LMH7220_14 Datasheet, PDF (18/34 Pages) Texas Instruments – LMH7220 High Speed Comparator with LVDS Output

LMH7220
SNOSAL3E – SEPTEMBER 2006 – REVISED MAY 2013
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Amplitude Overdrive Dispersion
One of the parameters that causes dispersion is the amplitude variation of the input signal. Figure 24 shows the
dispersion due to a variation of the input overdrive voltage. The overdrive is defined as the ‘goto’ differential
voltage applied to the inputs. Figure 24 shows the impact it has on the propagation delay time if overdrive is
varied from 10 millivolts to 100 millivolts. This parameter is measured with a constant slew rate of the input
signal.
Overdrive 100 mV
+
Overdrive 10 mV
0
time
-100 mV
-
Overdrive Dispersion
+
Dispersion
0
time
-
Figure 24. Overdrive Dispersion
The overdrive dispersion is caused by the fact that switching currents in the input stage depend on the level of
the differential input signal.
Slew Rate Dispersion
The slew rate is another parameter that affects propagation delay. The higher the input slew rate, the faster the
input stage switches (Figure 25).
+
0
time
-
Slew Rate Dispersion
+
Dispersion
0
time
-
Figure 25. Slew Rate Dispersion
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