PYTHON25K Datasheet, PDF (27/87 Pages) ON Semiconductor – PYTHON 25K/16K/12K/10K Global Shutter CMOS Image Sensors

NOIP1SN025KA, NOIP1SN016KA, NOIP1SN012KA, NOIP1SN010KA
IMAGE SENSOR TIMING AND READOUT
Global Shutter Mode
Pipelined Global Mode (Master)
The sensor timing in master global shutter mode is
controlled by the user by means of configuration registers.
One can distinguish three parameters for the frame timing in
global shutter mode:
• Image Array Reset Length
• Integration Time
• Frame Length
The relation between these parameters is:
Frame Length = Reset Length + Integration Time
The FOT time needs to be added to the frame length
parameter to determine the total frame Time
Total Frame Time = FOT Time + Frame Length
Frame and integration time configuration can be controlled
in two ways:
1. fr_mode = 0x0
The reset length and integration time is configured
by the user. The sensor shall calculate the frame
length as the sum of both parameters.
2. fr_mode = 0x1
The frame length and integration time is
configured by the user. The reset time during
which the pixels are reset, is calculated by the
sensor as being the difference between the frame
length and the desired integration time.
The configuration registers are exposure[15:0] and
fr_length[15:0]. The latter configuration register is either
used as Reset Length configuration (fr_mode = 0x0) or as
Frame Length (fr_mode = 0x1). The granularity of both
registers is defined by the mult_timer[15:0] register and is
expressed in number of 72 MHz cycles (13.889 ns nominal).
Reset Length and Integration Time as Parameters
The reset time for the pixel array is controlled by the
registers fr_length[15:0] and exposure[15:0]. The
mult_timer configuration defines the granularity of the
registers fr_length and exposure and is to be read as the
number of 72 MHz cycles (13.889 ns nominal).
The exposure control for pipelined global master mode is
depicted in Figure 22.
The pixel values are transferred to the storage node during
the FOT, after which all photo diodes are reset. The reset
state remains active for a certain time, defined by the
fr_length and mult_timer registers, as shown in the figure.
Meanwhile, the image array is read out line by line. After
this reset period, the global photodiode reset condition is
abandoned. This indicates the start of the integration or
exposure time. The length of the exposure time is defined by
the registers exposure and mult_timer.
NOTES:
• The start of the exposure time is synchronized to the
start of a new line (during ROT) if the exposure period
starts during a frame readout. Therefore, the effective
time during which the image core is in a reset state is
extended to the start of a new line.
• Make sure that the sum of the reset time and exposure
time exceeds the time required to read out all lines. If
this is not the case, the exposure time is extended until
all (active) lines are read out.
Frame Length and Integration Time as Parameters
When fr_mode is configured to 0x1, one configures the
frame time and exposure. The reset_length is determined by
the sequencer. This configuration mode is depicted in
Figure 2.
The frame length is configured in register fr_length, while
the integration time is configured in register exposure. The
mult_timer register defines granularity of both settings.
Note that the FOT needs to be added to the configured
fr_length to calculate the total frame time.
Triggered Global Shutter (Master)
In master triggered global mode, the start of integration
time is controlled by a rising edge on the trigger pin. The
exposure or integration time is defined by the registers
exposure and mult_timer, similar to the master pipelined
global mode. The fr_length configuration is not used. This
operation is graphically shown in Figure 24.
NOTES:
• The falling edge on the trigger pin does not have any
impact. However, the trigger must be asserted for at
least 100 ns.
• The start of the exposure time is synchronized to the
start of a new line (during ROT) if the exposure period
starts during a frame readout. Therefore, the effective
time during which the image core is in reset state is
extended to the start of a new line.
• The trigger pin needs to be kept low during the FOT.
The monitor pins can be used as a feedback to the
FPGA/controller (eg. use monitor0, indicating the very
first line when monitor_select = 0x5 − a new trigger can
be initiated after a rising edge on monitor0).
If the exposure timer expires before the end of readout, the
exposure time is extended until the end of the last active line.
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