Battery backed memory with low battery voltage trip, disconnect and lockout
First Claim
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1. A memory system having power backup comprising:
- a backup supply line receiving a backup voltage when a line voltage is lost;
an electronically controlled switch;
volatile memory receiving voltage from the backup supply line controlled by the electronically controlled switch, the memory providing a low power operating mode controlled by volatile data held in the memory;
a voltage supervisory circuit communicating with the backup supply line, the volatile memory, and the electronically controlled switch to operate the electronically controlled switch in response to a predetermined level in backup voltage below a normal backup voltage to disconnect the backup supply line from the volatile memory; and
further including a latching means connected between the voltage supervisory circuit and the electronically controlled switch whereby the electronically controlled switch is latched to disconnect the backup supply line from the volatile memory even after restoration of backup voltage to the normal backup voltage while the memory system is not receiving line voltage.
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Abstract
A memory system having power backup having memory circuits that may be set to a low power mode by means of volatile control registers, disconnects the memory circuits from the battery when low voltage conditions are detected so as to prevent reversion of the memory circuits to high current consumption modes such as would drain batteries after replacement.
26 Citations
17 Claims
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1. A memory system having power backup comprising:
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a backup supply line receiving a backup voltage when a line voltage is lost;
an electronically controlled switch;
volatile memory receiving voltage from the backup supply line controlled by the electronically controlled switch, the memory providing a low power operating mode controlled by volatile data held in the memory;
a voltage supervisory circuit communicating with the backup supply line, the volatile memory, and the electronically controlled switch to operate the electronically controlled switch in response to a predetermined level in backup voltage below a normal backup voltage to disconnect the backup supply line from the volatile memory; and
further including a latching means connected between the voltage supervisory circuit and the electronically controlled switch whereby the electronically controlled switch is latched to disconnect the backup supply line from the volatile memory even after restoration of backup voltage to the normal backup voltage while the memory system is not receiving line voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of operating a memory system having a backup supply line providing backup voltage when a line voltage is lost, the memory system having an electronically controlled switch, a volatile memory receiving backup voltage from the backup supply line controlled by the electronically controlled switch, the volatile memory providing a low power operating mode controlled by volatile data held in the volatile memory;
- the method comprising the steps of;
(a) monitoring the voltage of the backup supply line;
(b) in response to a predetermined level in backup voltage below a normal backup voltage, disconnecting the backup supply line from the volatile memory using the electronically controlled switch; and
(c) latching a signal controlling the electronically controlled switch thereby disconnecting the backup supply line from the volatile memory even after restoration of backup voltage to the normal backup voltage. - View Dependent Claims (12, 13, 14, 15, 16, 17)
- the method comprising the steps of;
Specification