We are using p/n: SN74HC595D in our boards more than 5 years. All the while this part is working good & we did not face any issue with the part.
As per our system design, once power up our system, SN74HC595D IC’S all the output pins (Qa to Qh) will go to low state immediately without any delay. But in the recently received lot, few ICs are behaving bit different, means all output pins are going low state immediately except Pin Qa. Pin Qa is going low state after 1 second delay. In this type of boards once replace another IC, board is working good (Means all output pins are going low state immediately without any delay including pin Qa).
Please let me know why some ICs are behaving bit different? only one output pin is going low state with one second delay?