VV5404 Datasheet, PDF (8/54 Pages) List of Unclassifed Manufacturers – CIF FORMAT DIGITAL IMAGE SENSOR

VV5404 & VV6404
3. Exposure Control
The exposure time for a pixel and the gain of the input amplifier to the 8-bit ADC are programmable via the serial
interface. The explanation below assumes that the gain and exposure values are updated together as part of a 5 byte
serial interface auto-increment sequence.
The exposure is divided into 2 components - coarse and fine. The coarse exposure value sets the number of lines a
pixel exposes for, while the fine exposure sets the number of additional pixel clock cycles a pixel integrates for. The
sum of the two gives the overall exposure time for the pixel array.
30 fps mode: Exposure Time = (Clock Divisor) x (Coarse x 393 + Fine) x (CKI clock period)/
25 fps mode: Exposure Time = (Clock Divisor) x (Coarse x 471 + Fine) x (CKI clock period)
Value
Units
30 fps mode
Min.
Max.
25 fps mode
Min.
Max.
Coarse
Video Lines
0
302
0
302
Fine
Pixel Clocks
0
356
0
434
Table 3 : Coarse and Fine Exposure Ranges.
If an exposure value is loaded outwith the valid ranges listed in the above table the value is clipped to lie within the
above ranges.
Gain Code, G[2:0]
Amplifier Gain
0
0
0
1
0
0
1
2
0
1
1
4
1
1
1
8
Table 4 : Main Gain Steps.
Exposure and gain values are re-timed within the sensor to ensure that a new set of values is only applied to the
sensor array at the start of each frame. Bit 0 of the Status Register is set high when a new exposure value is written
via the serial interface but has not yet been applied to the sensor array.
There is a 1 frame latency between a new exposure value being applied to the sensor array and the results of the
new exposure value being read-out. The same latency does not exist for the gain value. To ensure that the new
exposure and gain values are aligned up correctly the sensor delays the application of the new gain value by one
frame relative to the application of the new exposure value.
To eliminate the possibility of the sensor array seeing only part of the new exposure and gain setting, if the serial
interface communications extends over a frame boundary, the internal re-timing of exposure and gain data is disabled
while writing data to any location in the Exposure page of the serial interface register map. Thus if the 5 bytes of
exposure and gain data is sent as an auto-increment sequence, it is not possible for the sensor to consume only part
of the new exposure and gain data.
CD5404-6404F-A
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