MC74HC4351

The Channel Select and Enable control pins should be at V_CC or GND logic levels. V_CC being recognized as a logic high and GND being recognized as a logic low. In this example:

                                                                  V_CC = + 5 V = logic high
                                                                  GND = 0 V = logic low

The maximum analog voltage swings are determined by the supply voltages V_CC and V_EE. The positive peak analog
voltage should not exceed V_CC. Similarly, the negative peak analog voltage should not go below V_EE. In this example, the difference between V_CC and V_EE is ten volts. Therefore, using the configuration in Figure 16, a maximum analog signal of ten volts peaktopeak can be controlled. Unused analog inputs/outputs may be left floating (i.e., not connected). However, tying unused analog inputs and outputs to V_CC or GND through a low value resistor helps minimize crosstalk and feedthrough noise that may be picked up by an unused switch.

Although used here, balanced supplies are not a requirement. The only constraints on the power supplies are that:

                                            V_CC GND = 2 to 6 volts
                                            V_EE GND = 0 to 6 volts
                                            V_CC V_EE = 2 to 12 volts
                                                     and V_EE   GND

When voltage transients above V_CC and/or below V_EE are anticipated on the analog channels, external Germanium or Schottky diodes (D_x) are recommended as shown in Figure 17. These diodes should be able to absorb the maximum anticipated current surges during clipping.