Problem with 74ls373N as small voltage turns on outputs

[stoyanoff]

Hi! I want to use 74LS373N with a microcontroller(PIC). So I connected the chip to 1 of the ports and I put 4.7k ohms pull-down resistors on every data input of the 74ls. But I have a 0.4-0.5V on every pin and my chart is not working stable. I put 2x 4700uF caps, 1x 100uF and 1x 100nF cap on the power supply. I suppose it`s stable. The problem is this small voltage some how is detected from the chip and it turns on its outputs.
I have connected 7 segment indicator after the 74LS373 and if I manually turn on one of it`s imputs(sometimes) it turns on every 8 outputs.
Can you tell where could be the problem??
Thanks!

 

[DeLorean]

Re: problem with 74ls373N

A 4.7 K pull down is probably to high a value for LS chips. Use a lower value or use a HC or AC chip.

From memory the 373 is a latch. Why not use a 374 which is edge triggered.

 

[pjmelect]

Re: problem with 74ls373N

The 74LS373 is a transparent latch, pin1 should be low to get a output, and pin 11 should be high to make it transparent, that is for a change of input to change the output. A low on pin 11 will latch the output so that a change on the input will not effect the output.
Why use the 4.7K pull downs? A PIC is more than capable to drive the 74LS373 directly