A non-volatile semiconductor memory device, which comprises (i) an interface having an input for receiving an input clock and a set of data lines for receiving commands issued by a controller including an erase command; (ii) a module having circuit components in a feedback loop configuration and being driven by a reference clock; (iii) a clock control circuit capable of controllably switching between a first state in which the reference clock tracks the input clock and a second state in which the reference clock is decoupled from the input clock; and (iv) a command processing unit configured to recognize the commands and to cause the clock control circuit to switch from the first state to the second state in response to recognizing the erase command. The module consumes less power when the reference clock is decoupled from the input clock than when the reference clock tracks the input clock.