White LEDs are widely used in small liquid crystal display (LCD) panel and keyboard backlight and indicator applications. High-brightness LEDs are used as flash light sources for mobile phones and digital cameras. These applications require optimized driver solutions that can extend battery life and reduce printed circuit board (PCB) area and height. In these application areas, common LED driver solutions involve different topologies of linear, inductive or charge pump types, each with its own characteristics. For example, the inductive solution has the best overall energy efficiency; the charge pump solution uses low-profile ceramic capacitors, which consumes very little board area and height; the linear solution is ideal for color indicators and simple backlight applications. ON Semiconductor provides LED driver solutions for all three types of topologies (see Figure 1) to meet users' different application needs.
Figure 1: Examples of different LED driver topologies for low-voltage portable equipment applications
In terms of charge pump solutions, ON Semiconductor provides products that support different dimming types, such as single-mode, dual-mode, three-mode or four-mode charge pump solutions, such as CAT3200, NCP5602, NCP5612, NCP5623, CAT3606, CAT3616, CAT3626 , CAT3603, CAT3 *, CAT3 *, NCP5603, etc. Taking NCP5623 as an example, this is a high-efficiency LED driver in a 2.0 mm & TImes; 2.0 mm & TImes; 0.55 mm LLGA-12 lead-free package, with I2C interface, built-in progressive dimming function, specially designed to drive mobile phones and other portable products RGB LED decorative light and enhanced LCD backlight. The NCP5623 achieves a peak energy efficiency of 94% and a standby current of less than 1 microampere, extending the battery operating time of portable devices to the longest. For typical applications, in addition to the advantages of extremely small IC packages, the device also has the characteristics of requiring only four passive components to work. The device also has short-circuit and overvoltage protection to protect the system when the LED fails.
It is worth mentioning that ON Semiconductor also provides a variety of four-mode charge pump LED drivers, such as CAT3636, CAT3637, CAT3 * V, CAT3643, CAT3 *, CAT3647, CAT3648, and NCP5 * A / B. Taking CAT3648 as an example, this is a patented high-efficiency quad-mode (Quad-Mode?) Adaptive fractional type (fracTIonal) LED driver of ON Semiconductor, which can drive up to 4 LEDs with a current of 25 mA (see figure 1) Energy efficiency is as high as 92%. This four-mode driver provides four modes: 1x, 1.33x, 1.5x, and 2x. Compared with most charge pump drivers that provide three modes of 1x, 1.5x, and 2x, the energy efficiency is 10% higher, and no additional capacitors are required. Take LED driver performance to a new level. These drivers are suitable for driving white LEDs in small-size LCD backlight and LED flash applications for low-voltage portable devices.
In terms of inductive boost solutions, ON Semiconductor offers different products that use PWM dimming methods, such as CAT32, CAT37, CAT4137, CAT4139, CAT4237, CAT4238 and NCP5005, NCP5010 with output current between 20 mA and 50 mA CAT4240 (250 mA), NCP5050 (600 mA) and NCP1422 (800 mA) that provide greater output current. These inductive boost drivers are suitable for driving white LEDs in low-voltage portable device backlight and flash applications.
In terms of linear backlight driver solutions, ON Semiconductor offers a variety of single-mode LED drivers with 2 to 4 channels, such as CAT4002A, CAT4002B, CAT4003B, CAT4004A, and CAT4004B. These backlight drivers provide 32-level dimming control, provide a fixed or adjustable output current of 25 mA and an extremely low shutdown current of less than 1 μA, and no switching power supply noise problems. These single-mode LED drivers are usually used as part of a system-level approach to design backlight circuits that integrate low-voltage LEDs and simple LED drivers. These driver circuits are simple, helping to extend battery life, reduce costs (such as saving external capacitors), and reduce noise, and provide a simple solution for entry-level portable products and low-cost mobile phone markets.
Figure 2: CAT4002B application circuit diagram
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