SN74LV123A: 1Q output duty cycle decreased while time elapsed in SN74LV123A

Hi Team,

     My customer air-conditional product line reported an issue in SN74LV123ADR that the Duty cycle of SN74LV123ADR decreased as time elapsed, this issue reported in 2 modules which only 3 modules were tested.

Hardware connection:

    SN74LV123ADR powered by 3.3V, /A connected to GND via 2Kohm, /CLR connect to 3.3V power supply via 4.64Kohm, 100Hz 50% duty square waveform input to 1B;  Rext/Cext and Cext connect as datasheet descripted, RT = 4.64Kohm(1% accuracy), CT = 1uF(10% accuracy)

      Also customer connect 1Cext to GND, and the test result is similar, the 1Q output duty cycle is decreased while time elapsed: from 48% decreased to 45% within 20min;

Support Need:

1. Reason that 1Q duty cycle decreased while time elapsed;

2. Comments on which part of schematic should be modified to keep the duty constant;

Best Regards

BenjaminSN74LV123ADR duty decreased when time elapsed.docx