CXLE87144D internal integrated MCU single-wire digital interface, data latch, twelve LED constant current drive and PWM brightness control circuit. Multi-chip cascade is realized through a single-wire digital interface (DI/DO), and the external controller only needs one signal line to control all chips in the system. Chip built-in 5V regulator tube, support 6~24V wide voltage input, suitable for a variety of power environment, widely used in LED display, guardrail tube, point light source and other scenes.
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[ CXLE87144D ]"
In the LED display, decorative lighting and landscape lighting system, multi-channel, high-precision, easy-to-expand driver chip is the core to ensure system performance.CXLE87144D as a twelve channel LED fixedConstant current driveSpecial control circuit, with its high integration,StableThe single-wire cascading capability and excellent output consistency make it ideal for medium and high density LED control. This article will be from the chip architecture, communication protocols, electrical characteristics to practical application solutions, a comprehensive analysis ofCXLE87144D, which helps engineers build efficient and reliable LED drive systems.
1. Chip Overview
CXLE87144D internal integrated MCU single-wire digital interface, data latch, twelve LEDConstant current driveand PWM brightness control circuit. Multi-chip cascade is realized through a single-wire digital interface (DI/DO), and the external controller only needs one signal line to control all chips in the system. Chip built-in 5V regulator, support 6~24VWide voltage input, Suitable for a variety of power supply environments, widely used in LED displays, guardrail tubes, point light sources and other scenes.
2. core features
• Twelve-channel constant current output: Support four groups of RGB output, each group of three channels, a total of 12 constant current control.
• Fixed output current: Each channel constant current 17mA, good output consistency, inter-channel error ≤ ± 2.5%.
• 256 levelPWM Dimming: Support 256 levels per channelbrightness adjustmentTo achieve smooth and delicate brightness changes.
• Single-wire serial cascade: Support automatic shaping forwarding, signal transmissionStableThe number of cascading is theoretically unlimited.
• High refresh rate and transfer rate: Data transmission rate 800Kbps, support 1024-point cascade at 30fps refresh rate.
• High withstand voltage and wide temperature operation: OUT port withstand voltage 24V, working temperature -40 ℃ ~ 85 ℃, adapt to harsh environment.
• Dual package option: SOP16 and DIP16 packages are provided to meet different installation and heat dissipation requirements.
3. electrical characteristics and operating conditions
CXLE87144D has excellent electrical performance:
• The output constant current has high precision, and the error between chips is ≤ ± 5%.
• Quiescent current typically 1.2mA, low power consumption.
• Supports linear and load regulation, outputStableSex is strong.
• Built-in power-on reset circuit, default output blue light (duty cycle 25%) after power-on, convenient for system detection.
3.1. Limit parameters
(1) These levels in the above table, the chip may cause permanent damage to the device and reduce the reliability of the device under long-term use conditions,
We do not recommend that the chip work beyond these limit parameters under any other conditions;
(2) All voltage values are tested relative to the system ground.
3.2. Recommended Scope of Working Conditions
3.3. Electrical characteristics
3.4. Switching characteristics
3.5. Timing characteristics
4. Communication Protocols and Data Formats
The chip uses a single-line return-to-zero code communication, and each frame of data consists of multiple 96-bit data packets and reset signals:
• 96 bits of data per chip: Each group of RGB accounts for 24 bits, and the four groups have 96 bits, which respectively control the PWM duty cycle of R, G and B channels.
• Reset signal: Low level active, used to trigger data to take effect and system reset.
After receiving the 96-bit data, the chip starts to forward the subsequent data, realizing seamless cascade. The controller only needs to send data packets of each chip in turn, and finally send a reset signal to complete the configuration and refresh of the entire link.
4.1. Function Description
The chip uses a single-wire communication mode, using the way of zero code to send signals. After power-on reset, the chip receives
After receiving the data, the DO port starts to forward the data continuously sent by the DIN end to provide input data for the next cascade chip. In
Before forwarding data, DO port has been low level. If DIN inputs the RESET reset signal, the chip will receive 24
The × 4bit data output corresponds to the PWM duty cycle, and the chip waits to receive new data again. After receiving the starting 24 × 4bit data,
Data is forwarded through DO port. The original output of OUTR, OUTG and OUTB pins remains unchanged before the chip receives RESET signal.
