In

Figure 2, VX, where X is a number, is the waveform volt-

age level at which the propagation delay measurement ei-

ther starts or stops. Furthermore, V1 and V2 are normally

identical. The same is true for V3 and V4. However, as men-

tioned before, these levels are not standardized and may

vary, even with similar devices from other companies. Also

note, NC (no connection) in

Figure 1 means the pin is not

used in propagation delay measurement for the correspond-

ing circuit.

The single-ended skew provides information about the pulse

width distortion of the output waveform. The lower the skew,

the less the output waveform will be distorted. For best case,

skew would be zero, and the output duty cycle would be

50%, assuming the input has a 50% duty cycle.

For differential propagation delays, V1 should equal V2. Fur-

zero volts on the differential waveform (see bottom wave-

form in

Figure 9). This is true whether V3 equals V4 or not.

However, if V3 and V4 are specified voltages, then V3 and

V4 are less likely to be equal to the crossing point voltage.

Thus, the differential propagation delays will not be mea-

sured to zero volts on the differential waveform.

The differential skew also provides information about the

pulse width distortion of the differential output waveform rela-

tive to the input waveform. The higher the skew, the greater

the distortion of the differential output waveform. Assuming

the input has a 50% duty cycle, the differential output will

have a 50% duty cycle if skew equals zero and less than a

50% duty cycle if skew is greater than zero.

Complementary skew is calculated from single-ended propa-

gation delay measurements on complementary output sig-

they are relative values.

The complementary skew reveals information about the con-

tour of the rising and falling edge of the differential output

Waveforms for Circuit 1

DS012086-11

Waveforms for Circuit 2

DS012086-12

FIGURE 7. Propagation Delay Waveforms for Circuit 1 and Circuit 2 (See

Figure 6)

(Circuit 3)

DS012086-13

FIGURE 8. Circuit for Measuring Differential

Propagation Delays (See

Figure 9)

Waveforms for Circuit 3

DS012086-14

FIGURE 9. Propagation Delay Waveforms

for Circuit 3 (See

Figure 8)

(Circuit 4)

DS012086-15

FIGURE 10. Circuit for Measuring Complementary

Skew (See

Figure 11)

Waveforms for Circuit 4

DS012086-16

FIGURE 11. Waveforms for Circuit 4 (See

Figure 10)

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