CXLE88138C is a high-performance drive control chip designed for LED display, which integrates many functions such as keyboard scanning interface, constant current drive, data storage and MCU digital interface. The chip uses advanced power CMOS technology, with high-precision constant current output, multi-mode display support and flexible keyboard scanning function, widely used in segment code LED display, industrial control panel, smart home display terminal and other fields. This paper will analyze the technical characteristics, pin function, instruction system, application circuit and electrical parameters of the CXLE88138C in depth, and provide a comprehensive design reference for engineers.
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[ CXLE88138C ]"
CXLE88138C Constant Current LED Driver Controller: Technical Details and Application Guide
CXLE88138C is a high-performance drive control chip designed for LED display, which integrates many functions such as keyboard scanning interface, constant current drive, data storage and MCU digital interface. The chip uses advanced power CMOS technology, with high-precision constant current output, multi-mode display support and flexible keyboard scanning function, widely used in segment code LED display, industrial control panel, smart home display terminal and other fields. This paper will analyze the technical characteristics, pin function, instruction system, application circuit and electrical parameters of the CXLE88138C in depth, and provide a comprehensive design reference for engineers.
1. Chip Overview
CXLE88138C is a multi-function LED drive control dedicated circuit, the internal integration of MCU digital interface, data latch, LED high-voltage drive and keyboard scanning circuit. It uses SOP32 package, compact structure, suitable for high-density LED display module. The chip supports a variety of display modes from 11 segments × 7 bits to 14 segments × 4 bits, with good channel consistency and inter-chip consistency, with a maximum channel difference of only 3% and an inter-chip difference of 6%.
Main characteristics of 2.
2.1. The display mode is flexible.: Support 11 × 7 to 14 × 4 and other segment code combinations;
2.2. Constant current drive: The maximum output voltage of SEG port can reach VDD-1V, and it supports 8-level software adjustable brightness;
2.3. Keyboard ScanningSupport 10 × 3 matrix keyboard scanning;
2.4. Communication InterfaceWith CLK, STB, DIN, DOUT four-wire serial interface;
2.5. Built-in oscillation and reset: Built-in RC oscillation circuit and power-on reset function, simplifying external circuit design;
2.6. Encapsulation form: SOP32, suitable for automatic patch production.
3. pin function details
When DOUT port outputs data, it is N-tube open-drain output. When reading the key, it is necessary to externally connect 1K-10K pull-up resistor, as shown in Figure (1).
The company recommends 10K pull-up resistors. DOUT controls the action of the N tube at the falling edge of the clock. At this time, the reading is unstable. Please refer to Figure (6),
The reading is stable on the rising edge of the clock.
CXLE88138C pins are divided into power class, communication class, display output class and keyboard input class. Among them:
3.1.DOUT(Pin 2): Serial data output, N-tube open-drain output, external pull-up resistor required;
3.2.DIN(Pin 3): Serial data input, support multiplexing with DOUT;
3.3.CLK(Pin 4): clock input, rising edge read data, falling edge output;
3.4.STB(Pin 5): Chip select signal to initiate communication;
3.5.SEG/KS Pin(10~24): segment output and keyboard scanning multiplexing;
3.6.GRID Pins(27~31): bit output, used for digital tube bit selection;
3.7.VDD/GND(9, 25, 26, 29, 32): Power and ground.
4. display and keyboard scanning mechanism
The chip has a built-in 14-byte display register with addresses from COH to CDH, supporting common yin and common yang digital tube drivers. Users can write display data through the serial port, and support two modes of address automatic plus one and fixed address.
The external device transmits the data to the CXLE88138C display register through the serial interface, and the address is 14 byte units from the C0H-CDH, respectively.
The LED lights connected to the chip SEG and the GRID pins correspond to each other, and are allocated as shown in Figure (2). When writing LED display data, according to the display address from low
Bit to high, operating from low to high of data bytes.
