How to set threshold of STEF01 Undervoltage Lockout (UVLO) feature

[Central SUPPORT]

Hello. I am evaluating STEF01 for a PSU application.

I am trying to calculate the values for RH using the formula provided in the datasheet. But my calculation result for RH is not in line with chart given in figure 6 (page 8 of the datasheet). Referencing the chart, for a value of RL of 10K, and a required UVLO of 12V (=Von), I would expect RH around 60kOhm.

But my calculation is far apart from expected value:

From

RH = 1 / { [ (1/RL) + (1/333) / (Von-1) ] - [ 1/4500 ] }

I get 16,703 Ohms with Von=12 and RL=10k:

1 / { [(1/10000) + (1/333) / (12-1)] - [1/4500] } = 16,703

Very obviously my calculation is wrong, but why? Please advise, thank you.

NOTE: This question and answer originated from a customer support case which was handled by us. We regularly review support cases and add any helpful ones here for all to benefit from.

[Central SUPPORT · Accepted solution]

In mentioned equation you have to enter resistor values in kOhm (not in Ohm), see note below “Equation 1�? in datasheet: 

In your calculation if you remove last “000�? for RL value you will get RH around 109k for RL = 10k. Please verify.

Sorry for confusing formula in datasheet.