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AM26C32: Operational Datarate

Darren (FAE)
Expert 5483 points
Part Number: AM26C32
Other Parts Discussed in Thread: AM26LV32

I have an application considering the AM26C32I/C devices for use as a Quad Receiver.

There is a Line Driver that buffers some CLK and DATA signals (converting to differential). The Quad Receiver receives these differential inputs, and outputs the result to some device for processing.

The TI Online Web Tool seems to list the AM26C32I/C devices as having a 10Mbps limitation, but I don't see that in the datasheet anywhere.

1) In an application where there is no cabling between driver/receiver IC's, and trace length is kept to a couple of [cm], would the AM26C32I/C be able to support 25Mbps?
The DS lists the output rise/fall times, with a MAX of 10ns. If you assume a full cycle (Rise->Fall->Rise->Fall), that is 4x 10ns = 40ns for a "Period"
1 / T = f, so for 40ns we get 25Mbps worst case, with 50pF of bus capacitance at MAX operating temp conditions, according to the DS.
So, is it safe to say the device can support up to 25Mbps?
Or, is it somehow limited to how the detection circuit for the input differential waveform works? If so, could you explain?

In this specific application, the Propagation Delay times and Enable delay times don't matter.

-Darren

  • +1
    Guru 316690 points

    Mbps is not MHz. When measuring Mbps, one bit time is the time between two signal edges. So 10 ns would correspond to 100 Mbps or 50 MHz.

    However, using the rise/fall time is likely to overestimate the speed limit. In the absence of other information, you should use the propagation delay time (which will underestimate the actual limit): 1 / 27 ns = 37 Mbps = 18.5 MHz. I do not know why the search function and the product page list then AM26C32 speed as 10 Mbps.

  • +1
    TI__Mastermind 25705 points

    Darren,

    Clemens' comments about using the prop delay for estimate make sense for this case. For comparison, AM26LV32 (marked 32MHz in the datasheet) has the 20ns max delay.