Integrated multi-channel high accuracy current control LED driver with low dropout regulator

Abstract

This research describes an integrated multi-channel high accuracy current control LED driver with low dropout regulator implemented in a 0.35um TSMC 2P4M CMOS process. With the new trend of backlighting applications for mobile electronics and portable devices requiring a smaller size, lower cost, lesser noise and accurate current control LED driver, it came up with the idea of integrating more than one design features within a single chip. The analysis of using a capacitor-less low dropout regulator to power the constant current source has been explored, with the implementation of wide range battery voltage of 3V to 5V. Possible load current variations were introduced and verified to output a fixed voltage of 2.8V. With a similar to a regulated cascode current mirror structure used to a multi-channel configuration string of LEDs, the design ensure a current matching of less than 1% error current balance and achieve a high accuracy current control of less than 1% error regardless with LED's forward voltage variation. Moreover, for high end portable device with multimedia applications, dimming frequency can be set to 10MHz. In addition, a switching output is a better approach for managing LED's contrast and brightness adjustment as well as maximizing power consumption, ensuring longer life for driving string of LEDs.