Analog front-end device and imaging apparatus
The analog front-end device of the invention includes an analog-digital converter for generating digital data corresponding to an analog charge signal and a RAM for storing therein digital data generated by the analog-digital converter. A memory control section reads digital data stored in the RAM during the time period when the output of an image sensor is invalid, and outputs the digital data externally via the data output section.
1 . An analog front-end device for converting an analog charge signal to digital data and outputting the digital data, the analog charge signal being outputted from an image sensor for photoelectrically converting a light image of an object, the device comprising:
an analog-digital converter for generating digital data corresponding to the analog charge signal;
a memory for storing therein digital data generated by the analog-digital converter;
a memory control section for reading digital data stored in the memory during the time period when the output of the image sensor is invalid; and
a digital data output section for receiving digital data read from the memory and outputting the digital data externally.
2 . The device of claim 1 , wherein the memory has a capacity of storing therein digital data of at least one line, and
the memory control section is configured to write digital data generated by the analog digital converter into the memory during the time period when the output of the image sensor is valid and read digital data from the memory during a horizontal blanking period.
3 . The device of claim 1 , wherein the digital data output section is configured to output digital data read from the memory externally as parallel data, and fixes the electrical level of data output during the time period when the output of the image sensor is valid.
4 . The device of claim 1 , wherein the digital data output section has a differential amplifier, is configured to convert digital data read from the memory to serial data by low voltage differential signaling (LVDS) and output the serial data, and turns off a constant current source of the differential amplifier and sets the output level at fixed logic during the time period when the output of the image sensor is valid.
5 . The device of claim 1 , wherein the memory control section is configured to output an address for assessing the memory in the form of a gray code.
6 . The device of claim 1 , wherein the memory control section is configured to write the output of the analog-digital converter into the memory before start of the time period when the output of the image sensor is valid.
7 . The device of claim 1 , wherein in the digital data output section, the transfer rate is set so as to complete output of data within a horizontal blanking period.
8 . The device of claim 1 , wherein the memory control section reads digital data from the memory in reverse order starting from the final address.
9 . The device of claim 1 , wherein the memory is configured to permit write of data from outside.
10 . The device of claim 1 , wherein the digital data output section outputs data as packets and prefixes sync header data to the output data.
11 . The device of claim 1 , wherein the digital data output section outputs data as packets and also as discontinuous data in a handshake mode.
12 . An imaging apparatus comprising the analog front-end device of claim 1 .