# Determine the min/max resistance of an SMD variable resistor

I want to determine my minimum and maximum resistance rating for my variable resistor but failed to find the relevant information in the datasheet (this might be an issue more 'noobs' might have, therefore the question here).

1. I chose a SMD Variable Resistor (LCSC link) rated at 15kΩ because it's close to the desired range (24-33kΩ), and because it's assembled by JLCPCB (and in stock).
2. Where in the datasheet (link) do I find the minimum and maximum resistance, approximately (standard environment)?
3. (Are there general 'rule-of-thumbs' for variable resistors when it comes to min/max resistance ratings?)

Background (to avoid XY problems):
I want to regulate 3.7-5V -> 3.3V (either from lipo or usb port), I determined STI3408B is a good choice: it provides up to 1.2A and has a somewhat low quiescent current of '40µA' (I'm sure that's variable depending on multiple factors I'm currently unaware of) and it doesn't have the thermal issues as linear regulators. Using a similar component, I measured my reference voltage to be around 0.7V (using off-the-shelf multimeter), not 0.6V as in the datasheet. I'm unsure if (or why) this is really an issue, but to minimize the potential of errors (that require re-soldering), I concluded a variable resistor for R2 would be suitable, the formula to determine the output of the IC seems to be fairly standard (see below), where Vout is between 2.6-3.6V (esp32) and I planned R1 to be 110kΩ. Since it is a 15k potentiometer, ideally it will have exactly 15k resistance between ends, and when the wiper is at one end, there will b 0 ohms between wiper and end, and of course 15k from wiper to the other end.

But components are never ideal.

The datasheet says that the resistance is 15k with a tolerance of 25%.

And the wiper to end resistance is 2% from the 15k at most.

• oh, so the rating always references the maximum resistance... that makes sense, thank you. The tolerance of 25% is specified, I took note. Thank you for the kind answer Jun 26 at 11:11
• No, not always. The datasheet says for potentiometers above 1k it is 2% of the total, but for pots less than 1k it is 20 ohms max. Jun 26 at 11:13
• I'll scan the datasheet for this, simply couldn't extract what you just mentioned Jun 26 at 11:14
• clearly, if I want to reach e.g. 35kOhm, I'll need a higher-rated variable resistor Jun 26 at 11:16
• Yes, you would not buy a 15k pot if you need 35k. You would buy a 47k pot. Jun 26 at 11:18