I2C Pull Up Resistor Range Calculator
Calculate the resistor window from entered sink-current, low-level voltage, bus capacitance and allowed 30–70% rise time.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Calculate the low-state sink-current lower bound and the RC 30–70% rise-time upper bound independently.
Rmin=(VDD−VOL)/IOL; Rmax=tr/(ln(7/3) Cbus)
Worked example
3.3 V, VOL 0.4 V and 3 mA give minimum 966.666667 Ω. A 200 pF bus and 300 ns rise allowance give maximum about 1770.33375 Ω.
Assumptions and input details
Supply must exceed VOL. All limits are entered rather than selected from a speed-mode table. A negative window indicates incompatible assumptions. Bus leakage, parallel pullups, distributed capacitance and complete protocol compliance are excluded.
References: TI: I2C bus pull-up resistor calculation
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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