voltage, the better the transistors will work (up to the point where they are damaged to to excessive voltage).

    We do not recommend using the device outside the recommended operating voltage range, but there is nothing stopping a customer from operating one of these devices at 2V or 3.3V.