MT9J003
www.onsemi.com
28
FEATURES
Scaler
The MT9J003 sensor includes scaling capabilities. This
allows the user to generate full field-of-view, low resolution
images. Scaling is advantageous because it uses all pixel
values to calculate the output image which helps to avoid
aliasing. It is also more convenient than binning because the
scale factor varies smoothly and the user is not limited to
certain ratios of size resolution.
The scaling factor is programmable in 1/16 steps.
ScaleFactor +
scale_n
scale_m
+
16
scale_m
(eq. 6)
♦ scale_n is fixed at 16.
♦ scale_m is adjustable with R0x0404
Legal values for m are 16 through 128. The user has
the ability to scale from 1:1 (m = 16) to 1:8
(m = 128).
Shading Correction
Lenses tend to produce images whose brightness is
significantly attenuated near the edges. There are also other
factors causing color plane nonuniformity in images
captured by image sensors. The cumulative result of all these
factors is known as image shading. The MT9J003 has an
embedded shading correction module that can be
programmed to counter the shading effects on each
individual Red, GreenB, GreenR, and Blue color signal.
The Correction Function
Color-dependent solutions are calibrated using the sensor,
lens system and an image of an evenly illuminated,
featureless gray calibration field. From the resulting image,
register values for the color correction function
(coefficients) can be derived.
The correction functions can then be applied to each pixel
value to equalize the response across the image as follows:
Pcorrected (row, col) + Psensor (row, col) f(row, col)
(eq. 7)
♦ where P are the pixel values and f is the color
dependent correction functions for each color
channel.
Each function includes a set of color-dependent
coefficients defined by registers R0x3600–3726. The
function’s origin is the center point of the function used in
the calculation of the coefficients. Using an origin near the
central point of symmetry of the sensor response provides
the best results. The center point of the function is
determined by ORIGIN_C (R0x3782) and ORIGIN_R
(R0x3784) and can be used to counter an offset in the system
lens from the center of the sensor array.
One-Time Programmable Memory
The MT9J003 has a two-byte OTP memory that can be
utilized during module manufacturing to store specific
information about the module. This feature provides system
integrators and module manufacturers the ability to label
and distinguish various module types based on lens, IR-cut
filter, or other properties.
During the programming process, a dedicated pin for high
voltage needs to be provided to perform the anti-fusing
operation. This voltage (V
PP) would need to be 8.5 V +3%.
Instantaneous V
PP cannot exceed 9 V at any time. The
completion of the programming process will be
communicated by a register through the two-wire serial
interface.
Because this programming pin needs to sustain a higher
voltage than other input/output pins, having a dedicated high
voltage pin (V
PP) minimizes the design risk. If the module
manufacturing process can probe the sensor at the die or
PCB level (that is, supply all the power rails, clocks,
two-wire serial interface signals), then this dedicated high
voltage pin does not need to be assigned to the module
connector pinout. However, if the V
PP pin needs to be
bonded out as a pin on the module, the trace for V
PP needs
to carry a maximum of 1mA is needed for programming
only. This pin should be left floating once the module is
integrated to a design. If the VPP pin does not need to be
bonded-out as a pin on the module, it should be left floating
inside the module.
The programming of the OTP memory requires the sensor
to be fully powered and remain in software standby with its
clock input applied. The information will be programmed
through the use of the two-wire serial interface, and once the
data is written to an internal register, the programming host
machine will apply a high voltage to the programming pin,
and send a program command to initiate the anti-fusing
process. After the sensor has finished programming the OTP
memory, a status bit will be set to indicate the end of the
programming cycle, and the host machine can poll the
setting of the status bit through the two-wire serial interface.
Only one programming cycle for the 16-bit word can be
performed.
Reading the OTP memory data requires the sensor to be
fully powered and operational with its clock input applied.
The data can be read through a register from the two-wire
serial interface.
The steps below describe the process to program and
verify the programmed data in the OTP memory:
1. Apply power to all the power rails of the sensor
(V
DD, VDD_IO, VAA, VAA_PIX, VDD_PLL, and
VDD_TX0).
z Set VAA to 3.1 V during OTP memory
programming phase.
z VPP needs to be floated during this phase.
z Other supplies at nominal.
2. Provide 24 MHz EXTCLK clock input. The PLL
settings are discussed at the end of the document.
3. Perform the proper reset sequence to the sensor.
4. Place the sensor in soft standby
(sensor default state upon power-up) or ensure the
