1-7. Example of Application of the Power-Down Protection Function (Partial Power-Down)

Partial power-down is possible if an IC with a power-down protection function is used.

To reduce power consumption, a system with two voltage domains (V_CC1 and V_CC2) might provide partial power-down mode in which the subsystem operating from V_CC1 is shut down. Suppose, for example, that the 74VHC Series is used in the V_CC1 domain. The 74VHC Series has an unintended parasitic diode between the output and power supply. Therefore, when V_CC2 > V_CC1, this parasitic diode turns on. In this case, the IC might be destroyed by the resulting large current. Device destruction can be prevented by using an IC with neither an input nor output parasitic diode (e.g., 74VHCT, 74LCX, and 74VCX Series). These series provide power-down protection.