An optical biometric sensor comprising: a global shutter image sensor comprising an array of photodetectors ; a read-out circuitry controllable for converting analog sensing signals to digital signals, the analog sensing signals being indicative of an image acquired by the global shutter image sensor ; a memory configured to store digital data originating from only a subset of photodetectors in the array of photodetectors, and a timing circuitry configured to control start and stop of analog to digital conversion of the analog sensing signals resulting from a simultaneous exposure of the entire array of photodetectors, the analog to digital conversion is performed by the read-out circuitry such that when the analogue sensing signals originating from a subset of photodetectors in the array of photodetectors has been converted and stored on the memory , analog to digital conversion of the analog signals from a next subset of photodetectors in the array of photodetectors is initiated, the conversion of the analog data of a next subset of photodetectors in the array of photodetectors is completed before all digital data from the prior subset of photodetectors in the array of photodetectors has been read from the memory to a data transfer bus , such that a data production rate of digital signals resulting from the converted analog sensing signals from the simultaneous exposure of the entire array of photodetectors is below or equal to a present data transfer capacity on the data transfer bus configured to transfer the digital data indicative of the digital signals from the memory of the optical biometric sensor to a host device as the digital data is produced. a global shutter image sensor comprising an array of photodetectors ; a read-out circuitry controllable for converting analog sensing signals to digital signals, the analog sensing signals being indicative of an image acquired by the global shutter image sensor ; a memory configured to store digital data originating from only a subset of photodetectors in the array of photodetectors, and a timing circuitry configured to control start and stop of analog to digital conversion of the analog sensing signals resulting from a simultaneous exposure of the entire array of photodetectors, the analog to digital conversion is performed by the read-out circuitry such that when the analogue sensing signals originating from a subset of photodetectors in the array of photodetectors has been converted and stored on the memory , analog to digital conversion of the analog signals from a next subset of photodetectors in the array of photodetectors is initiated, the conversion of the analog data of a next subset of photodetectors in the array of photodetectors is completed before all digital data from the prior subset of photodetectors in the array of photodetectors has been read from the memory to a data transfer bus , such that a data production rate of digital signals resulting from the converted analog sensing signals from the simultaneous exposure of the entire array of photodetectors is below or equal to a present data transfer capacity on the data transfer bus configured to transfer the digital data indicative of the digital signals from the memory of the optical biometric sensor to a host device as the digital data is produced. <EOS>