- Fri Sep 09, 2016 1:04 pm
#54757
Do people have strong opinions on the correct values for the various pull-ups and pull-downs? My current design uses 3K9 resistors for all of them (because I had a reel of them) but I am wondering if there might be a good reason to change to something else, say 10K?
- Fri Sep 09, 2016 2:02 pm
#54764
I'm suggesting 10K, but 3K9 is good too, but it is consuming a bit more when shorted to opposite state.
- Sat Sep 10, 2016 5:21 pm
#54830
Sometimes it's a matter of taste. 
I have used 10K for many years if I don't have a reason for a specific value. If I am designing a product at work I will typically use a value that I did have to use. For example, I use 22K on the reset line on PIC processor, and If I wasn't required to use a 10K elsewhere on the circuit I would then just use 22K because I already have to add that part to the bill of material list.
Now if I were to have OneWire devices in the design then I would have used a 4K7 pull-up there. And since I had used the 4K7 already then I would likely use that for any unimportant pull-ups.
I have been using the 4K7 a lot more in my experimentation. Using it on the I2C lines. I typically had used only 2K2 there in order to ensure better speed but recently for my projects I have used the 4K7 in case I wire in a couple of modules that have 4K7 on each device, and the combined resistance ends up close to the 2K2 that I had historically used.
Some people who are sunning long time off of batteries might go for resistances on the higher end of the spectrum in order to save some precious uA. But for a lot of stuff almost anything will do as long as it isn't too high or too low. And that tends to be a personal choice as well, or the mood of the day.
I have used 10K for many years if I don't have a reason for a specific value. If I am designing a product at work I will typically use a value that I did have to use. For example, I use 22K on the reset line on PIC processor, and If I wasn't required to use a 10K elsewhere on the circuit I would then just use 22K because I already have to add that part to the bill of material list.
Now if I were to have OneWire devices in the design then I would have used a 4K7 pull-up there. And since I had used the 4K7 already then I would likely use that for any unimportant pull-ups.
I have been using the 4K7 a lot more in my experimentation. Using it on the I2C lines. I typically had used only 2K2 there in order to ensure better speed but recently for my projects I have used the 4K7 in case I wire in a couple of modules that have 4K7 on each device, and the combined resistance ends up close to the 2K2 that I had historically used.
Some people who are sunning long time off of batteries might go for resistances on the higher end of the spectrum in order to save some precious uA. But for a lot of stuff almost anything will do as long as it isn't too high or too low. And that tends to be a personal choice as well, or the mood of the day.
