NR421A |Sanken Electric



Data Sheetdownload (PDF:1609.28KB)
Application Note


The NR421A is Synchronous Rectification buck regulator ICs integrates PowerMOSFETs. With the current mode control, low ESR capacitors such as ceramic capacitors can be used. It has achieved a high efficiency by the synchronous rectification system. The ICs have protection functions such as Over-Current Protection (OCP), Under-Voltage Lockout (UVLO) and Thermal Shutdown (TSD). Soft starting time can be set up by selecting an external capacitor value. The ON/OFF pin (EN Pin) turns the regulator ON/OFF. The NR421A is available in an 8-pin HSOP package with an exposed thermal pad on the back side.


・LCD TV / Blu-ray /Power supply for digital consumer
・Up to 94% efficiency Synchronous rectification system
・Current mode PWM control
・By the internal Phase Compensation, external component
  count reduction
・Stable with low ESR ceramic output capacitors


・For excellent heat dissipation, HSOP8 package with the
    heat-slug is adopted.
・Current mode PWM control
・Up to 94% efficiency
・Stable with low ESR ceramic output capacitors
・Built-in protection function
   Drooping type Over Current Protection (OCP) with Auto-
   Thermal Shutdown (TSD) with Auto-restart
   Under Voltage Lockout(UVLO)
・By the internal Phase Compensation, external component
    count reduction


*This product is not pin compatible with NR885E.
*This product is not a replacement product of NR885E.


Package Name:HSOP8

Package Diagram

Design Support

Calculation Tool for NR421A : Click here


Built-in PowerYES
Output Voltage0.8V to 14V
Output Current3A
Input Voltage Range4.5V to 18V
Operating Frequency350kHz
Current Mode ControlYES
Maximum Input Voltage18V
Minimum Input Voltage4.5V
Output on/offYES
Low ESR Capacitor SupportYES
Overcurrent ProtectionDrooping Type
Phase CompensationBuilt-in
Thermal ProtectionYES

Representative Circuit

Internal Block Diagram

Pin-Out Diagrams

Data Sheetdownload (PDF:1609.28KB)
Application Note
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