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US 2003/0189862 A1Published application
Backup memory control unit with
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsChikara Yokoyama, Kyoji Higasa, Kazuyoshi Ohtsuka
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Abstract
A backup memory control unit can reduce the current consumption when a memory (SDRAM) is inactive by providing the memory with an unsettled mode in which no power is supplied to the memory. It provides the memory with the unsettled mode, and halts the power supply from a backup power supply to the SDRAM in the unsettled mode in which the SDRAM is not in operation, thereby limiting an increase in the current consumption. The functions are executed by a hardware circuit without using a backup microcomputer.
Claims6
A backup memory control unit comprising:
- a memory circuit having an unsettled mode in which no power is supplied, a normal operation mode and a self-refresh mode, said memory circuit being a volatile memory;
- a main power supply for supplying said memory circuit with main power;
- a backup power supply for supplying said memory circuit with backup power;
- a voltage detecting circuit for detecting a state of a supply voltage fed by said main power supply and said backup power supply;
- a power supply switching circuit for switching power supply to said memory circuit between said main power supply and said backup power supply;
- and
- control means for controlling said power supply switching circuit in response to the supply voltage detected by said voltage detecting circuit, and for halting the power supply to said memory circuit in the unsettled mode.
4 more elements
Dependencies are inferred from the claim text.