The chip uses automatic shaping forwarding technology, the signal will not be distorted attenuation, so that the number of cascades of the chip is not limited by the signal transmission, only.
Limited by the requirements of the speed of the screen.
4.2. Data structure
PWM mode command:
If it is in a 24-bit data packet, the data packet is PWM setting data, and its structure is as follows:
The PWM duty cycle is continuously adjustable from 0-256. When 24 × 4bit data is sent, the high-bit first, and the data is sent in RGB order. Every 24 bits can be
Split into 3 8-bit data to send. Pay attention that the low level time between bytes does not exceed the RESET signal time, otherwise the chip will repeat
If the data is received again after reset, the data transmission cannot be realized.
4.3. Communication rate
Note: The typical cycle time for sending a 1 or 0 code is 1200ns (800KHz).
4.4 data transmission and forwarding
Chip cascading and data transmission and forwarding process: the controller sends data (D1). when chip 1 receives the first 96bit, chip 1 has not
There is forwarding data (D2), then the controller continues to send data, and chip 1 receives the second 96bit, because chip 1 already has the first 96bit,
Therefore, chip 1 forwards the second 96bit through DO, and chip 2 receives the data (D2) forwarded by chip 1. At this time, chip 2 has not yet transferred
Send data (D3); The controller continues to send data, and chip 1 forwards the third 96bit received to chip 2, because chip 2 has already stored
There is a 96bit, so chip 2 forwards the third 96bit (D3), and chip 3 receives the third 96bit. at this time, if the controller sends one
A RESET low-level signal, all chips will reset and decode the 96-bit data received by each chip to control the output of four groups of RGB ports.
After a data refresh cycle, the chip returns to the receive ready state.
5. Typical Application Design Guide
5.1. Cascade and refresh rate calculations.
The system refresh rate is directly related to the number of pixel dots. Take the 800Kbps communication rate as an example:
• Each pixel (RGB) needs to transmit 24 bits of data, which takes 28.8 μs.
• If the system contains 2000 pixels, the single refresh time is 57.6ms, and the refresh rate is about 17Hz, which meets most dynamic display requirements.
The data refresh time is calculated according to how many pixels are cascaded in a system. A group of RGB is usually a pixel (or a segment),
OneCXLE8714The 4D chip can control four groups of RGB.
Calculated according to normal mode:
A BIT transmission maximum rate of 1200ns (frequency 800KHz), a pixel data including red (8BIT), green (8BIT), blue (8BIT)
There are 24BIT bits in total and the transmission time is 24 × 1.2uS = 28.8uS. If there are 2000 pixel points in a system, all displayed pixels will be refreshed at one time.
The time is 28.8uS × 2000=57.6mS (ignoring RESET code time), I .e. the refresh rate per second is: 1 ÷ 57.6 × 1000 & asymp;17.36Hz.
The following is a table of the maximum data refresh rate for the number of cascade points:
If the system does not require a high data refresh rate, there is no requirement for the number of cascaded pixel lattices. As long as the power supply is normal, it is theoretically available
CXLE87144D Infinite Cascade.
5.2. Power Supply Configuration and Resistance Selection
Configure the VDD series resistance based on the supply voltage (DC):
• 6V power supply is recommended to connect 50Ω resistors in series;
• 12V power supply recommended in series 650Ω resistance;
• 24V power supply is recommended to connect 1.8kΩ resistors in series.
CXLE87144D can be configured as 6~24V voltage power supply, but according to different input voltage, different power supply resistance should be configured, resistance calculation
Method: Because in practical application, the power supply voltage will decrease with the increase of the load. So set the current flowing through the VDD pin at 10mA
Therefore, the resistor R =(DC-5.5V)/10mA(DC is the power supply voltage) connected in series with VDD.
5.3. Constant current optimization and voltage control
In order to ensure that the chip works in the best state, the OUT port voltage is recommended to be controlled between 1.2V and 3V. High voltage will lead to increased chip power consumption, heat serious. Design can
Adjust the voltage through the series resistance, the formula is as follows:
For example, 24V system drives 6 LEDs (each with a voltage drop of 2V). When the constant current is 17mA, the series resistance is about 525 Ω.
