AN883 Datasheet, PDF (3/4 Pages) Silicon Laboratories – LOW-COST IC LEVEL TRANSLATOR

AN883
Figure 3. SDA Line at 200 mV per Division
When the 3.3 V side (blue line) goes all the way low, the 1.8 V side (yellow line) goes to about 350 mV, which is the
Schottky diode drop. When the 1.8 V side (yellow line) goes all the way low, the 3.3 V side goes to about 150 mV,
which is the saturation voltage of the transistor.
4. Conclusion
The low-cost translator circuit allows translation from higher voltages, such as 3.3 or 5 V, to lower voltages, such
as 1.8 or 3.3 V. For the case where SCL is unidirectional, only 2 diodes, 3 resistors, and one transistor are needed.
In high volume manufacture, the cost of these components would be well under $0.05.
Rev 0.1
3