MC10E1651

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6

DELAY DISPERSION

Under a constant set of input conditions comparators have

a specified nominal propagation delay. However, since

propagation delay is a function of input slew rate and input

ECL and TTL levels, respectively).

Figure 4 and Figure 5 define a range of input conditions

which incorporate varying input slew rates and input voltage

overdrive. For input parameters that adhere to these

constraints the propagation delay can be described as:

accounts for nonuniformity introduced by temperature and

voltage variability, whereas the delay dispersion parameter

takes into consideration input slew rate and input voltage

overdrive variability. Thus a modified propagation delay can

be approximated to account for the effects of input conditions

that differ from those under which the parts where tested. For

example, an application may specify an ECL input with a

slew rate of 0.25 V/NS, an overdrive of 17 mV and a

temperature of 25°C, the delay dispersion parameter would

be 100 ps. The modified propagation delay would be

775 ps ± 100 ps

Figure 4. ECL Dispersion Test Input Conditions

Figure 5. TTL Dispersion Test Input Conditions

0 V

0.5 V

2.0 V

2.5 V

− 1.75 V

− 1.58 V

− 1.07 V

−0.9 V

SLEW RATE = 0.75 V/NS

SLEW RATE = 0.75 V/NS

SLEW RATE =

0.25 V/NS

SLEW RATE =

0.30 V/NS

INPUT

THRESHOLD

RANGE

INPUT

THRESHOLD

RANGE