N-Channel Controllers for Constant Current LED Drivers - LM3421


N-Channel Controllers for Constant Current LED Drivers


Recommended alternative parts

  • TPS92691  -  High-side and low-side current sense and series dimming capable, continuous LED current monitoring


The LM3421 and LM3423 family of devices 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 75 V, makes the LM3421 and LM3423 devices 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 devices 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 a high-voltage start-up regulator that operates over a wide input range of 4.5 V to 75 V. The internal PWM controller is designed for adjustable switching frequencies of up to 2 MHz, thus enabling compact solutions.


  • LM3421Q1/LM3423Q1 are Automotive Grade
    Products That are AEC-Q100 Grade 1 Qualified
  • LM3421Q0/LM3423Q0 are Automotive Grade
    Products That are AEC-Q100 Grade 0 Qualified
  • VIN Range From 4.5 V to 75 V
  • High-Side Adjustable Current Sense
  • 2-&3937;, 1-A Peak MOSFET Gate Driver
  • Input Undervoltage and Output Overvoltage
  • 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
  • Fault Status Flag and Timer (LM3423/23Q1/23Q0

View more

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
Buck-Boost Controller
Sepic 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

WEBENCH® Designer LM3421

  V in Lower V in Upper
4.5 ≤  V  V ≤ 75.0
Ambient Temp  °C ≤ 125°C
Light Output (optional)  Lumens