Programmable logic device with partial battery backup
First Claim
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1. A PLD comprising:
- a logic portion powered by an external power supply;
a plurality of memory registers; and
a switching structure comprising a voltage level shift circuit for switching between connecting a battery pad to the plurality of memory registers and connecting the external power supply to the plurality of memory registers.
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Abstract
A PLD can be manufactured to include power supply lines from two sources so that a portion of the PLD can be backed up with a battery when power to the PLD is removed. A switch that supplies power to the backed up portion of the PLD receives power from both an external power supply and from the battery, and detects voltage level of the external power supply, switching to battery power when voltage from the external power supply is not sufficient.
107 Citations
6 Claims
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1. A PLD comprising:
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a logic portion powered by an external power supply;
a plurality of memory registers; and
a switching structure comprising a voltage level shift circuit for switching between connecting a battery pad to the plurality of memory registers and connecting the external power supply to the plurality of memory registers. - View Dependent Claims (2, 3, 4, 5, 6)
a detection circuit for detecting when the external power supply is providing a sufficient voltage; and
a pull-down device controlled from the battery pad to allow only the battery pad to be connected to an output terminal when the external power supply is not providing a sufficient voltage.
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Specification