ULC393

Preliminary

CMOS IC

UNISONIC TECHNOLOGIES CO., LTD

6 of 7

www.unisonic.com.tw

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PARAM ET ER M EASU REM EN T I N FORM AT I ON (Cont .)

Propagation delay time is defined as the interval between the application of an input step function and the instant

when the output reaches 50% of its maximum value. Propagation delay time, low-to-high-level output, is measured

from the leading edge of the input pulse, while propagation delay time, high-to-low-level output, is measured from the

trailing edge of the input pulse. Propagation delay time measurement at low input signal levels can be greatly

affected by the input offset voltage. The offset voltage should be balanced by the adjustment at the inverting input

(as shown in Figure 2) so that the circuit is just at the transition point. Then a low signal, for example, 105mV or 5mV

overdrive, causes the output to change state.

Low-to-High-

Level Output

Input

Overdrive

100mV

Input

100mV

Overdrive

90%

50%

10%

Level Output

High-to-Low-

90%

50%

10%

VOLTAGE WAVEFORMS

Figure 2. Propagation Delay, Rise Time, and Fall Time Circuit and Voltage Waveforms