QDJD-J821-SCR00 Datasheet, PDF (1/15 Pages) AVAGO TECHNOLOGIES LIMITED – Robust CMOS-Schmitt input

QDJD-J821-SCR00
Color Management System Feedback Controller
Data Sheet
Description
The QDJD-J821 is a CMOS mixed-signal IC designed to
be the optical feedback controller of an LED-based light-
ing system. A typical system consists of an array of red,
green and blue LEDs, LED drivers, a tri-color photosensor
that samples the light output and the QDJD-J821. The IC
interfaces directly to the photosensor, processes the color
information and adjusts the light output from the LEDs
until the desired color is achieved. To achieve this, the IC
integrates a high-accuracy 10-bit analog-to-digital con-
verter front-end, a color data processing logic core and a
high-resolution 12-bit PWM output generator.
By employing a feedback system and the QDJD-J821,
the light output produced by the LED array maintains its
color over time and temperature. In addition, the desired
color can be specified using a standard CIE color space.
In addition, by incorporating a standard I2C serial inter-
face, specifying the color of the LED array’s light output
is as simple as picking the color coordinates from the
CIE color space and writing several bytes of data to the
device.
The output PWM signals are connected directly to the
LED drivers as enable signals. The PWM signals control
the on-time duration of the red, green and blue LEDs.
That duration is continually adjusted in real-time to
match the light output from the LED array to the speci-
fied, desired color.
Features
• -40 to 125°C operation
• I²C Serial Interface
• Robust CMOS-Schmitt input
• CMOS/TTL compatible output
• Multiple color input formats
– CIE XYZ, Yxy, Yu’v’ and RGB
• 3-channel analog interface to color sensor
– X, Y and Z channels
• 3-channel 12-bit PWM output
– Red, Green and Blue LED channels
• Internal computation of calibration data
• Internal clock generator
• Internal reference voltage generator
• Error flag output
• External push-button interface
• Only passive components required externally
Applications
• Backlighting
• General illumination
• Mood / accent lighting
• Color context sensitive appliances
ESD WARNING: Standard CMOS handling precautions should be observed to avoid static discharge.