LED full color display driver chip classification and performance parameters

The LED full-color display driver chip is an important part of the display. Different driving methods of the LED chip can obtain different visual image display effects. Therefore, the advantages and disadvantages of the driver chip are good or bad for the display of the full-color LED display. An important role.

1, LED driver chip is classified into the following two

General-purpose chip: It is used in low-end LED screen production. The commonly used general-purpose chip is 74HC595, which has 8-bit latch, string--shift storage and tri-state output. Each channel can output 35 mA (not constant current).

Special chip: One feature of the dedicated chip is to supply a constant current source. Since the LED is a current characteristic device, that is, under the premise of saturation conduction, its brightness changes with the change of the current magnitude, not with the change of the voltage between the two ends. And change. The constant current source can ensure the stable driving of the LED and eliminate the sparkling phenomenon of the LED.

2, LED display chip important parameters

Maximum output current: The current mainstream constant current source chip has a maximum output current of about 90 mA. Constant current is the basic feature of a dedicated chip and is also the basis for high image quality. The maximum value of the constant current output per channel (ie, the maximum constant output current) is more meaningful to the display, because in the white balance condition, each channel is requested to output a constant current at the same time.

Current output error: The current output error is divided into two types, one is the current error between the bits, that is, the error between each output of the same chip; the other is the current error between the chips, that is, the error of the output current between different chips. . The current output error is a very important parameter, which has a great influence on the uniformity of the full color display. The larger the error, the worse the uniformity of the display screen, and it is difficult to make the screen reach white balance. At present, the bit-to-bit current error of the mainstream constant current source chip is generally within +60%, and the chip to chip inter-chip current error is within ±15%.

The number of constant current source transmissions: There are two types of constant current source transmission, such as 8-channel constant source and 16-channel constant source. Now 16-bit source is dominant. The advantage is that LED driver chip size is small, which is convenient for LED driver board (PCB). Wiring is more advantageous for LED driver boards with smaller dot pitches.

Data Shift Clock: The data shift clock determines the transmission speed of the display data and is a key indicator that affects the update rate of the display. As a large-size display device, the display refresh rate should be above 85 Hz to ensure a stable picture (no scanning brilliance). A higher data shift clock is the basis for the display to obtain a high refresh rate picture. At present, the mainstream constant current source driver chip shift clock frequency is generally above 15 MHz.