4.2. Key scan and key scan data register.
The key sweep matrix is 10 × 3bit, as shown in Figure (3):
The key scan data storage address is shown in Figure (4). After the read key command is issued, the key data BYTE1-BYTE5 bytes are read in turn, and the read data starts from the low bit, where B6 and B7 bits are invalid bits, and the chip output is 0 at this time. When the key corresponding to the K and KS pins of the chip is pressed, the BIT in the corresponding byte is 1.
▲ Note: 1. The CXLE88138C can read up to 5 bytes, and multiple reads are not allowed.
2. Read data bytes can only be read from the BYTE1-BYTE5 in sequence, and cannot be read across bytes. For example: K2 on hardware corresponds to KS10
When the key is pressed, if you want to read the data of this key at this time, you must read the 4BIT bit of the 5th byte before reading the data;
When the three keys K1 and KS10,K2 and KS10,K3 and KS10 are pressed at the same time, the B3,B4 and B5 bits of the data read by BYTE5 are all 1(BYTE5 = #38H).
3. The key combination can only be the same KS, and different K pins can be used as key combination; The same K and different KS pins cannot be made
Key combinations are used.
The keyboard scan is a 10 × 3 matrix structure, and the scan data is stored in a 5-byte key value register. The user needs to read BYTE1 to BYTE5 in sequence, each byte corresponding to a different KS line state. Support key combination detection, but need to pay attention to hardware design to avoid display and key conflict.
5. command system
The first byte entered by DIN after the falling edge of the STB is used as a command. After decoding, the highest two bits B7 and B6 are not distinguished
the same instruction.
If the STB is set high during command or data transmission, serial communication is initialized and the command or data being transmitted is invalid
(Previously transmitted instructions or data remain valid).
CXLE88138C supports four types of directives:
5.1. Display mode setting command.: Set the segment and number of digits;
This instruction is used to set the number of selected segments and bits (4 to 7 bits, 11 to 14 segments). When this instruction is executed, the display is forced to close, requiring
To send the display control command to open the display, the original display of the data content will not be changed. But when the same mode is set, the above case
It doesn't happen. At power-up, the default setting mode is 7-bit 11-segment.
5.2. Data read and write settings command.: Configure the data operation mode;
5.3. Address setting command: Specifies the display register address;
This instruction is used to set the address of the display register.
If the address is set to CEH or higher, the data is ignored until a valid address is set.
At power-on, the address is set to C0H by default.
5.4. Display control commands.: Adjust the brightness and switch display.
The command is input after the falling edge of the STB through DIN, and the upper two bits (B7, B6) are used to distinguish the command type.
6. Serial Communication Timing
The chip supports three communication timings: write data, read data and read keys:
6.1. Data receiving (writing data): Input data on the rising edge of CLK;
6.2. Data reading (reading data): Output data at the falling edge of CLK, pay attention to Twait time (≥ 1μs);
▲ Note: When reading data, one is required from the 8th rising edge of the serial clock CLK to the falling edge of CLK to read data.
Waiting time Twait (minimum 1 μs).
6.3. Display and keys: Read the 5-byte key value in turn after sending the read command.
6.3.1) Display
6.3.1.1) Drive the common-negative digital tube:
Figure (7) shows the connection diagram of the common negative digital tube. If the digital tube displays "0", you need to make SEG1,SEG2,SEG3,SEG4,SEG5,SEG6 high and SEG7 low when GRID1 is low. Look at the address table shown in Figure (2). Just write data 3FH in C0H address unit to make the digital tube display "0".
6.3.1.2) Drive Gongyang Digital Tube:
Figure (8) shows the connection diagram of the common positive digital tube. If the digital tube displays "0", you need to make SEG1 high when GRID1,GRID2,GRID3,GRID4,GRID5 and GRID6 are low and make SEG1 low when GRID7 is low. To write data 01H into address cells C0H,C2H,C4H,C6H,C8H,CAH respectively, and write data 00H into all other address cells.
