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LM2901B-Q1: Response time

Chuqiang Wen
Expert 6310 points

Part Number: LM2901B-Q1
Other Parts Discussed in Thread: LM2901B

Hi team, 

I don't quite understand the test condition on response time as below. What is the detailed difference between TTL level input step and 100mV input step? How they casue much difference on response time? 

image.png

Thanks!

Ethan Wen

  • 0
    Guru 325400 points

    TTL is just a much larger overdrive (typically 3000 mV). See figures 5-25…5-32 for how the device behaves with different overdrives.

  • 0
    TI__Guru 68346 points

    Hi Ethan,

    As Clemens showed, the "TTL" input is a full 5V input TTL signal (1970's TTL levels), which is a HUGE overdrive. 5V - 1.4V = 3.6V overdrive.

    Technically, a 0 to 5V input on a 5V supply violates the (VCC-1.5V) input range, but the overdrive is so large it saturates the inputs and overrides the effects.

    In short, the "TTL" input is the fastest the LM2901B can achieve...