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LM3421 and LM3423 Controllers


National Semiconductor N-channel controllers for constant current LED drivers


National Semiconductor's LM3421 and LM3423 are versatile high voltage N-channel MosFET controllers for LED drivers. They can be easily configured in buck, boost, buck-boost, and SEPIC topologies. This flexibility, along with an input voltage rating of 75V, makes the LM3421 and LM3423 ideal for illuminating LEDs in a large family of applications.

Adjustable high-side current sense voltage allows for tight regulation of the LED current with the highest efficiency possible. The LM3421 and LM3423 use predictive off-time (PRO) control, which is a combination of peak current-mode control and a predictive off-timer. This method of control eases the design of loop compensation while providing inherent input voltage feed-forward compensation.

The LM3421 and LM3423 devices include high-voltage startup regulators that operate over a wide input range of 4.5V to 75V. The internal PWM controller is designed for adjustable switching frequencies of up to 2.0 MHz, thus enabling compact solutions.
National Semiconductor's LM3421 & LM3423

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Features Applications
  • LM3421Q1/LM3423Q1 are automotive grade products that are AEC-Q100 grade 1 qualified (-40°C to 125°C operating junction temperature) and similarly LM3421Q0/LM3423Q0 are AEC-Q100 grade 0 qualified (-40°C to 150°C operating junction temperature)
  • Vin range from 4.5V to 75V
  • High-side adjustable current sense
  • 2Ω, 1A peak MosFET gate driver
  • Input under-voltage and output over-voltage protection
  • PWM and analog dimming
  • Cycle-by-cycle current limit
  • Programmable switching frequency
  • "Zero current" shutdown and thermal shutdown
  • LED output status flag (LM3423/23Q1/23Q0 only)
  • Faults status flag and timer (LM3423/23Q1/23Q0 only)
  • LED drivers - buck, boost, buck-boost, and SEPIC
  • Indoor and outdoor area SSL
  • Automotive
  • General illumination
  • Constant-current regulators
Buck Dimming Circuit

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Digi-Key P/N Manufacturer P/N Description  
LM3421MH-ND LM3421MH/NOPB IC LED DRVR HP CONS CURR 16TSSOP High-Capacitance MLCC Datasheet
LM3423MH-ND LM3423MH/NOPB IC LED DRVR HP CONS CURR 20TSSOP

Please visit Digi-Key's Lighting Solutions Technology Zone to learn more about National Semiconductor lighting products.