Asynchronous successive approximation analog-to-digital converter and related methods and apparatus
An ultrasound device including an asynchronous successive approximation analog-to-digital converter and method are provided. The device includes at least one ultrasonic transducer, a plurality of asynchronous successive-approximation-register (SAR) analog-to-digital converters (ADC) coupled to the at least one ultrasonic transducer, at least one asynchronous SAR in the plurality having a sample and hold stage, a digital-to-analog converter (DAC), a comparator, and control circuitry, wherein a DAC update event following at least one bit conversion is synchronized to a corresponding DAC update event of at least one other ADC in the plurality of ADCs.
1. An apparatus, comprising:
an ultrasonic transducer;
a receive circuitry coupled to the ultrasonic transducer, the receive circuitry providing an analog signal to represent information relating to an ultrasound image;
an Analog-to-Digital Converter (ADC) to communicate with the receive circuitry, the ADC further comprising a Successive Approximation Register (SAR) Controller, the ADC configured to receive the analog signal, a first clock signal and a second clock signal and output a digital representation of the analog signal;
wherein:
the first clock signal and the second clock signal govern timing of successive analog-to-digital conversions;
the first and the second clock signals are independent of a high-speed clock signal;
the SAR Controller is configured to successively approximate a quantification value for one bit per clock cycle, proceeding from the most significant bit (MSB) to the least significant bit (LSB); and
conversion of the MSB is triggered by the second clock signal.
2. The apparatus of claim 1 , wherein the digital representation of the analog signal comprises a digital word of N bits, wherein N is between 5 and 20.
3. The apparatus of claim 1 , wherein conversion of subsequent bits of the SAR ADC is triggered by a signal subsequent to a previous conversion.
4. The apparatus of claim 1 , wherein the ultrasonic transducer is part of an array of M×N ultrasonic transducers.
5. A method to detect an ultrasound signal, comprising:
receiving a first plurality of ultrasound signals from a body, the first plurality of ultrasound signals defining an analog signal;
averaging the first plurality of ultrasound signals to obtain a first average signal; and
digitizing the first average signal at an Analog-to-Digital Converter (ADC) by successive approximation of a quantized representation of the first average signal by iteratively decreasing an error signal associated with the analog signal;
wherein the successive approximation of the quantized representation for at least one bit of data is an asynchronous successive approximation independent of a clock cycle; and
wherein at least one step of iteratively decreasing the error signal is triggered by completion of a prior iteration cycle.
6. The method of claim 5 , wherein a first conversion cycle of the successive approximation is triggered by a first clock cycle and a subsequent conversion cycle of the successive approximation is triggered by completion of the first conversion cycle.
7. The method of claim 5 , wherein the step of averaging the first plurality of ultrasound signals further comprises summing the first plurality of ultrasound signals to provide a summed analog signal.
8. The method of claim 7 , further comprising receiving and holding the summed analog signal for one clock cycle.
9. The method of claim 7 , further comprising converting a successive approximation word to an equivalent analog signal to produce a control for comparing against the summed analog signal.