Storage device and operating method thereof

A storage device comprising:

• a current limiter configured to receive an external voltage and to limit current;
• at least one voltage regulator configured to receive the external voltage output from the current limiter, and to generate a first power supply voltage, a second power supply voltage, and a third power supply voltage;
• a voltage sensor configured to sense the external voltage;
• a NAND package configured to receive the first power supply voltage from the at least one voltage regulator, and including a plurality of NAND flash memory devices;
• a volatile memory device configured to receive the second power supply voltage from the at least one voltage regulator;
• and
• a controller configured to receive the third power supply voltage from the at least one voltage regulator and to control the NAND package and the volatile memory device, wherein:
• the controller receives a voltage information signal from the voltage sensor, and selects a data transfer mode, the data transfer mode being selected as either a normal mode or a brown-out mode in response to the voltage information signal;
• wherein the normal mode is selected when the external voltage exists within a normal range between a first operation voltage and a second operation voltage, and the brown-out mode is selected when the external voltage exists within a low power range below the normal range and between the second operation voltage and a power-off detection voltage;
• wherein the first operation voltage is a maximum operation voltage of the normal range and the second operation voltage is a minimum operation voltage of the normal range;
• wherein the storage device supports a nonvolatile memory device (NVM) buffer operation in both the normal mode and the brown-out mode;
• and
• wherein an operation speed of the brown-out mode is different from an operation speed of the normal mode.

An operating method of a storage device, the method comprising:

• monitoring an external voltage;
• determining whether the external voltage is lower than a minimum operation voltage;
• when the external voltage is lower than the minimum operation voltage, determining whether the external voltage is lower than a power-off detection voltage;
• performing an input/output operation according to a first brown-out mode when the external voltage is lower than the minimum operation voltage and higher than the power-off detection voltage;
• performing an input/output operation according to a normal mode when the external voltage is not lower than the minimum operation voltage;
• and
• dumping a firmware when the external voltage is lower than the power-off detection voltage, wherein the input/output operation according to the first brown-out mode includes a write through operation supported in both the normal mode and the brown-out mode, and wherein an operation speed of the brown-out mode is different from an operation speed of the normal mode.