▲ Note: SEG1-11 is P-tube open-drain output and GRID1-7 is N-tube open-drain output. When in use, SEG1-11 can only be connected to the anode of LED, GRID can only be connected to the cathode of LED, and cannot be connected in reverse.
6.3.1) Key
The key scanning is automatically completed by the CXLE88138C and is not controlled by the user. The user only needs to read the key value according to the time sequence. It takes 2 display cycles to complete a key sweep, and one display cycle takes about T = 8 × 500us. Two different keys are pressed successively in 8MS, and the key values read twice are the key values of the key pressed first.
Observe the output keystroke waveforms of SEG1/KS1 and SEG2/KS2 with an oscilloscope according to Figure (9), as shown in Figure (10).
The waveform of SEGn/KSn when the IC scans the keyboard:
Tdisp is related to the oscillation frequency of IC operation, 500us is for reference only, and the actual measurement shall prevail.
In general, figure (11) can be used to meet the requirements of key design.
When S1 is pressed, "1" is read in B0 of the first byte ". If multiple keys are pressed, multiple "1" will be read. When S2 and S3 are pressed, "1" can be read in B1 and B3 of the first byte ".
▲ Note: Precautions for the use of composite keys:
The SEG1/KS1-SEG10/KS10 display is multiplexed with key scanning. Taking Figure (12) as an example, the display requires D1 to be on and D2 to be off, SEG1 to be "0" and SEG2 to be "1". If S1 and S2 are pressed at the same time, it is equivalent to SEG1 and SEG2 being short-circuited, and D1 and D2 are both lit.
Solution:
1. On the hardware, the keys that need to be pressed at the same time can be set on different K lines as shown in Figure (13),
2. The series resistor on the SEG1-SEG N is shown in Figure (14). The resistance value of the resistor should be selected at 510 ohms, which is too large to cause key failure, and too small to solve the problem of display interference.
3. Or series diodes as shown in Figure (15).
7. Application Circuit Design
7.2. Gongyang digital tube drive circuit:GRID is connected to the anode, SEG is connected to the cathode, and bit selection data is written through multiple address units respectively.
▲ Note: 1. The filter capacitor between VDD and GND should be placed as close to the CXLE88138C chip as possible on the PCB board to enhance the filtering effect.
2. Four 100P capacitors connected to DIN, DOUT, CLK and STB communication ports can reduce interference to the communication ports.
3. Since the conduction voltage of the blue digital tube is about 3V, the CXLE88138C power supply should be 5V.
4. In order to make the chip enter the constant current linear working area, please ensure that the voltage drop between SEG channel and GND is less than 4V.
7.3. Keyboard scanning circuit:K1 ~ K3 for the input line, KS1 ~ KS10 for the output/scan line, external pull-up resistor and filter capacitor to enhance the anti-interference ability.
8. Constant Current Characteristics and Heat Dissipation Design
1. The maximum current error between channels is less than ± 3℉, while the maximum current error between chips is less than ± 6℉.
2. When working in the constant current linear region, it is necessary to ensure that the voltage difference between the SEG pin and GND is less than 4V.
In addition, when the load terminal voltage (VDS) changes, the stability of the output current is not affected, as shown in the following figure:
Package Thermal Power (PD)
CXLE88138C support constant current output, the linear working area requires SEG and GND voltage difference less than 4V. Actual power consumption shall meet:
The relationship between the output current and the constant current ratio is:
9. electrical parameters and timing characteristics
9.1. Working voltage：4.5V~5.5V；
9.2. Output current: SEG port constant current output 28 ~ 40mA;
9.3. Oscillation frequency: 500kHz typical;
9.4. Maximum clock frequency：1MHz；
9.5. Timing characteristics requirements: CLK pulse width ≥ 400ns,STB pulse width ≥ 1μs.
9.6. Limit parameters (Ta = 25 ℃, Vss = 0V)
9.6. Normal operating range (Vss = 0V)
9.7. Electrical characteristics (VDD = 4.5~5.5V, Vss = 0 V
9.8. Switching characteristics (VDD = 4.5~5.5V)
9.9. Timing waveform diagram
Serial data transmission in 10. applications
10.1. Address automatically plus one mode
Using the address automatic plus 1 mode, setting the address is actually setting the starting address for storing the transmitted data stream. Start Address Command Word
After sending, "STB" does not need to be set high followed by data transmission, up to 14BYTE, and "STB" is set high only after data transmission is completed.
