SY21243RHC - High Efficiency Fast Response, 8A, 28V Input Synchronous Step Down Regulator


  • Low RDS(ON) for Internal Switches (Top/Bottom): 30/15mΩ
  • Wide Input Voltage Range: 4.5~24V
  • Integrated Bypass Switch: 1.2Ω
  • Instant PWM Architecture to Achieve Fast Transient Responses
  • Internal Soft-start Limits the Inrush Current
  • Pseudo-Constant Frequency: 500kHz
  • Adjustable Output Voltage Application
  • 8A 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: QFN2.5×2.5-16

Typical Application


The SY21243 develops a high efficiency synchronous step-down DC/DC regulator capable of delivering 8A current over a wide input voltage range of 4.5V to 24V.

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 30mΩ power and 15mΩ synchronous rectifier switches provide excellent efficiency over a range of applications, especially for low output voltages and low duty cycles. The SY21243 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 SY21243 is available in a compact QFN2.5×2.5-16 package.


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