Analog-digital converter using current controlled voltage reference
AssigneeExar Corporation
InventorsJohn M. Caruso, Quoi V. Huynh, Roger A. Levinson
Life of this patent
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Abstract
A current driven span voltage source for use in an analog to digital converter includes a zero reference resistor serially connected with a resistor ladder. A first current source selectively passes a part of a first current through the resistor ladder to establish a span (gain) voltage range, and a second current source selectively passes a part of a second current through the zero reference resistor to establish a zero reference voltage for the span voltage range. The controlled current sources increase speed, reduce power and thermal noise, and improve temperature related performance as compared with voltage driven span and reference sources using operational amplifiers.
Claims21
An analog to digital converter (ADC) for receiving and converting an analog signal to a digital output comprising
- a code converter,
- a resistor ladder connected between a zero reference voltage and a maximum span voltage for use in comparing an analog voltage and driving said code converter,
- a first current driver means for selectively steering part of a first current through said resistor ladder and establishing said span voltage,
- a zero reference resistor serially connected with said resistor ladder, and
- a second current driver means for selectively steering a part of a second current through said zero reference resistor for establishing a zero reference voltage for said span voltage.
For use in an analog to digital converter (ADC), a current driven span voltage generator comprising
- a resistor ladder connected between a zero reference voltage and a maximum span voltage,
- a first current driver means for selectively steering part of a first current through said resistor ladder and establishing said span voltage,
- a zero reference resistor serially connected with said resistor ladder, and
- a second current driver means for selectively steering part of a second current through said zero reference resistor for establishing a zero reference voltage for said span voltage.
Dependencies are inferred from the claim text.