Command1: Display Mode Setting command
Command2: Data Read/Write Setting Command
Command3: Display Address Setting command
Data1 ~ n: display data, starting with the address specified by the Command3 (up to 14 bytes)
Command4: Display Control Commands
10.2. Fixed address mode.
Using the fixed address mode, setting the address is actually setting the address where the 1BYTE data to be transmitted is stored. Address sent,
"STB" does not need to be set high, and 1BYTE data is transmitted immediately, and "STB" is set high only after data transmission is completed. Then reset the second data requirement
The address to be stored, up to 14BYTE data transmission is completed, and "STB" is set high.
Command1: Display Mode Setting command
Command2: Data Read/Write Setting Command
Command3: display address setting command, set display address 1
Data1: display data 1, stored in the address unit specified by the Command3
Command4: display address setting command, set display address 2
Data2: display data 2, stored in the address unit specified by the Command4
Command5: Display Control Commands
10.3. Read key timing
Command1: Read Key Commands
Data1 ~ 5: Read key data
10.4. Program design
10.4.1) The program flow chart using the address automatic plus one mode:
10.4.1) Program design flowchart with fixed address:
XI. Summary
CXLE88138C is a feature-rich, stable performance LED driver control chip, suitable for a variety of display and key scanning scenarios. Its constant current output, multi-mode display and flexible communication interface make it ideal for industrial and consumer electronics. Attention should be paid to power supply filtering, signal anti-interference and heat dissipation management during design to ensure stable operation of the system.
Through the detailed analysis of this paper, it is hoped that it can provide practical reference for engineers in CXLE88138C-based product design, and further improve the reliability and performance of products.
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| Model | Number of Interfaces | Number of driving lattice | Segment/Bit | Common Yin Drive | Gongyang drive | Key | Encapsulation form | Remarks |
| CXLE88134N | 3 | 28 | 7*4 | Section 7, 4 digits | - | - | SOP16/DIP16 | LED panel display driver chip |
| CXLE88135N | 3 | 21 | 8*2/7*3 | 8 segments 2 bits/7 segments 3 bits | - | 6*1 | SOP16 | LED panel display driver chip |
| CXLE88136N | 3 | 35 | 5*7/8*4 | 7-segment 5-bit/8-segment 4-bit | Segment 7, position 5 | 5*1 | SOP18/DIP18 | LED panel display driver chip |
| CXLE88137BN | 3 | 48 | 6*7/9*4 | 7 segments 6 bits/9 segments 4 bits | Segment 7, 6 digits | 6*1 | SOP20 | LED panel display driver chip |
| CXLE88137N | 3 | 48 | 8*6/10*4 | 8 segments 6 bits/10 segments 4 bits | - | - | SOP20 | LED panel display driver chip |
| CXLE88138C | 4 | 77 | 11*7/14*4 | 11 segment 7 bits/14 segment 4 bits | Section 7, position 11 | 10*3 | SOP32 | LED panel display driver chip |
| CXLE88138N | 4 | 77 | 11*7/14*4 | 11 segment 7 bits/14 segment 4 bits | Section 7, position 11 | 10*3 | SOP32 | LED panel display driver chip |
