AN10579 | DigiCamel IC Datasheet

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Driving LED light bars using NXP solutions Rev. 01 — 1 February 2007 Application note Document information Info Content Keywords LED, LED controller, I2C, light bar, RGB, color mixing, architectural lighting, LED lighting, LED driver, PWM, STARplug+, SMPS, power conversion Abstract Description of Avago light bars, driving high brightness color LED strings for color mixing and lighting applications using NXP Semiconductors PCA9633 LED driver is discussed. An offline regulated power supply for the LEDs is also included.

AN10579_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 1 February 2007 2 of 16 Contact information For additional information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com NXP Semiconductors AN10579 Driving LED light bars using NXP solutions

Revision history

AN10579_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 1 February 2007 3 of 16 NXP Semiconductors AN10579 Driving LED light bars using NXP solutions 1. Introduction Light Emitting Diodes (LEDs) have been used in electronic systems for many years primarily as indicator lights on electronic devices. Recent advances in high brightness and color LEDs have made them suitable for a wide range of new applications. Today, LEDs are being used in applications in cell phones and media players for fun lighting to architectural/commercial lighting to replace conventional light sources. Key enablers driving penetration of LED lighting is the availability of high brightness LEDs and intelligent LED controllers. Product designers incorporating high brightness LEDs face many challenges. Among them, thermal management, driver scheme/topology, device matching for color balance and consistency. Manufactures and OEMs alike are starting to make available LED modules consisting of clusters or strings of many LEDs of different colors in single packages. One such product family is ADJD-MJ00/ADJD-MJ10 RGB light bars from Avago Technologies. This application note describes how NXP power solutions and intelligent LED controllers can be used to drive the LED light bars to provide programmable color mixing and brightness control features. 2. LED light bars Avago RGB LED Light Source ADJD-MJ00/ADJD-MJ10 is a high performance device that can be operated at high driving current. It comes with a plug-and-play electrical connector. The built-in heat sink and the mechanical mounting features simplify the thermal management of a lighting solution. This enables effective heat transfer and maintain LED junction below maximum allowed temperature. Red, Green and Blue colors premix in the reflector cavity to produce required color. The reflector cavity design maximizes the light extraction as well as the color mixing. Together with closely pitched LED dice, the color mixing is best of its class.

2.1 Electrical configuration

The light bar consists of four LED strings. Each LED string consists of ten LEDs connected in series, except for red which consist of 10 pairs of parallel connected LEDs. Each pair of parallel connected LEDs can be considered equivalent to a single large LED. That is, for RED color, between R+ and R− terminal, there is an equivalent of ten series-connected red LEDs. The LED strings are: Red color: Connect with R+ and R− terminals. Green color: Connect with G1+ and G1− terminals. Green color: Connect with G2+ and G2− terminals. Blue color: Connect with B+ and B− terminals. The circuit is shown in Figure 1.

2.2 Color configuration

The arrangement of Red, Green and Blue LEDs within the light bar is shown in Figure 2. The three colors in the LED light source will mix to form a resultant color. Depending on the mix ratio, any color within the color gamut of the LED can be obtained. The color gamut of the LED light source is the triangle formed by the three colors points on the CIE chromaticity chart. The three color points are from Red, Green and Blue LED color. Fig 1. Electrical configuration pin 1 G1+ pin 5 G1− pin 2 pin 6 pin 3 pin 7 pin 4 G2+ pin 8 G2− 002aac791 Fig 2. Color arrangement 002aac792 49 50484746454443424140393837363534333231302928272625242322212019181716151413121110987654321position BGRRGGBRRGGBRRGGBRRGGBRRGGBRRGGBRRGGBRRGGBRRGGRRBGcolor Fig 3. ADJD-MJ00, ADJD-MJ10 light bars

2.3 Drive configuration

Figure 4 shows a basic drive circuit for the light bar. A fixed voltage is applied to the positive terminal of each LED string through a resistor. The negative terminal is connected to GND. The value of the resistor is determined by the current needed and the input voltage, according to Equation 1: (1) The current required for red, green and blue color LEDs are determined from the required luminous intensity needed to obtain the color. The forward voltage drop, VF of the LED strings is determined from the IF /V F graphs in the specification. The resistor required can thus be calculated from Equation 1. To adjust the resultant color and the overall brightness of the light bar, the intensities of each string needs to be controllable. This can be accomplished by Pulse Width Modulated (PWM) power switches on each channel as shown in Figure 5. While the PWM control of LED strings can be implemented using a microcontroller or other hardware logic; using a PCA9633 is less complex, easier to implement and provides a simpler and flexible (scalable) design, especially, when multiple PWMs are involved. Fig 4. Basic drive circuit for light bar R VI VF– IF 002aac793 RR VI GND RB RG RG

AN10579_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 1 February 2007 6 of 16 NXP Semiconductors AN10579 Driving LED light bars using NXP solutions 3. The PCA9633 intelligent LED controller

