Circuit/PCB TSSP58038 to 8NOR gate

Other Hardware General Electronics
1

Can someone take a look at this and confirm I've got my ratlines right for the circuit? I'll route it (and add the other 6 inputs identically) if so. Thanks :slight_smile: I'm reading 8 TSAL6200s pulsed at 38khz, into a single beambreak.

Edit - I got VSS/VDD backwards on the norgate, easy to fix. More concerned about how I connect the rest.

pcbNORgate.png
pcbNORgate.png1402×920 243 KB

2

Formally it is correct. However, there are several things to consider:

  • Capacitors 0.1uF belong to TSOP. There is no point to put all capacitors in parralel in one spot, capacitors should be placed as close to TSOP as possible, one TSOP - one capacitor.
  • It is a good idea to add one more 0.1uF capacitor; it should be between U1 pin 8 and pin 14. Place it close to U1.
  • It is not much point to place many 100 Ohm resistors in parrallel. You need just one resistor instead; for 8 TSOPs it should be about 10 Ohm. You can place that resistor anywhere you like.
  • I think that the original circuitry (on the left) with a single TSOP would be perfectly good for reading 8 TSAL6200s; at least it will be as good as your circuitry with 8 TSOPs placed on one board.
3

Perfect, thanks. But I"m not understanding the caps - they're not directly on traces with the TSSPs. Is it something that just works with proximity? And for clarity, the TSSPs won't be on board - the leads will head off board, and they'll be at various heights on a light-curtain.

4

Yes, each integrated circuit (eg each TSSOP and U1) needs a decoupling capacitor at its supply rail in close proximity. Without a capacitor nearby it might malfunction. Decoupling capacitor needed to supply peak current to integrated circuit.

5

No you can not parallel up those capacitors and resistors. Each TSOP requires its own 100R and capacitor. It is called supply decoupling, you can only start to common up at the 5V rail.

6

dirtyharry2:
Perfect, thanks. But I"m not understanding the caps - they're not directly on traces with the TSSPs. Is it something that just works with proximity? And for clarity, the TSSPs won't be on board - the leads will head off board, and they'll be at various heights on a light-curtain.

Absolutely works with proximity, they are decoupling on the supply and work at nanosecond
timescales. The capacitor for each chip needs to be right on its supply pin within a cm if possible.
No point at all if they are on a different board!
Always use wide traces for power and a ground plane for ground if at all possible, this will really
improve supply decoupling. The wide supply trace is for low inductance, the resistance is not
normally the issue at all.

7

Yes the resistor is an issue with these devices. At one place I worked one team left it out which lead to a catastrophic failure, that is over a 5% fail rate and several thousand boxes had to be returned.