SY21145RAC - High Efficiency Fast Response, 4A, 23V Input Synchronous Step Down Regulator


  • Low RDS(ON) for Internal Switches (Top/Bottom): 85/35mΩ
  • Wide Input Voltage Range: 4~23V
  • Instant PWM Architecture to Achieve Fast Transient Responses
  • Internal 600µs Soft-start Limits the Inrush Current
  • Pseudo-constant Frequency: 500kHz
  • 4A Output Current Capability
  • ±1% Internal Reference Voltage
  • Optional Bypass Input
  • Power Good Indicator
  • Output Discharge Function
  • Output Current Limit Protection
  • Latch off Mode Output Under Voltage Protection
  • Latch off Mode Output Over Voltage Protection
  • Programmable Bottom FET Current Limit
  • Input Under Voltage Lock-out(UVLO)
  • Latch off Mode Over Temperature Protection
  • RoHS Compliant and Halogen Free
  • Compact Package: QFN3×3-20

Typical Application


The SY21145 develops a high efficiency synchronous step-down DC/DC regulator capable of delivering 4A current over a wide input voltage range of 4V to 23V.

Silergy’s proprietary Instant-PWM™ fast-response, constant-on-time (COT) PWM control method supports high input/output voltage ratios (low duty cycles), and fast transient response while maintaining a near constant operating frequency over line, load and output voltage ranges. This control method provides stable operation without complex compensation and even with low ESR ceramic capacitors.

Internal 85mΩ power and 35mΩ synchronous rectifier switches provide excellent efficiency over a range of applications, especially for low output voltages and low duty cycles. SY21145 also integrates a bypass switch which allows the IC to be powered by external DC source. Cycle-by-cycle current limit, input under voltage lock-out, internal soft-start, output under voltage protection and over voltage protection, and thermal shutdown provide safe operation in all operating conditions. The SY21145 is available in a compact QFN3×3-20 package.


  • LCD-TV/Net-TV/3DTV
  • Set Top Box
  • Notebook
  • High Power AP