• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 19 subscribers
  • Views 252 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.

SN74LVC3G14: Troubleshoot

Ray Vincent Aranzaso
Genius 14685 points
Part Number: SN74LVC3G14
Other Parts Discussed in Thread: SN74LVC3G17,

Hi,

Good Day. I have a customer who is working with SN74LVC3G14 and SN74LVC3G17. Please see below his query for your reference. Thank you very much.

I am currently troubleshooting an interface PCB that uses both SN74LVC3G14 and SN74LVC3G17 (driver and inverter). Both components are set up to function similar to a differential driver. The issue that we encounter is that at around +85°C, the output of the G14 begins to oscillate, and eventually outputs continuous voltage of VCC regardless of the input signal. The device receives TTL signal from a function generator at both inputs, and thus should see a TTL signal at the output. I checked the datasheets for both devices and the operating temperature is noted as -40°C and +125°C in open space. We are operating the device within the temperature spec.

Best Regards,

Ray Vincent

  • 0
    Guru 262920 points

    This device does not have TTL-compatible inputs. But it is likely that the input signal is not actually TTL.

    Please show the schematic, and specify the voltage levels of the input signals.

  • 0
    TI__Guru* 96681 points

    Hey Ray,

    In addition to the schematic and voltage levels Clemens requested, can we also get scope shots of the SN74LVC3G14, input and output, when operating normally and when the issue arises?

  • 0 in reply to Emrys Maier
    TI__Genius 14685 points

    Hi Emrys,

    Good Day. Please see below the latest response of our customer to your reply. Thank you very much.

    I'm attaching screenshots of an example setup (based on the actual circuit) on LTspice along with the simulation results of the LTspice setup. Of course, these results are ideal and do not account for temperature or other external factors, but this should give a general understanding of the result I expect to get from using these TI components.

    I will follow up with oscilloscope data of the actual setup at varying temperatures very soon.

    Best Regards,

    Ray Vincent

  • 0 in reply to Ray Vincent Aranzaso
    TI__Guru* 96681 points

    Hi Ray,

    My guess would be that the issue is related to the diode operation over temperature:

    The exact output voltage will heavily depend on the diode's performance.

    Additionally, the thresholds for the 1G14 and 1G17 can shift with temperature (see the datasheets for the limits). The combination of changing the input voltage and changing thresholds could easily result in the output no longer switching across temperature. Check that the input signal is still meeting the datasheet specs for the LVC1G14 at 85C.