3
\$\begingroup\$

I am using a TPS2546 in a USB charging hub, and I'm basing it on a preexisting design I found online (link to writeup for design). In the schematic for the hub design the ILIM_SEL, EN, CTL1, CTL2, and CTL3 pins are all pulled up or down with pullup and pulldown resistors. As can be seen in the photo below.

enter image description here

But, when I went to the datasheet for the TPS2546 it said that no pullup or pulldown resistors are necessary for said pins (as can be seen in the picture below),

enter image description here

If I can get away without having to use extra resistors I would prefer that, but I also do not want to exclude them only to realize that doing that breaks the design somehow. As I am fairly new to this I wanted to ask if anyone on here could see a reason why the hub design uses resistors, when the datasheet says they are not necessary, and if you would recommend I include them, or if its okay that I leave them out.

\$\endgroup\$

1 Answer 1

6
\$\begingroup\$

Placing those resistors is not necessary, as stated in the datasheet, but doing so brings flexibility during R&D stage i.e. it becomes much easier to tie the pin to GND (via a piece of wire, for example) just to see what happens. But if you tie the pin directly to VIN you won't be able to tie it to GND without cutting the connection/trace.

Some designers leave space for both pull-up and -down resistors on the PCB (by placing simply a resistor footprint) for extra flexibility, but populate only one of them for product release and production.

If you are sure that you won't change/modify the connections then you can just tie them directly to VIN or GND.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.