STR-L3201
High-efficiency buck LED driver with wide input range, analog and PWM dimming support for general lighting
Product Overview
Description
The STR-L3201 is a high-efficiency buck LED driver designed for general lighting applications.
It provides constant current regulation with analog and PWM dimming control.
The wide input voltage range makes it suitable for various input sources including AC-DC adapters and DC supplies.
Product Series
STR
Primary Application
General LED lighting
Key Features
- Wide input voltage range (6V-40V)
- High efficiency up to 96%
- Analog and PWM dimming support
- ±3% current accuracy
- LED open and short protection
- Over-temperature protection
- Low EMI design
- Compact SOP-8 package
Specifications
| Topology | Buck (Step-Down) |
|---|---|
| Input Voltage | 6V to 40V |
| LED String Voltage | Up to 36V |
| Max Output Current | 1A |
| Current Accuracy | ±3% |
| Dimming | Analog (0-2.5V) and PWM |
| Efficiency | Up to 96% |
| Package | SOP-8, ESOP-8 |
| Operating Temperature | -40°C to +85°C |
Applications
General LED lighting
Electronic system design
Downlights and spotlights
Electronic system design
LED bulbs
Electronic system design
Channel letter lighting
Electronic system design
Display backlighting
Electronic system design
FAE Expert Insights
"The STR-L3201 is a versatile LED driver that works well in a wide range of lighting applications. The dual dimming options (analog and PWM) provide flexibility for different control systems. The 96% efficiency helps minimize heat generation in the driver, which is important for thermally constrained lighting fixtures. I've used this driver in numerous downlight and bulb designs with excellent results. The protection features are reliable - I've seen it properly handle LED open and short conditions without damage. For general lighting up to 1A, this is a solid, cost-effective choice."
Dual dimming with 96% efficiency for versatile lighting applications
— Kevin Liu, BeiLuo
Frequently Asked Questions
How many LEDs can STR-L3201 drive?
The number of LEDs depends on the LED forward voltage and input voltage. STR-L3201 supports LED string voltage up to 36V. For typical white LEDs with 3V forward voltage, this allows up to 10-12 LEDs in series. For higher voltage LEDs or longer strings, ensure total LED voltage drop is below the maximum. The driver maintains constant current through the LED string regardless of the number of LEDs (within voltage limits).
Maximum 36V LED string voltage. Calculate based on LED forward voltage.
How do I set the LED current?
LED current is set using a current sense resistor between the CS pin and ground. The formula is: Rsense = Vcs / Iled, where Vcs is the current sense threshold voltage (typically 0.25V) and Iled is the desired LED current. For example, for 350mA LED current: Rsense = 0.25V / 0.35A = 0.714Ω. Use a standard value like 0.68Ω or 0.75Ω. The resistor power rating should be at least 2x the calculated power dissipation (P = I² × R).
Calculate using sense threshold voltage. Check datasheet for exact Vcs value.
What is the difference between analog and PWM dimming?
Analog dimming varies the LED current proportionally to a control voltage (0-2.5V for STR-L3201). Lower current reduces brightness but may shift LED color temperature slightly. PWM dimming switches the LED on/off rapidly (typically 200Hz-1kHz) with variable duty cycle. PWM maintains consistent LED color temperature across brightness levels since LEDs operate at full current when on. Analog is simpler to implement; PWM is better for color-critical applications and wider dimming range.
Use PWM for color-critical applications. Use analog for simpler implementations.
How do I implement PWM dimming?
For PWM dimming, apply a PWM signal (200Hz-1kHz recommended) to the DIM pin of STR-L3201. The duty cycle controls brightness: 100% duty = full brightness, 0% duty = off, 50% duty = half brightness. The PWM frequency should be high enough to avoid visible flicker (>200Hz) but not so high that switching losses become significant. The DIM pin typically accepts 3.3V or 5V logic levels. Connect the PWM source directly to the DIM pin.
Apply 200Hz-1kHz PWM to DIM pin. Use 3.3V or 5V logic levels.
What happens if the LED string opens?
STR-L3201 includes LED open protection. If the LED string opens (disconnected or failed), the driver detects the over-voltage condition and enters protection mode to prevent damage. The driver will typically shut down or enter a hiccup mode, retrying periodically. This protection prevents the output capacitor from charging to excessive voltage when no LED load is present. Once the LED fault is cleared, normal operation resumes.
Open protection is automatic. No external components needed.
Can I parallel multiple STR-L3201 drivers for higher current?
While it's possible to parallel LED drivers, it's generally not recommended due to current sharing issues. Each driver will regulate its own current, but slight variations in reference voltage can cause uneven current distribution. For higher current applications, it's better to use a single higher-current driver (like STR-L3202 for 2A) or split the LED string into multiple independent strings, each with its own driver. This ensures proper current regulation in each string.
Use higher current driver or multiple independent strings instead of paralleling.