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SN74HC595: Are my chips defective?

Gregory Mooney
Prodigy 20 points
Part Number: SN74HC595

I bought 4 of the chips from Mouser and none of them work. They said to try to get help here. I'm not sure why. 

 I already own one of the 74HC595 chips and it works good. I built a circuit to test it. Then when I put the new chips in, they didn't work.

Are some chips just bad or am I doing something wrong? I have positive and ground connected to pins 16 and 8 respectively. I have pin 13 output enable tied to ground. I tied pin 10 high, and put my clock to pin 11.  Serial pin 14 I have connected to a momentary push button switch that is pulled down to ground with a 10k resistor until it is pushed, then it goes to the positive rail. All of the Q data pins are connected to 330 resistors then to the positive leads of LEDs to test. 

This configuration works fine with the 74ls595 chip I got with a Virulos Arduino kit, but not with the 595's I got from Mouser. Any suggestions about what the problem may be, or should I just have Mouser send me 4 new ones or order from a different company? I thought it may be my clock pulse at first, but the data sheet I have says that there is not maximum clock value associated with this, so the 200 ns pulse I have set on my 555 timer should be working.

Thanks

  • 0
    Guru 316690 points

    What voltage are you using? If you don't have a schematic of your circuit, can you show at least a photo?

    You did not mention RCLK (pin 12). A CMOS input must not be left open, or it will float; and you need a rising edge on RCLK to copy the shift register to the storage register.

    Is your original chip LS or HC?

  • 0 in reply to Clemens Ladisch
    Prodigy 20 points

    Thanks.

    I think my problem was with RCLK. I tied it to SRCLK and now it works. I should have read the datasheet more completely. However, I didn't need to connect RCLK with my original 74HC595. Strange. 

    But yes, all the 74595 chips I have are HC.