N-Channel Controllers for Constant Current LED Drivers - LM3421


N-Channel Controllers for Constant Current LED Drivers


The LM3421/23 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 LM3421/23 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 LM3421/23 uses 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 LM3421/23 devices 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 2.0 MHz, thus enabling compact solutions. Additional features include "zero current" shutdown, analog dimming, PWM dimming, over-voltage protection, under-voltage lock-out, 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.

The LM3421Q1/23Q1 are AEC-Q100 grade 1 qualified and LM3421Q0/23Q0 are AEC-Q100 grade 0 qualified.


  • 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)
  • Fault Status Flag and Timer (LM3423/23Q1/23Q0 Only)

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Parametrics Compare all products in LED Lighting - Illumination

Input Voltage (Type)
Vin (Min) (V)
Vin (Max) (V)
Iout (Max) (A)
Vout (Min) (V)
Vout (Max) (V)
Regulated Outputs (#)
Dimming Method
Switching Frequency (Min) (kHz)
Switching Frequency (Max) (kHz)
Iq (Typ) (mA)
Vref (V)
UVLO Thresholds On/Off (V)
Special Features
Operating Temperature Range (C)
Approx. Price (US$)
LM3421 LM3421-Q1
DC/DC     DC/DC    
4.5     4.5    
75     75    
5     5    
3     3    
72     72    
1     1    
Boost Controller
Boost Controller
Inductive     Inductive    
100     100    
2000     2000    
2     2    
1.24     1.24    
4.17 / 4.08     4.17 / 4.08    
Adjustable Switch Frequency
Thermal Shutdown    
Adjustable Switch Frequency
Thermal Shutdown    
Catalog     Automotive    
-40 to 125     -40 to 125
-40 to 150    
16HTSSOP     16HTSSOP    
1.15 | 1ku     1.32 | 1ku    

Other qualified versions of LM3421

Version Part Number Definition
Automotive LM3421-Q1 Q100 devices qualified for high-reliability automotive applications targeting zero defects
4.5 <=

V in Lower

V in Upper
<= 75.0
Ambient Temp  °C <= 125
Light Output (optional)  Lumens

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