Method for measuring the propagation times of a three-state circuit when the latter passes from a given state to the high-impedance state

摘要

The method of the invention applies to the measurement of the propagation times TpHZ and TpLZ, these times being given for a specified load circuit with a specified capacitance Co. The measurement is made with an automatic tester having an input capacitance C which differs from the specified capacitance, and the propagation time TpHZ corresponding to the specified capacitance is determined with the aid of the algorithm TpHZ = t1 + R DELTA C Log VOH/VOH - 0.5 in which t1 is the measured time, DELTA C = Co - C, R is a resistance in parallel with the input capacitance, VOH is the output voltage from the circuit in the high state. The propagation time TpLZ is determined, after measurement with the tester, with the aid of the algorithm TpLZ = t2 + R' DELTA C Log U - VOL/U - VOL-0.5 in which t2 is the measured time, DELTA C = Co - C, is the output voltage from the circuit in the low state, R' = R'1R2/R'1 + R2 and U = R2 Vcc/R'1 + R2 R'1 and R2 being resistances in series, R2 being in parallel with the input capacitance and R'1 being connected to the positive voltage Vcc. The tester includes a calculator which determines the propagation times from the measured times and from the algorithms and from the values of the terms of the latter previously stored. IMAGE