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 |
|
Front page boost schematic
|