SY21249TMC - High Efficiency Fast Response, 11A, 28V Input Synchronous Step Down Regulator


  • Low RDS(ON) for Internal Switches (Top/Bottom): 17/7.5 mΩ
  • Wide Input Voltage Range: 4~24V
  • Integrated Bypass Switch: 1.5Ω
  • Instant PWM Architecture to Achieve Fast Transient Responses
  • Internal Soft-start Limits the Inrush Current
  • Pseudo-Constant Frequency: 500kHz
  • Adjustable Output Voltage Application
  • 11A Output Current Capability
  • ±1% Internal Reference Voltage
  • PFM/USM Selectable Light Load Operation Mode
  • Power Good Indicator
  • Output Discharge Function
  • Cycle-by-cycle Valley and Peak Current Limit Protection
  • Programmable Valley Current Limit Threshold by ILMT Pin
  • Latch-off Mode Output Under Voltage Protection
  • Latch-off Mode Output Over Voltage Protection
  • Latch-off Mode Over Temperature Protection
  • Input UVLO
  • RoHS Compliant and Halogen Free
  • Compact Package: QFN3×4-13

Typical Application


The SY21249 develops a high efficiency synchronous step-down DC/DC regulator capable of delivering 11A current. The device integrates main switch and synchronous switch with very low RDS(ON) to minimize the conduction loss. In addition, it operates at pseudo-constant frequency of 500kHz under heavy load conditions to minimize the size of inductor and capacitor.

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.

The SY21249 operates over a wide input voltage range from 4V to 24V. Cycle-by-cycle current limit, input under voltage lock-out, internal soft-start, output under voltage protection, over voltage protection and thermal shutdown provide safe operation in all operating conditions.


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