DS89C386_16 Datasheet, PDF (5/13 Pages) Texas Instruments – Twelve Channel CMOS Differential Line Receiver

DS89C386
www.ti.com
SNLS100C – MAY 1995 – REVISED APRIL 2013
SKEW
Skew may be thought of in a lot of different ways, the next few paragraphs should clarify what is represented by
t_SK in this datasheet and how it is determined. Skew, as used in this databook, is the absolute value of a
mathematical difference between two propagation delays. This is commonly accepted throughout the
semiconductor industry. However, there is no standardized method of measuring propagation delay, from which
skew is calculated, of differential line receivers. Elucidating, the voltage level, at which propagation delays are
measured, on both input and output waveforms are not always consistant. Therefore, skew calculated in this
datasheet, may not be calculated the same as skew defined in another. This is important to remember whenever
making a skew comparison.
Skew may be calculated for the DS89C386, from many different propagation delay measurements. They may be
classified into two categories, single-ended and differential. Single-ended skew is calculated from t_PHL and t_PLH
propagation delay measurements (see Figure 8 and Figure 10). Differential skew is calculated from t_PHLD and
t_PLHD differential propagation delay measurements (see Figure 11 and Figure 12).
Figure 7. (Circuit 1) – Circuits for Measuring Single-Ended Propagation Delays
(See Figure 10)
Figure 8. (Circuit 2) – Circuits for Measuring Single-Ended Propagation Delays
(See Figure 10)
Figure 9. Waveforms for Circuit 1 – Propagation Delay Waveforms for Circuit 1 and Circuit 2
(See Figure 8)
Figure 10. Waveforms for Circuit 2 – Propagation Delay Waveforms for Circuit 1 and Circuit 2
(See Figure 8)
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