LED Backlight with I2C Programmable Brightness Controller and LCD Bias Voltage Supply
Controller operates from a 12VDC supply and provides brightness and contrast control for an LCD display with LED backlight.
The Ringdale 05-15860000 controller operates from a 12VDC supply and provides brightness and contrast control for an LCD display with LED backlight. An SPI interface accepts microcontroller signals to adjust the brightness and contrast levels.
• Retrofitting LCD display with LED backlighting
• Other LED lighting applications
The Ringdale 05-15860000 controller operates from a 12VDC supply. A 3-24mA adjustable output drives a string of LEDs. A 26-33V adjustable output provides a contrast control signal for an LCD display. The outputs are controlled by a 3.3V/5V SPI interface.
11 to 15VDC is supplied to terminal J4. The input is reverse-voltage protected. The controller will power up with a default 13.5mA supplied to the LED string and 29.2V supplied to the contrast control output.
The two outputs may be adjusted through the SPI interface by communicating with a dual digital pot internal to the controller. The LED output will interface directly with the Ringdale 05-15880000 LED backlighting strip. The SPI can operate at either 3.3V or 5.0V (jumper selectable). The SPI interface is 4-pin connector J3.
The 05-15860000 controller has 4 connectors for connecting the supply, SPI interface, and the two outputs.
Power Supply – J4
11 to 15VDC is connected to J4. J4 accepts a plug-in 2-terminal strip, Kobiconn P025ESDVP-E. Pin 1 is +V and Pin 2 is –V. The screw terminals accommodate 28 to 12 AWG stranded conductors. The power input is reverse-voltage protected.
SPI Interface – J3
J3 is a 4-pin 2mm pitch connector that accepts a Molex 35507-0400 plug with Molex 50210-8100 pins.
Pin 1: chip select
Pin 2: clock
Pin 3: signal in
Pin 4: signal out.
Either 3.3V or 5.0V signals may be used with the appropriate setting of jumper JP1.
LED output – J1
J1 is a 3-pin connector for connecting an LED string. The connector is a .100” pitch polarizing type with latch and mates with Molex 50-57-9403 using Molex 16-02-1125 pins. Pin 1 is the positive output from the controller board and Pin 3 is the negative return. Pin 2 is unconnected.
Contrast output – J2
J2 is a 2-pin connector for connecting the contrast voltage output. The connector is a .100” pitch polarizing type with latch and mates with Molex 50-57-9402 using Molex 16-02-1125 pins. Pin 1 is ground and Pin 2 is the positive output voltage.
The 4-wire SPI interface at J3 permits adjustment of the LED current and contrast voltage outputs from an external microcontroller. See the pinout in section 3.2. A 3.3V or 5.0V interface is selectable by Jumper JP1.
A command byte 0x11 causes the data byte to be written to potentiometer 0. A command byte 0x12 causes the data byte to be written to potentiometer 1. The data is loaded when CS returns high.
The signal out line from the dual digital pot is included in the SPI interface but is not required for normal operation.
The 3.625” X 1.5” PCB requires a minimum vertical clearance of 0.6”. Two 0.162” diameter mounting holes are provided.