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US 6,611,918 B1Granted
Method and apparatus for changing bias levels to reduce CMOS leakage of a real time clock when switching to a battery mode of operation
AssigneeIntel Corporation
InventorLawrence S. Uzelac
Life of this patent
Estimating the term…
Abstract
A CMOS circuit for low leakage battery operation connects the real time clock to the power supply when available or to a low leakage source when the power supply is not available.
Claims18
A leakage prevention device for a real time clock system, comprising:
- a real time clock circuit, having separated first and second power supply connections, and maintaining a count indicative of real time;
- and
- an associated circuit, which operates in a first mode when a power supply voltage is present and operates in a second mode when battery power is present, said second mode providing a biasing condition that minimizes leakage current during battery operation by changing source voltage levels for the real time clock circuit.
A method of operating a real time clock in a personal computer, comprising:
- operating a real time clock from a power supply during a first mode of operation;
- and
- operating said real time clock from a battery during a second mode of operation, said operating comprising setting a bias level which minimizes leakage current during said operating by changing source voltage levels for said real time clock.
A real time clock system, comprising:
- a real time clock circuit, having a first power supply connection;
- a controlling circuit for said real time clock circuit, said controlling circuit including a connection to a power supply and a connection to a battery and including a control circuit which connects said real time clock to said power supply connection when said power supply voltage is available, and connects said real time clock to a low leakage bias source to change source voltage levels for said real time clock circuit when said power supply is not available.
A real time clock system, comprising:
- a real time clock circuit, having a first power supply connection and a second power supply connection;
- a controlling circuit for said real time clock circuit, said controlling circuit connected between a power supply and said first power supply connection, and connected between a battery and said second power supply connection, and including a control circuit which detects if said power supply is available, connects said real time clock to said power supply connection when said power supply voltage is available, and if said power supply is not available, connects said battery to a bias network to produce a plurality of bias levels which reduce leakage currents by changing source voltage levels for said real time clock circuit, and connects said real time clock to said bias levels.
Dependencies are inferred from the claim text.