| CXLE88139N | 3 | 77 | 11*7/14*4 | 11 segment 7 bits/14 segment 4 bits | Section 7, position 11 | - | SOP24/QSOP24 | LED panel display driver chip |
| CXLE88141N | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*2 | SOP28 | LED panel display driver chip |
| CXLE88142A | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*2 | SOP28 | LED panel display driver chip |
| CXLE88142E | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*2 | SOP28 | LED panel display driver chip |
| CXLE88143AN | 3 | 128 | 16*8 | 16 Segment 8 Bits | 8 Segments 16 Bits | - | SOP32 | LED panel display driver chip |
| CXLE88143BN | 3 | 112 | 14*8 | Segment 14, 8 bits | 8 Segment 14 Bits | 8*2 | SOP32 | LED panel display driver chip |
| CXLE88143CN | 3 | 120 | 15*8 | Segment 15, 8 bits | Segment 8, bit 15 | 8*1 | SOP32 | LED panel display driver chip |
| CXLE88143DN | 3 | 96 | 12*8 | 12 Segment 8 Bits | Segment 8, 12 bits | 8*4 | SOP32 | LED panel display driver chip |
| CXLE88143N | 4 | 128 | 16*8 | 16 Segment 8 Bits | 8 Segments 16 Bits | 8*4 | QFP44 | LED panel display driver chip |
| CXLE88147N | 3 | 80 | 10*8 | Segment 10, 8 bits | 8 Segment 10 Bits | 8*3 | SOP28 | LED panel display driver chip |
| CXLE88148N | 3 | 64 | 8*8 | 8 Segment 8 Bits | Section 8, 6 digits | 4*2 | SOP24/QSOP24 | LED panel display driver chip |
| CXLE88149B | 2 | 128 | 8*16 | 8 Segments 16 Bits | 16 Segment 8 Bits | - | SOP28、SSOP28 | LED panel display driver chip |
| CXLE88155N | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*2 | SOP24/SSOP24/SDIP24 | LED panel display driver chip |
| CXLE88171 | 4 | 77 | 11*7/14*4 | 11 segment 7 bits/14 segment 4 bits | Section 7, position 11 | 10*3 | SOP32 | LED panel display driver chip |
| CXLE88172 | 2 | 128 | 8*16 | 8 Segments 16 Bits | 16 Segment 8 Bits | - | SOP24 | LED panel display driver chip |
| CXLE88173 | 2 | 144 | 8*9*2 | forward and reverse push digital tube | forward and reverse push digital tube | - | QSOP24 | LED panel display driver chip |
| CXLE88174 | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | Touch keys 8 | SOP32 | LED panel display driver chip |
| CXLE88175 | 5 | 120 | 15*8 | Segment 15, 8 bits | Segment 8, bit 15 | 8*1/8 | QFN48 | LED panel display driver chip |
| CXLE88176 | 3 | 77 | 11*7/14*4 | 11 segment 7 bits/14 segment 4 bits | Section 7, position 11 | 10*1 | SOP24 | LED panel display driver chip |
| CXLE88156 | 3 | 128 | 8*16 | 8 Segments 16 Bits | 16 Segment 8 Bits | - | SOP32 | LED panel display driver chip |
| CXLE88134 | 3 | 28 | 7*4 | Section 7, 4 digits | - | - | SOP16/DIP16 | LED panel display driver chip |
| CXLE88135 | 3 | 21 | 8*2/7*3 | 8 segments 2 bits/7 segments 3 bits | - | 6*1 | SOP16 | LED panel display driver chip |
| CXLE88136 | 3 | 35 | 5*7/8*4 | 7-segment 5-bit/8-segment 4-bit | Segment 7, position 5 | 5*1 | SOP18/DIP18 | LED panel display driver chip |
| CXLE88137 | 3 | 48 | 8*6/10*4 | 8 segments 6 bits/10 segments 4 bits | - | - | SOP20 | LED panel display driver chip |
| CXLE88137A | 3 | 48 | 6*7/9*4 | 7 segments 6 bits/9 segments 4 bits | Segment 7, 6 digits | 6*1 | SOP20 | LED panel display driver chip |