CXLE87144D output is fixedConstant current driveAccording to the constant current curve, it can be seen that when the constant current is 17mA, it enters the constant current area OUT
The terminal voltage needs to be above 1.2V, then the chip has a constant current effect, but it is not the higher the OUT terminal voltage, the better, the higher the voltage, and the drop on the chip.
The greater the power consumption, the serious chip heating, reducing the reliability of the entire system, so it is recommended that the voltage Vout is controlled between 1.2~3V when the OUT terminal is turned on.
Good, commonly used series resistance method to use, the following is the choice of resistance theory calculation method:
System drive voltage: VDD
Single LED conduction voltage drop: Vled
Number of series LEDs: n
Constant current value: Iout
Constant current voltage: 1.5V
Resistance: R
R =(VDD-1.5-n × Vled)/ Iout
For example, the system power supply is 24V, the conduction voltage drop of a single LED is 2V, the number of LEDs in series is 6, and the constant current value is 17mA, which can be calculated according to the above formula
Yes: R =(24-1.5-2 × 6)/0.02=525 Ω, only 525Ω resistor is connected in series to the OUT pin.
5.4. Expanding the flow scheme.
For larger drive currents, multiple OUT ports can be used in parallel. For each parallel connection, the maximum output current increases by 17mA, and the maximum output current can reach 51mA after three parallel connections. This method requires software cooperation,
Set multiple sets of register values to achieve accurate current control and high brightness drive.
CXLE8714Each OUT terminal of 4D can only output 17mA constant current at most. If the user needs to expand the constant current value drive, three OUT terminals can be short
After use, for each OUT terminal short-circuited, the maximum constant current value will be increased by 17mA, and the maximum constant current value will be about 51mA after three short-circuiting, but this side
The disadvantage of the method is that the software needs to cooperate with the control at the same time and write three sets of register values respectively. The advantage is that the desired current value and constant current current can be accurately obtained.
5.5. The LED method is driven by the program.
5.5.1 To realize the brightness control of the LED by the chip, first ensure that the RGB port voltage can make the chip enter constant current operation (refer to "constant
flow curve ").
5.5.2 The chip is powered on reset, the port voltage reaches 1.2V, and the output channel RGB fixed constant current current is 17mA, then the maximum power is allowed to flow
The flow is 17mA.
5.5.3 Keep changing the value of PWM, you can adjust the LED brightness as you like. Set PWM value to 0, output full high, LED off. Set PWM
The value is FFH, the output maximum low-level duty cycle, and the LED is the brightest.
5.5.4 constant current curve
WillCXLE8714When 4D is applied to the LED panel design, the current difference between channels and even between chips is extremely small. This originates fromCXLE8714Excellent for 4D.
Features:
In addition, when the load terminal voltage changes, its output currentStableSex is not affected, as shown in Figure 8 below.
►►CXLE8714The 4D port drive current is a fixed constant current value.
6. typicalapplication circuit
CXLE87144D is widely used in LED display, RGB decorative lighting, landscape lighting and other scenes. In the design, attention should be paid:
• 100Ω resistor in series with DIN/DO pin to prevent hot plug damage;
• Connect the 104 capacitor between VDD and GND, and try to be close to the chip pin to improve the system.Stableof sex;
• The signal line should be shielded to avoid interference in long-distance transmission.
7. Constant Current Performance and Thermal Management
CXLE87144D is excellent in constant current output. When the OUT port voltage exceeds 1.2V, it enters the constant current region, and the output current basically does not change with the voltage. Its excellent constant current characteristics and thermal resistance as low as 79.2 ℃/W make it possible to maintain even in high-density, multi-channel systems.StableWork.
8. epilogue
CXLE87144D with its twelve-channel high integration,StableThe single-wire cascade capability, high-precision output and flexible flow expansion scheme perform well in the field of medium and high density LED control. Whether it is a complex full-color display or a large-scale decorative lighting system, it can provide reliable hardware support. JTMIC (jtm-ic.com) as the official technology partner of the chip, offering fromSample ApplicationOne-stop service from technical guidance to bulk supply.
For detailed data sheets, design tools or sample support, please visit the JTMIC website or contact our technical team.
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