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Non-volatile memory module

  • US 5,798,961 A
  • Filed: 08/23/1994
  • Issued: 08/25/1998
  • Est. Priority Date: 08/23/1994
  • Status: Expired due to Term
First Claim
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1. A non-volatile memory module for use in a system having a predetermined system voltage comprising:

  • a mounting substrate having an input port and an output port;

    a memory array including at least one volatile memory mounted on the mounting substrate, said volatile memory having a power input terminal for coupling power to said volatile memory in normal operation;

    a rechargeable battery mounted on the mounting substrate, said rechargeable battery having first and second connections;

    a switch circuit mounted on said mounting substrate and having an input terminal coupled to said rechargeable battery, an output terminal coupled to the power input terminal and a control terminal operative to cause said switch to assume one of a high impedance and a low impedance state in response to a control signal;

    a charging circuit mounted on the mounting substrate, said charging circuit having a charging circuit output coupled to said first battery connection and a charging circuit input for coupling to said predetermined system voltage;

    a system voltage monitoring circuit having a first port coupled to said input port of the mounting substrate and having an output port coupled to the control terminal of said switch circuit, wherein said system voltage monitoring circuit activates the control terminal of said switch in response to the predetermined system voltage reaching a predetermined threshold voltage;

    a battery voltage monitor circuit disposed on said mounting substrate, said battery voltage monitor circuit having an input port coupled to said first battery connection and having an output port coupled to said output port of said mounting substrate, said battery voltage monitor circuit being operative to provide a warning signal at said output port when the voltage at said first battery connection drops below a predetermined value,wherein said rechargeable battery includes one of a lithium cell and a nickel cadmium cell and said memory array includes one of a dynamic random access memory array and a pseudo-static random access memory array; and

    a battery temperature monitor circuit disposed on said memory module and coupled to said charging circuit, said battery temperature monitor circuit being operative to produce an output voltage indicative of the ambient temperature, said battery temperature monitoring circuit having a voltage threshold and being operative to permit charging of said rechargeable battery only if the battery temperature monitoring circuit output voltage is below said voltage threshold.

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