| CXLE88138 | 4 | 77 | 11*7/14*4 | 11 segment 7 bits/14 segment 4 bits | Section 7, position 11 | 10*3 | SOP32 | LED panel display driver chip |
| CXLE88139 | 3 | 77 | 11*7/14*4 | 11 segment 7 bits/14 segment 4 bits | Section 7, position 11 | - | SOP24/QSOP24 | LED panel display driver chip |
| CXLE88140A | 4 | 77 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*1 | SOP32 | LED panel display driver chip |
| CXLE88140B | 3 | 77 | 11*7/14*4 | 11 segment 7 bits/14 segment 4 bits | Section 7, position 11 | 10*3 | QFP44 | LED panel display driver chip |
| CXLE88141 | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*2 | SOP28 | LED panel display driver chip |
| CXLE88142 | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*2 | SOP28 | LED panel display driver chip |
| CXLE88143 | 4 | 128 | 16*8 | 16 Segment 8 Bits | 8 Segments 16 Bits | 8*4 | QFP44 | LED panel display driver chip |
| CXLE88143A | 3 | 128 | 16*8 | 16 Segment 8 Bits | 8 Segments 16 Bits | - | SOP32 | LED panel display driver chip |
| CXLE88143B | 3 | 112 | 14*8 | Segment 14, 8 bits | 8 Segment 14 Bits | 8*2 | SOP32 | LED panel display driver chip |
| CXLE88143C | 3 | 120 | 15*8 | Segment 15, 8 bits | Segment 8, bit 15 | 8*1 | SOP32 | LED panel display driver chip |
| CXLE88143D | 3 | 96 | 12*8 | 12 Segment 8 Bits | Segment 8, 12 bits | 8*4 | SOP32 | LED panel display driver chip |
| CXLE88144 | 3 | 35 | 7*5/8*4 | 7-segment 5-bit/8-segment 4-bit | - | 7*1 | DIP18 | LED panel display driver chip |
| CXLE88145 | 2 | 32 | 8*4 | - | Segment 8 4 bits | 8*2 | DIP18 | LED panel display driver chip |
| CXLE88146 | 2 | 48 | 8*6 | - | Section 8, 6 digits | 8*2 | SOP20/DIP20 | LED panel display driver chip |
| CXLE88147 | 3 | 80 | 10*8 | Segment 10, 8 bits | 8 Segment 10 Bits | 8*3 | SOP28 | LED panel display driver chip |
| CXLE88148 | 3 | 64 | 8*8 | 8 Segment 8 Bits | Section 8, 6 digits | 4*2 | SOP24/QSOP24 | LED panel display driver chip |
| CXLE88149 | 2 | 128 | 8*16 | 8 Segments 16 Bits | 16 Segment 8 Bits | - | SOP28/SSOP28 | LED panel display driver chip |
| CXLE88150 | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*2 | SOP28 | LED panel display driver chip |
| CXLE88151 | 2 | 32 | 8*4 | 8-segment 4-bit/7-segment 4-bit | - | 7*4 | SOP16/DIP16 | LED panel display driver chip |
| CXLE88152 | 2 | 28 | 7*4 | - | Section 7, 4 digits | 7*1 | SOP16/DIP16 | LED panel display driver chip |
| CXLE88153 | 1 | 40 | 7*6/8*5 | 7-segment 6-bit/8-segment 5-bit | 6 segments 7 bits/5 segments 8 bits | - | SOP16 | LED panel display driver chip |
| CXLE88154 | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*2 | SOP28 | LED panel display driver chip |
| CXLE88155 | 3 | 70 | 10*7/13*4 | 10 segments 7 bits/13 segments 4 bits | Segment 7, 10 digits | 10*2 | SOP24/SSOP24/SDIP24 | LED panel display driver chip |
| CXLE88133 | 2 | 256 | 32*8/24*16 | 32 segment 8 bit/24 segment 16 bit | 8 segment 32 bit/16 segment 24 bit | - | LQFP48/LQFP52 | LED panel display driver chip |
| CXLE88132 | 4 | 256 | 32*8/24*16 | 32 segment 8 bit/24 segment 16 bit | 8 segment 32 bit/16 segment 24 bit | - | LQFP48/LQFP52 | LED panel display driver chip |