3.1 Programmable RGGB/RGBA controller

The PCA9633 is an I2C-bus controlled 4-bit LED driver optimized for Red/Green/Green/Blue (RGGB) or Red/Green/Blue/Amber (RGBA) color mixing applications. It is equipped with four individual PWM controllers. Each LED output has its own 8-bit resolution (256 steps) fixed frequency Individual PWM controller that operates at 97 kHz with a duty cycle that is adjustable from 0 % to 99.6 % to allow the LED to be set to a specific brightness value. A fifth 8-bit resolution (256 steps) Group PWM controller has both a fixed frequency of 190 Hz and an adjustable frequency between 24 Hz to once every 10.73 seconds with a duty cycle that is adjustable from 0 % to 99.6 % that is used to either dim or blink all LEDs with the same value. Each LED output can be off, on (no PWM control), set at its Individual PWM controller value or at both Individual and Group PWM controller values. The LED output driver can be programmed to be either open-drain with a 25 mA current sink capability at 5 V or totem-pole with a 25 mA sink, 10 mA source capability at 5 V. The PCA9633 operates with a supply voltage range of 2.3 V to 5.5 V and the outputs are 5.5 V tolerant. Fig 5. PWM dimming 002aac794 RR VI GND RB RG RG BSH112 BSP110 PWMR PWMB PWMG

3.2 Functional description

The PCA9633 is configured and controlled by sending commands to the device via an I2C-bus. Like all I2C-bus compatible ICs, PCA9633 has the following advantages:

Only two bus lines are required; a serial data line (SDA) and a serial clock line (SCL).
The simple 2-wire serial I2C-bus minimizes interconnections so ICs have fewer pins and there are not so many PCB tracks. Result: smaller and less expensive PCBs.
Each device connected to the bus is software-addressable by a unique address.
Multiple PCA9633 devices can be connected to the same I2C-bus without the need for address decoders or chip select pins.
Reduced software development time due to simple command byte sequences needed for the control.
Since PCA9633 supports Fast-mode Plus I2C-bus, serial, 8-bit oriented, bidirectional data transfers can be made at up to 1 Mbit/s and is backward compatible with existing Fast-mode and Standard-mode I 2C-bus devices.
The built-in 10× bus drive capability allows longer distance transmission, larger number of components on a single bus needed in architectural lighting and gaming.
Built-in PWM oscillator minimizes component count and cost.
Allows glueless connection of external FETs for driving high brightness LED strings and light bars.
Special Group PWM control feature allows control of multiple units with simple software commands.

3.3 Basic electrical configur ation for using a PCA9633

A typical application circuit used to drive LEDs is shown in Figure 6. The PCA9633 acts like an I2C-bus slave. The I2C-bus master configures the settings for the 4 PWMs and the LED outputs by sending command bytes to the PCA9633 via the 2-wire I2C-bus. For detailed information on the PCA9633 including register definition and command set, refer to the PCA9633 data sheet. (1) OE requires pull-up resistor if control signal from the master is open-drain. Fig 6. PCA9633 typical application PCA9633 LED0 LED1 SDA SCL OE VDD = 2.5 V, 3.3 V or 5.0 V I2C-BUS/SMBus MASTER 002aab286 SDA SCL 10 kΩ OE 10 kΩ LED2 LED3 VDD VSS 5 V 10 kΩ(1) 12 V

3.4 Driving light ba rs with a PCA9633

[2] V F tolerance is ±1.0 V. [3] Measured at T j =2 5 °C, applicable from IF = 50 mA onwards. [4] Dynamic resistance is the inverse slope of the forw ard current versus forward voltage characteristic. A DC supply rail of 45 V or greater is needed to drive the LED strings. not offered as a part of the solution. must be able to withstand 45 V minimum. Table 1. Electrical characteristics

AN10579_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 1 February 2007 10 of 16 NXP Semiconductors AN10579 Driving LED light bars using NXP solutions (1) OE requires pull-up resistor if control signal from the master is open-drain. Fig 7. PWM control of LED strings PCA9633 LED0 LED1 SDA SCL OE VDD = 5 V I2C-BUS/SMBus MASTER 002aac795 SDA SCL 10 kΩ OE 10 kΩ LED2 LED3 VDD VSS 10 kΩ(1) RR LED supply = 45 V RB RG RG BSH112 BSP110

3.5 Individual brightness control wi th group dimming/blinking with

A 97 kHz fixed frequency signal with programmable duty cycle (8 bits, 256 steps) is used to control individually the brightness for each LED string. On top of this signal (see Figure 8), one of the following signals can be superimposed (this signal can be applied to the 4 LED outputs):

