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TLC374: TLC374IDR Response Time Discrepancy

Brian Wang0928
Genius 14850 points

Part Number: TLC374
Other Parts Discussed in Thread: LM339, LM339B, TLV1814

Team,

The customer is experiencing a discrepancy when testing the TLC374IDR's response time. Their measured results do not match the TTL-level input step specification listed in the TLC374 datasheet, which shows a typical value of 200 ns as show below.
TLC374-1.png

Test Configuration:

  • INVR1_PWM_L1: Signal from FPGA's GPIO
  • INVR1_COM: TLC374's output

TLC374-12.png

Issue: The customer's experimental results show a turn-on delay of approximately 400 ns (measured from INVR1_PWM_L1 to INVR1_COM), which is 2x the typical datasheet specification of 200 ns.

Comparative Testing: When using the same circuit configuration with a competitor's part (ST LM339DT), the response time measures approximately 300 ns, which aligns closely with the LM339 datasheet specification.

TLC374-123.png

Customer's Question: Why is the TLC374IDR's measured response time (400 ns) significantly higher than the datasheet typical value (200 ns), while the competitor's LM339DT performs closer to its datasheet specifications?

Regards

Brian

  • 0
    Guru 321080 points

    The TLC374 (like the LM339, which it was intended to replace) has different response times for high-to-low and for low-to-high transitions. As far as I can see, the response time specified in the datasheet is some average of these two cases.

    When comparing against ST's LM339, consider the LM339B:

     

    If you want symmetric switching times, consider a comparator with push/pull outputs like the TLV1814.

  • 0
    TI__Genius 13225 points

    Hi Brian,

    Could you provide me a bit more information on this issue?

    • Are you seeing this discrepancy in propagation delay on multiple TLC374IDR? Does this discrepancy happen across different devices/boards?
    • What voltage is the VDD of the TLC374IDR?
    • Is the 100pF capacitor at the IN+ of the TLC374IDR critical to the customer's application? If it isn't, could you please try measuring the propagation delay with it depopulated since it is slowing down the input rise time of the TLC374IDR IN+.

    Since the TLC374IDR has been PCN, please provide me an image of the shipping label so that I can run the lot to confirm the die.