Ultrasonic fingerprint sensor

1. A method of transferring data of an ultrasonic fingerprint sensor comprising:

an array of ultrasonic transducers,

one microcontroller unit (MCU),

a plurality of parallel mixed-signal Application-Specific Integrated Circuits (ASIC) each communicatively connected with the MCU and comprising a respective a data storage, and

for each of the mixed-signal ASICs, a plurality of parallel front-end ASICs, each communicatively connected with said mixed-signal ASIC and controlling a respective group of the transducers;

the method comprising, in at least one of the mixed-signal ASICs:

during a time period while a fingerprint is being captured by the fingerprint sensor, receiving analogue signals of the transducers from at least one of its connected front-end ASICs;

converting the analogue signals to digital data;

storing the digital data in its data storage;

obtaining an indication that the fingerprint is no longer being captured; and

sending the digital data via the MCU to processing circuitry of a host.

2. The method of claim 1 , wherein the digital data is sent at a rate of at least 1 Mbyte/s.

3. The method of claim 1 , wherein the time period while the fingerprint is being captured is within the range of 15-80 ms.

4. A non-transitory computer-readable storage medium comprising computer-executable instructions stored thereon for causing an ultrasonic fingerprint sensor to perform the method of claim 1 when the computer-executable instructions are executed by processing circuitry associated with the sensor.

5. An ultrasonic fingerprint sensor comprising:

an array of ultrasonic transducers;

one microcontroller unit (MCU) configured for obtaining a configuration of the transducers;

a plurality of parallel mixed-signal Application-Specific Integrated Circuits (ASIC) each configured to be communicatively connected with the MCU and for Analogue-Digital (AD) conversion of analogue signals from the transducers to digital data and comprising a respective data storage for storing said digital data; and

for each of the mixed-signal ASICs, a plurality of parallel front-end ASICs, each configured to be communicatively connected with said mixed-signal ASIC and for controlling a respective group of the transducers in accordance with the obtained configuration.

6. The sensor of claim 5 , wherein the array of ultrasonic transducers is a one-dimensional array.

7. The sensor of claim 5 , wherein the plurality of mixed-signal ASICs is within the range of 2-4 mixed-signal ASICs.

8. The sensor of claim 5 , wherein the plurality of front-end ASICs is within the range of 2-8 front-end ASICs for each of the mixed-signal ASICs.

9. The sensor of claim 5 , wherein the plurality of mixed-signal ASICs are configured to be communicatively connected with the MCU by means of a plurality of serial buses.

10. The sensor of claim 9 , wherein the plurality of mixed-signal ASICs are configured to be communicatively connected with the MCU by means of a respective serial bus of each of the plurality of mixed-signal ASICs.

11. An electronic device comprising:

host processing circuitry;

a screen comprising a display and a cover covering said display; and

the ultrasonic fingerprint sensor of claim 5 comprising a one-dimensional array of ultrasonic transducers peripherally arranged along at least one side of the screen, beside the display and below the cover;

wherein the MCU is configured to be communicatively connected with the host processing circuitry.

12. The device of claim 11 , wherein each of the mixed-signal ASICs is configured to store the digital data in its data storage during a time period while a fingerprint is being captured by the fingerprint sensor, and to transfer the stored digital data to the host processing circuitry after said time period when the fingerprint is no longer being captured.

13. The device of claim 12 , wherein the MCU has a Serial Peripheral Interface (SPI) having a clock frequency of at least 10 MHz, e.g. at least 15 MHz or at least 20 MHz.