Level Shifting

Level Shifting

Communication Protocols Technique

This technique will work with any GreenPAK that has dual voltage rails, such as the SLG46826V.

Often in a system-level design it’s necessary to combine the data from two signals that operate at different voltage levels. For example, the analog rails in a system might operate at 5.0V while the digital rails operate at 3.3V.

Many GreenPAK ICs solve this problem by using dual voltage rails: signals that operate at different rails can be input into the GreenPAK, manipulated, then output from the GreenPAK at either of the voltage rail levels.

When starting a new GreenPAK Designer design using a dual rail part you’ll be asked to input the voltage range of both rails (Figure 21). The available ranges of both rails will vary from part-to-part. The higher voltage rail should be designated as VDD, not VDD2.

Figure 21 Dual Rail Project Info

In dual rail parts the GPIO connections to the first and second rails are indicated by the color of the IO PIN within GreenPAK Designer (Figure 22). VDD will be indicated by blue pins and VDD2 will be indicated by amber pins. Once inside the GreenPAK matrix the signals from the different voltage levels will behave identically.

Figure 22 Dual Rail Logic Example

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