Design Of The ESD And Surge Protection For Constant Current LED Driver ICs

With the advantages of energy saving,environmental protection and long life,light-emitting diodes(LEDs)have been widely used in display,lighting and backlight driver,helping China to achieve the goal of carbon neutrality.When electrostatic discharge(ESD)and surge issues occur in constant current LED driver integrated circuits(ICs),the LED current fluctuates greatly since LED is a kind of current sensitive component,which is easy to induce the LED brightness va riation,working life reduction,and even causes failure of the driver IC or LEDs.This paper proposes a series of ESD and surge protection solutions to meet the protection requirements for different ports of 5.5 V constant-current LED driver ICs.By ultilizing Sentaurus design tool and transimission line pulse(TLP)test system,the working mechanisms and electrical characteristics of the proposed solutions under electrostatic discharge(ESD)and surge stresses are analyzed and verified.The main research content of this paper is summarized as follows.Firstly,the paper briefly describes the operating principle of the typical constant-current LED driver IC,the design methods and failure judgement methods of ESD and surge protection.The relevant industrial test models and design tools are introduced.The internal physical mechanisms of several typical protection schemes are analyzed by Sentaurus,which provides reference for the novel ESD and surge protection design.Secondly,the whole-chip ESD protection method is adopted in on-chip ESD protection design.Aiming to meet the ESD protection requirements for the I/O ports of 5.5 V constant-current LED driver ICs,such as rapid response and low turn-on resistance,a series of experimental schemes are proposed and fabricated,including the typical dual-diode string(TDS),the diode-triggered silicon controlled rectifier(DTSCR),and the gate-assisted DTSCR with the waffle layout(GDTSCR-WL).Compared with TDS and DTSCR,GDTSCR-WL improves the turn-on speed,figure of merit and turn-on resistance to 10.2 ns,5.8 m A/μm~2 and0.1Ω,respectively.Because GDTSCR-WL introduces the gate-assisted effect of parasitic NMOS and ultilizes waffle layout design method,facilitating the turn on of multiple SCRs.Aiming to meet the dual-direction latch-up-free ESD protection requirements for the power clamp of 5.5 V constant-current LED driver ICs,the three-well dual-direction SCR(TWDDSCR)and the high-doping brigde DDSCR(HDBDDSCR)are designed and fabricated.Compared with TWDDSCR,The ESD robustness of HDBDDSCR is increased from 1.6 A to 4.5 A by adding well resistance to assist in triggering SCR.The high-doping bridges are adopted to suppress the conductance modulation effect,thus the holding voltage is improved to 6.4 V by optimizing the bridge length.Finally,aiming to meet the latch-up-immune and robust surge protection requirements for the operating voltage ports of 5.5 V constant-current LED driver ICs,the low-voltage-triggering SCR(LVTSCR)and the SCR with embedded floating N+and surface NMOS(FNSCR＿SNMOS)are presented and fabricated.Compared with LVTSCR,the holding voltage of FNSCR＿SNMOS is optimized to 10.2 V.And the unit width robustness is strengthened to 51 m A/μm,2.6 times that of LVTSCR.The FNSCR＿SNMOS possesses great protection performance because the surface current path composed of floating N+and NMOS shunts surge current,helpful to improve the uniformity of current discharge.Besides,aiming to meet the surge protection requirements for high voltage output ports of 5.5 V constant-current LED driver ICs,the modified lateral SCR with embedded floating P+(FPMLSCR)and the high-voltage double-snapback SCR(HVDSSCR)are designed and fabricated to achieve high trigger and holding voltage.Compared to FPMLSCR,the HVDSSCR adopts double-snapback technology and regulates the SCR path length to restrain the positive feedback of SCR.Thus the holding voltage is modified to 10.4 V.And HVDSSCR realizes a high trigger voltage of 33.3 V by well breakdown trigger mechanism.In one word,HVDSSCR is a better solution to surge protection of the high voltage output ports.