Intelligent LED control and interface scheme for the application of signs and decorative lighting

With improvement in luminous performance and cost almost all aspects of LED, LED is used more and more widely, but the penetration in various application fields of the proportion or not. In the field of commercial applications such as addressable signs and building lighting, LED is widely used for its advantages in terms of color, overall cost of ownership, working life, reliability and convenience. For example, in building lighting applications, LED can be used to create rich colors on the exterior walls of the building, and to better demonstrate the structure of the building. In the mobile logo application, you can also update the traffic display, video images and billboards.

A Morimi as the first high performance silicon semiconductor applications in high energy electronic products supplier, LED drive scheme offers a wide range for a variety of LED applications, including for a series of linear addressable signs and building decoration lighting of two kinds of commonly used drive (see table below). These drives are able to accurately stabilize the LED current and contain programmable interfaces for software control. In this paper, CAT4008, CAT4103 and CAT9552 as an example, the main functions and the basic working principle are expounded, which is convenient for the selection of the design of the engineer.

Table 1: LED series intelligent A Morimi semiconductor applied to mark and building decorative lighting control / drive.

Constant current drain type LED driver for LED billboards and other applications

Billboard signs, such as scrolling banners, intelligent vehicle logo and sports scoreboard and other LED applications require the use of multiple LED, usually contains more than on LED, LED driving scheme provides constant light output current, inter channel, high precision, easy to provide the interface to control the channel with different LED, and to have reliable protection function. A Morimi semiconductor solutions for such applications, including CAT4008 and CAT4106, such as constant current LED into the type of drive, which supports the 8 channel, which supports the 16 channel.

To CAT4008 as an example, the typical LED channel matching accuracy of + 1.5%, and the LED channel can at low output voltage to 0.4V (when LED current is 2~100 mA) to keep the steady state in the design can achieve the higher power efficiency. Figure 1 shows a block diagram of the CAT4008 on the left and a detailed description of the different pins. See resources for [1]. This device uses 8 closely matched drain current to stabilize the LED current of each channel, while the external resistor RSET is used to set the LED channel current to about RSET times the current of the. Since each channel contains an independent current sensing circuit, the CAT4008 is capable of providing a stable current for all channels. In most current and supply voltage conditions, the maximum LED channel drop is 0.4 V, which helps to improve the heat dissipation and improve the efficiency of the LED driver. On power up, the undervoltage lockout circuit clears all latch and shift register information and sets all outputs to close. Once the undervoltage lockout threshold is reached, the device can be set. The driver will delay the activation time of each successive LED output channel by a factor of 17 ns (), which means that the LED2 is relative to the LED1 delay of about 17 ns, and the LED3 is delayed by a factor of LED1 ns. The delay is introduced when the latch (LATCH) pin is activated, thereby minimizing the inrush current on the LED power supply, thereby enabling the use of smaller bypass capacitors.

Speeds up to 25MHz high-speed, four line (4-Wire) serial interface through the shift register and each LED channel is latched in the 8 channel control architecture. The serial data output pin allows multiple devices to be connected in series using the same serial interface. The CAT4008 also has an output shutdown pin that can be used to turn off all LED channels without having to rely on the serial port to send data. In addition, the CAT4008 also has a thermal protection function to close the LED output when the chip temperature exceeds the allowable limit.

Figure 1: A Morimi semiconductor 8 channel constant current LED input driver CAT4008 block diagram and application examples.

RGB LED pixel driver for high brightness, high visual impact building lighting applications

To create high visual impact effect of building decorative lighting applications use high brightness LED, LED driver can drive high brightness RGB LED, and to have a high speed interface, which supports high data rate and ensure high data integrity, but also need to have the ultra low pressure drop, thereby providing higher energy efficiency.

With three channel independent current control function A Morimi semiconductor suitable for this type of application includes constant current LED driver RGB LED pixel driver CAT4103 and CAT4109. Among them, CAT4103 is a high-end, multi color, "smart" LED building lighting application and design, with high-speed serial interface, can support up to 25 MHz data rate, provide fully buffered output data, to ensure that in the distributed (long distance), maintain the highest data integrity daisy chain type lighting system. The CAT4109 uses a parallel interface, each channel has a special pulse width modulation (PWM) control, is very suitable for more conventional LED visual effects applications, such as mixed color and building key lighting.

Figure 2: A Morimi semiconductor CAT4103 block diagram, a typical application circuit diagram and application examples

CAT4103 and CAT4109 will support a wide range of LED per channel up to 175 mA constant current drive current of 60 mA to 0.3 V pressure level, ensure the highest performance in driving long string LED. These drivers support 25 V voltage levels per channel, capable of supporting RGB pixels with a high brightness power level of more than 10 watts (W).

CAT4103 and CAT4109 are A Morimi semiconductor constant current low dropout drive (LDO) product line two