SY21240RAC - 9A Continuous/14A Peak, 28V Input, Synchronous Step Down Regulator with ±1A VTT LDO and ±10mA Buffered Reference


  • Low RDS(ON) for Internal Switches of the Regulator (Top/Bottom): 27/9mΩ
  • 4~24V Input Voltage Range
  • Instant PWM Architecture to Achieve Fast Transient Responses
  • Internal 450µs Soft-start Limits the Inrush Current
  • 600kHz Pseudo-Constant Switching Frequency
  • PFM/USM Selectable Light Load Operation Mode
  • Power Good Indicator
  • 9A Continuous/14A Peak Output Current Capability of the Regulator
  • ±1% 0.6V Reference
  • ±1A Source/Sink Current Capability of the VTT LDO
  • Buffered Low Noise ±10mA VTTREF Output
  • Support VTT LDO High-Z in S3
  • Output Tracking Discharge Function for the Regulator and VTT LDO
  • Cycle-by-cycle Valley and Peak Current Limit Protection
  • Latch-off Mode Output Under Voltage Protection
  • Latch-off Mode Output Over Voltage Protection
  • Latch-off Mode Over Temperature Protection
  • Input UVLO and Bias UVLO
  • RoHS Compliant and Halogen Free
  • Compact Package: QFN3×3-20

Typical Application


The SY21240 provides a complete power supply with the highest density for DDR3, DDR3L, LPDDR3 and DDR4 memory. It develops one high efficiency synchronous step-down DC/DC regulator capable of delivering 9A continuous/14A peak current and one sink/source VTT LDO capable of delivering ±1A current. In addition, it operates at 600kHz pseudo-constant frequency under continuous conduction mode. The integrated low RDS(ON) switches minimize the conduction loss.

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 SY21240 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 and 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