DIMM memory module reference voltage switching circuit
A non-volatile memory module includes a volatile memory circuit and a reference voltage generator coupled to supply a reference voltage to the volatile memory circuit. The reference voltage provides a level by which the volatile memory and external devices may communicate reliably at high speeds. The reference voltage is applied to an external interface of the non-volatile memory module through an isolation circuit. A control circuit coupled to the isolation interface and to a circuit which is adapted to detect when the non-volatile memory module no longer draws power from an external source.
1. A. non-volatile memory module comprising:
a volatile memory circuit;
a reference voltage generator coupled to supply a reference voltage to the volatile memory circuit;
the reference voltage provides a level by which the volatile memory circuit and external devices may communicate reliably at high speeds;
an isolation circuit through which the reference voltage is applied to an external interface of the non-volatile memory module; and
a control circuit coupled to the isolation interface and to a circuit which is adapted to detect when the non-volatile memory module no longer draws power from an external source and to operate the isolation circuit to isolate the reference voltage generator from the external interface when the non-volatile memory module no longer draws power from the external source.
2. A method comprising:
a memory module drawing power from an external source;
the volatile memory module providing a reference voltage from an internal source to both internal memory circuits and to an external system comprising the external source of power;
the memory module ceasing to draw power from the external source;
the act of ceasing to draw power from the external source causing the memory module to isolate the reference voltage from the external system while continuing to provide the reference voltage to the internal memory circuits.