STR-B3401
High-efficiency synchronous buck converter with 3A output current, wide input range, and compact SOT23-5 package
Product Overview
Description
The STR-B3401 is a high-efficiency synchronous buck converter capable of delivering up to 3A output current.
It features a wide input voltage range and integrated high and low-side MOSFETs for high efficiency.
The compact SOT23-5 package makes it ideal for space-constrained applications.
Product Series
STR
Primary Application
Point-of-load power supplies
Key Features
- Integrated high and low-side MOSFETs
- Wide input voltage range (4.5V-18V)
- High efficiency up to 95%
- 500kHz fixed frequency operation
- Internal compensation for easy design
- Power good indicator
- Over-current and thermal protection
- Compact SOT23-5 package
Specifications
| Input Voltage | 4.5V to 18V |
|---|---|
| Output Voltage | 0.8V to 16V (adjustable) |
| Max Output Current | 3A |
| Switching Frequency | 500kHz |
| Efficiency | Up to 95% |
| Quiescent Current | < 1mA |
| Package | SOT23-5 |
| Operating Temperature | -40°C to +85°C |
Applications
Point-of-load power supplies
Electronic system design
Set-top boxes
Electronic system design
CPE equipment
Electronic system design
Industrial applications
Industrial automation and control
Consumer electronics
Consumer electronics
FAE Expert Insights
"The STR-B3401 is a versatile buck converter that delivers excellent performance in a tiny package. The 3A capability in SOT23-5 is impressive and makes it perfect for compact designs. The efficiency is consistently high across the load range, and the internal compensation really simplifies the design process - no need to calculate external compensation components. I've used this in numerous designs from set-top boxes to industrial modules, and it performs reliably every time. For designers needing high current in limited space, this is an excellent choice."
3A capability in compact SOT23-5 package with 95% efficiency
— Lisa Wang, BeiLuo
Frequently Asked Questions
What is the maximum output current of STR-B3401?
The STR-B3401 is rated for 3A maximum output current. The actual continuous current capability depends on input voltage, output voltage, ambient temperature, and thermal design. At higher input-output voltage differentials, thermal limitations may reduce maximum current. The integrated MOSFETs have low RDS(on) to minimize conduction losses. For reliable operation, ensure adequate copper area for heat dissipation and consider derating at high ambient temperatures.
3A rated current. Ensure proper thermal design for continuous operation at maximum current.
How do I set the output voltage?
Output voltage is set using external resistor dividers connected to the FB pin. The feedback reference voltage is 0.8V. Calculate resistor values using: Vout = 0.8V × (1 + R1/R2). For example, for 3.3V output: R1/R2 = (3.3/0.8) - 1 = 3.125. Use standard values like R1=22kΩ, R2=6.8kΩ. Place feedback resistors close to the IC and keep FB trace short. The datasheet provides recommended values for common output voltages.
Use resistor dividers with 0.8V reference. Place close to IC for noise immunity.
What input capacitors are recommended?
Use ceramic capacitors with X5R or X7R dielectric for input filtering. Recommended value is 10μF or larger, rated for the maximum input voltage with margin. Place the input capacitor as close as possible to the VIN and GND pins to minimize switching loop area. For applications with long input leads or significant input inductance, add additional bulk capacitance (47-100μF electrolytic) to prevent input voltage ringing.
Use 10μF+ ceramic capacitors close to IC. Add bulk capacitance if needed for long leads.
Can STR-B3401 operate at 100% duty cycle?
The STR-B3401 has a maximum duty cycle limit (typically 90-95%) to ensure proper bootstrap capacitor charging for the high-side MOSFET driver. This means the output voltage cannot be equal to the input voltage - there will always be some dropout voltage. For applications requiring dropout operation (Vout ≈ Vin), consider using a buck converter with 100% duty cycle capability or an LDO for the dropout region.
Maximum 90-95% duty cycle. Consider dropout requirements in design.
What is the switching frequency of STR-B3401?
The STR-B3401 operates at a fixed 500kHz switching frequency. This frequency provides a good balance between efficiency, component size, and EMI. The 500kHz allows reasonably small inductors while maintaining good efficiency. The fixed frequency simplifies EMI filter design compared to variable frequency converters. For applications requiring different frequencies, consider other models in the Starrystone Tech portfolio.
Fixed 500kHz operation. Suitable for most applications. Consider EMI in PCB layout.
How do I calculate power dissipation and thermal design?
Power dissipation can be estimated using: Pd = Iout × (1 - Efficiency) × Vout/Vin, or more accurately by calculating conduction and switching losses. Conduction loss = Iout² × RDS(on) × duty cycle. Switching loss depends on switching frequency and transition times. For thermal design, ensure junction temperature stays below 125°C. Calculate temperature rise: ΔT = Pd × θja, where θja is thermal resistance. Provide adequate copper area (typically 20-50mm² for 1-2W dissipation).
Calculate losses and ensure Tj < 125°C. Provide adequate copper area for heat dissipation.