Analogue-to-digital converter
AssigneeNordic Semiconductor ASA
InventorsCarsten Wulff, Ola Bruset, Werner Luzi
Life of this patent
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Abstract
An integrated-circuit, continuous-time, sigma-delta analogue-to-digital converter has a single-ended analogue input, a converter reference input, and a ground connection. The converter has a resistor-capacitor integrator arranged to receive the single-ended analogue input. The integrator comprises a differential amplifier. The converter also has a clocked comparator connected to an output from the integrator, and circuitry arranged so that reference inputs to the amplifier and to the comparator can be maintained at a common voltage derived from the converter reference input.
Claims31
An integrated-circuit, continuous-time, sigma-delta analogue-to-digital converter having a single-ended analogue input, a converter reference input, and a ground connection, wherein the converter comprises:
- a resistor-capacitor integrator arranged to receive the single-ended analogue input, wherein the integrator comprises a differential amplifier having an amplifier reference input;
- a clocked comparator arranged to receive an output from the integrator and having a comparator reference input;
- and
- circuitry arranged so that the amplifier reference input and the comparator reference input can be maintained at a common voltage derived from the converter reference input.
An analogue-to-digital converter as claimed in any preceding claim, wherein said circuitry comprises a voltage divider between the converter reference input and ground, the output of which is connected to the amplifier reference input and to the comparator reference input.
An analogue-to-digital converter as claimed in any preceding claim, wherein the amplifier reference input is a non-inverting input to the differential amplifier.
An analogue-to-digital converter as claimed in any preceding claim, wherein the differential amplifier is an operational transconductance amplifier.
An analogue-to-digital converter as claimed in any preceding claim, wherein the converter comprises circuitry arranged so that, in use, the current flowing into a second input to the amplifier depends on:
- (i) the voltage at the single-ended analogue input, (ii) the converter reference voltage, and (iii) the output state of the clocked comparator.
An analogue-to-digital converter as claimed in any preceding claim, further comprising a clock input, wherein the comparator is configured to use the clock input to define an integration step.
An analogue-to-digital converter as claimed in any preceding claim, wherein said circuitry comprises means arranged to switch the voltage at a point in the circuitry between two values in dependence on the binary output of the comparator.
An analogue-to-digital converter as claimed in any preceding claim, wherein said circuitry comprises an arrangement of first, second and third resistors, wherein a first end of the first resistor is connected to the single-ended analogue input, a first end of the second resistor is connected to ground, and a first end of the third resistor is switchably connectable to the converter reference input or to ground.
An analogue-to-digital converter as claimed in any preceding claim, comprising a counter arranged to receive the binary output of the comparator.
An analogue-to-digital converter as claimed in any preceding claim, wherein the converter is an incremental converter.
An integrated-circuit, continuous-time, sigma-delta analogue-to-digital converter having a single-ended analogue input, a converter reference input, and a ground connection, wherein the converter comprises an input resistor having a first end connected to the single-ended analogue input, and an offset resistor having a first end connected to ground, wherein the second ends of the input and offset resistors are connected to an input to a differential amplifier in an RC integrator circuit, wherein the input to the differential amplifier is also selectably connectable through a reference resistor to either the converter reference input or to ground, and wherein the gain of the converter is determined as a function of the ratio of the input resistor value to the reference resistor value and of the ratio of the offset resistor value to the reference resistor value.
Dependencies are inferred from the claim text.