Termination and Conditioning

You must terminate a signal so that the line doesn’t float. For example, when data lines transitions from logic low to logic high, the level shifter opens similar to an open switch. The pullup resistor pulls the voltage up to logic high so that the signal can continue. Tables throughout this document provide the size of the pullup resistor you need for each signal.

The following diagram shows how the values in the tables were measured and what each value means, and an example table.

Example Table

Signal Name Pullup Voltage

Rmin (Ω)

CLOAD (pF) Trise (ns) Tfall (ns)


3.3 2200 47 36800 19


The values in the table present the rise and fall times for a particular capacitive loading. You need to calculate the maximum frequency and values for Vol, Voh, Vil, Vih, Iol, Ioh based on the capacitive loading of your particular design.

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