A lower 190 Hz fixed frequency signal with programmable duty cycle (8 bits, 256 steps) is used to provide a global brightness control.
A programmable frequency signal from 24 Hz to 1⁄10.73 Hz (8 bits, 256 steps) with programmable duty cycle (8 bits, 256 steps) is used to provide a global blinking control. Minimum pulse width for LEDn Brightness Control is 40 ns. Minimum pulse width for Group Dimming is 20.48 µs. When M = 1 (GRPPWM register value), the resulting LEDn Brightness Control + Group Dimming signal will have 2 pulses of the LED Brightness Control signal (pulse width = N × 40 ns, with ‘N’ defined in PWMx register). This resulting Brightness + Group Dimming signal above shows a resulting Control signal with M = 4 (8 pulses). Fig 8. Brightness + Group Dimming signals 123456789 1 0 1 1 1 2 507508509510511512 123456789 1 0 1 1 Brightness Control signal (LEDn) M × 256 × 2 × 40 ns with M = (0 to 255) (GRPPWM Register) N × 40 ns with N = (0 to 255) (PWMx Register) 256 × 40 ns = 10.24 µs (97.6 kHz) 1234567812345678 Group Dimming signal resulting Brightness + Group Dimming signal 256 × 2 × 256 × 40 ns = 5.24 ms (190.7 Hz) 002aab417

3.6 Color mixing and control

Color mixing is based on the RGB additive color model as shown in Figure 9. RGB model uses additive color mixing, because it describes what kind of light needs to be emitted to produce a given color. Various ratios of the emitted light for the 3 colors determine the resulting color. Human eye sees the sum of primary colors’ average brightness: X % Red + Y % Green + Z % Blue Brightness of each color LED string is adjusted using the individual PWMs on the PCA9633. Figure 10 shows an example waveform for color mixing using PWMs. Brightness for each primary color (desired amount of each primary color) is controlled with the duty cycle of PWMs. To perform color mixing the frequency of PWM should be high enough so that the human eye does not see the ON/OFF phases that could result in unwanted flicker. Fig 9. The RGB color model 002aac796 Fig 10. PWM waveforms for LED color mixing voltage on red LED driver ONRED <Ired> voltage on green LED driver ONGREEN <Igreen> frequency > 80 Hz to 100 Hz voltage on blue LED driver <Iblue> resulting color ONBLUE 002aac797

AN10579_1 © NXP B.V. 2007. All rights reserved. Application note Rev. 01 — 1 February 2007 13 of 16 NXP Semiconductors AN10579 Driving LED light bars using NXP solutions 4. NXP power solutions for LED supply As mentioned earlier, a DC supply rail of 45 V or greater is needed to drive the LED strings used in the Light bars. This is best done using an offline power supply. NXP's highly efficient STARplug+ range of controller ICs for low-power switched mode power supplies (SMPSs) are well-suited for this application. STARplug+ products operate directly from rectified universal mains supplies: 80 V to 276 V. Essentially turnkey solutions, they dramatically cut design-in time for new power supplies in many applications. STARplug+ devices are manufactured using NXP's high-voltage EZ-HV process. This technology allows analog, digital and power circuitry to be implemented on the same chip. Combined with a low-voltage BiCMOS process, it enables low-power, low-cost and extremely compact solutions for power plugs and small supplies including power supply for LED light bars. All STARplug+ devices feature an integrated power switch, reducing the external component count and bill of materials. Figure 11 shows one such power supply that provides 45 V for the LED light bar. The 120 V AC input voltage is rectified by a full bridge. A small filter or smoothing capacitor is used to hold the rectified voltage to approximately +170 V DC. The unregulated 170 VDC is connected to the input of the STARplug+ family switched mode controller chip that is configured for buck mode operation. For more detailed information on NXP’s power conversion solutions go to: http://www.nxp.com/products/power_management/conversion/starplug/index.html Fig 11. Offline LED power supply using STARplug+ fly-back converter TEA152x AUX VCC RC 002aac798 RREG1 REG DRAIN SOURCEGND RSOURCE OCP RREG2 regulation RAUX demag supply CVCC Co output selection Z1 45 V LED supply CoscRosc oscillator C VI

120 VAC

8.1 Definitions

Draft — The document is a draft version only. The content is still under internal review and subject to formal approval, which may result in modifications or additions. NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information.

8.2 Disclaimers

General — Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. Right to make changes — NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. This document supersedes and replaces all information supplied prior to the publication hereof. Suitability for use — NXP Semiconductors products are not designed, authorized or warranted to be suitable for use in medical, military, aircraft, space or life support equipment, nor in applications where failure or malfunction of a NXP Semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental damage. NXP Semiconductors accepts no liability for inclusion and/or use of NXP Semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer’s own risk. Applications — Applications that are described herein for any of these products are for illustrative purposes only. NXP Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification.

8.3 Trademarks

Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. I2C-bus — logo is a trademark of NXP B.V. STARplug+ — is a trademark of NXP B.V.

NXP Semiconductors AN10579 Driving LED light bars using NXP solutions © NXP B.V. 2007. All rights reserved. For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com Date of release: 1 February 2007 Document identifier: AN10579_1 Please be aware that important notices concerning this document and the product(s) described herein, have been included in section ‘Legal information’. 9. Contents

3.3 Basic electrical configuration for using

3.5 Individual brightness control with group

Product Information

AN10579 specifications and overview.

Summary

Driving LED light bars using NXP solutions Rev. 01-1 February 2007

Description

Driving LED light bars using NXP solutions Rev. 01-1 February 2007

Source title AN10579_15 Datasheet(PDF) - NXP Semiconductors

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