Features • VIN range from 4.5V to 75V • 2% Internal reference voltage (1.235V) • Current sense voltage adjustable from 20mV • High-side current sensing • 2Ω MOSFET gate driver • Dimming MOSFET gate driver • Input under-voltage protection • Over-voltage protection • Low shutdown current, IQ < 1µA • Fast (50kHz) PWM dimming • Cycle-by-cycle current limit • Programmable switching frequency • LED output status flag (LM3423 only) • Fault timer pin (LM3423 only) • TSSOP EP 16-lead package (LM3421) • TSSOP EP 20-lead package (LM3423) Description The LM3421/LM3423 devices are versatile high voltage LED driver controllers. With the capability to be configured in a Buck, Boost, Buck-Boost (Flyback), or SEPIC topology, and an input operating voltage rating of 75V, these controllers are ideal for illuminating LEDs in a very diverse, large family of applications. Adjustable high-side current sense with a typical sense voltage of 100mV allows for tight regulation of the LED current with the highest efficiency possible. Output LED current regulation is based on peak current-mode control with predictive Off-Time Control. This method of control eases the design of loop compensation while providing inherent input voltage feed-forward compensation. The LM3421/LM3423 include a high-voltage startup regulator that operates over a wide input range of 4.5V to 75V. The internal PWM controller is designed for adjustable switching frequencies of up to 2.0MHz, thus enabling compact solutions. Additional features include: “zero” current shutdown, precision reference, logic compatible DIM input suitable for fast PWM dimming, cycle-by-cycle current limit, and thermal shutdown. The LM3423 also includes an LED output status flag, a fault flag, a programmable fault timer, and a logic input to select the polarity of the dimming output driver. Applications • LED Drivers • Constant-Current Buck-Boost Regulator • Constant-Current Boost Regulator • Constant-Current Flyback Regulator • Constant-Current SEPIC Regulator • Thermo-Electric Cooler (Peltier) Driver

LM3421   4.50 <= V in Lower  V   <= V in Upper  V   <= 75.00 Ambient Temperature  °C <= 100 What are WEBENCH® tools? Front page boost schematic MY BRIEFCASE                                       Click any "Briefcase" icon to add an item

Typical Application click for larger image Front page boost schematic	Block Diagram click for larger image Block diagram
Typical Performance click for larger image

Datasheet

Title		Size	Date	Other Language
	LM3421 , LM3423 N-Channel Controllers for Constant Current LED Drivers	893 Kbytes	26-Jan-09

Featured Application Notes

Title		Size	Date	Other Language
	AN-1907: Application Note 1907 LM3423 Buck-Boost Configuration Evaluation Board	879 Kbytes	8-Dec-08

More Application Notes

Title		Size	Date	Other Language
	AN-1982: Application Note 1982 Small, Wide Input Voltage Range LM2842 Keeps LEDs Cool	63 Kbytes	15-Jul-09
	AN-1872: Application Note 1872 LM3423 Boost Evaluation Board	764 Kbytes	8-Dec-08
	AN-1969: Application Note 1969 LM3424 Boost Evaluation Board	988 Kbytes	22-Aug-09
	AN-1967: Application Note 1967 LM3424 Buck-Boost Evaluation Board	1027 Kbytes	22-Aug-09
	AN-1985: Application Note 1985 LM3429 Buck-Boost Evaluation Board	705 Kbytes	3-Aug-09
	AN-1986: Application Note 1986 LM3429 Boost Evaluation Board	672 Kbytes	3-Aug-09

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM3421MH	ABCD150XV1	0	3868	0	0	2595000	2	736338335
LM3421MHX	ABCD150XV1	0	3868	0	0	2595000	2	736338335

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

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