Separate Digital Voltage Nodes

Systems can have multiple digital voltages that are similar in value which need to be separated for optimal performance. For example, an incoming 3.3-V signal may need to communicate with an internally regulated 3.3-V device, and the two may vary separately from 3 V to 3.6 V. In this case, true isolation is not required, however separation of the voltage nodes will prevent issues from the voltage mismatch.

Left: block diagram for open-drain buffer. Right: block diagram for push-pull buffer.

Figure 1-1 Separate Voltage Nodes Block Diagrams

Design Considerations

Input thresholds are referenced to the buffer's supply voltage
Output voltage for open-drain devices can be selected by changing the pull-up resistor supply connection
Output voltage for push-pull devices is equal to the buffer's supply voltage
For traces longer than 12 cm (4760 mil) see Drive Transmission Lines With Logic
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Recommended Parts

Part Number	AEC-Q100	V_CC Range	Channels	Features
SN74LVC1G34		1.65 V – 5.5 V	1	Over-voltage tolerant inputs Partial power down (Ioff) Balanced high-drive CMOS outputs (up to 32 mA)
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SN74LV244A-Q1	✓	2 V – 5.5 V	8
SN74LVC16244A		1.65 V – 3.6 V	16	Over-voltage tolerant inputs Partial power down (Ioff) Balanced high-drive CMOS outputs (up to 24 mA)
SN74LVC16244A-Q1	✓	1.65 V – 3.6 V	16

For more devices, browse through the online parametric tool where you can sort by desired voltage, channel numbers, and other features.