RT6251A/B 3A, 18V, Synchronous Step-Down Converter General Description Features Low R Power MOSFET Switches 46m/36m DS(ON) The RT6251A/B is a high efficiency, monolithic Input Voltage Range : 4.5V to 18V synchronous step-down DC/DC converter that can deliver Adjustable Switching Frequency : 200kHz to 1.2MHz up to 3A output current from a 4.5V to 18V input supply. Current-Mode Control The RT6251A/B current-mode architecture with external Synchronous to External Clock : 200kHz to 1.2MHz compensation allows the transient response to be Accurate Voltage Reference 0.8V 1% optimized over a wide range of loads and output capacitors. Monotonic Start-Up into Pre-biased Outputs Cycle-by-cycle current limit provides protection against Adjustable Soft-Start shorted outputs and soft-start eliminates input current Power Good Indicator surge during start-up. Fault condition protections include Under-Voltage and Over-Voltage Protection output under-voltage protection, output over-voltage Input Under-Voltage Lockout protection, and over-temperature protection. The low current shutdown mode provides output disconnection, enabling easy power management in battery-powered Ordering Information systems. RT6251A/B Package Type QW : WQFN-14AL 3.5x3.5 (W-Type) Applications Lead Plating System High Performance Point of Load Regulation G : Green (Halogen Free and Pb Free) Notebook Computers H : Hiccup UVP N : Non-UVP High Density and Distributed Power Systems A : PSM B : PWM Note : Richtek products are : RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. Simplified Application Circuit RT6251A/B V VIN BOOT IN C IN C BOOT L PVIN LX V OUT Enable EN R1 FB C OUT PGOOD PGOOD R COMP1 R OSC COMP R2 RT/SYNC C C COMP2 COMP1 C SS SS/TR GND Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS6251A/B-00 November 2015 www.richtek.com 1RT6251A/B Marking Information Pin Configurations (TOP VIEW) RT6251AHGQW 0L= : Product Code YMDNN : Date Code 0L=YM DNN 1 14 2 13 GND BOOT 3 12 GND LX RT6251ANGQW 4 11 PVIN GND LX 0K= : Product Code PVIN 5 10 EN 15 6 9 VIN SS/TR YMDNN : Date Code 0K=YM 7 8 DNN WQFN-14AL 3.5x3.5 RT6251BHGQW 0J= : Product Code YMDNN : Date Code 0J=YM DNN RT6251BNGQW 0H= : Product Code YMDNN : Date Code 0H=YM DNN Functional Pin Description Pin No. Pin Name Pin Function Oscillator Resistor and External Frequency Synchronization Input. Connecting a 1 RT/SYNC resistor from this pin to GND sets the switching frequency or connecting an external clock to this pin changes the switching frequency. System Ground. Provide the ground return path for the control circuitry and 2, 3, GND low-side power MOSFET. The exposed pad must be soldered to a large PCB 15 (Exposed Pad) and connected to GND for minimum power dissipation. 4, 5 PVIN Power Input. Supplies the power switches of the device. Supply Voltage Input. Supplies the control circuitry and internal reference of the 6 VIN device. Feedback Voltage Input. This pin is used to set the desired output voltage via an 7 FB external resistive divider. The feedback reference voltage is 0.8V typically. Compensation Node. The current comparator threshold increases with this 8 COMP control voltage. Connect external compensation elements to this pin to stabilize the control loop. Soft-Start and Tracking Control Input. Connect a capacitor from SS to GND to 9 SS/TR set the soft-start period. The soft-start period can be used to track and sequence when the external voltage on this pin overrides the internal reference. Enable Control Input. Floating this pin or connecting this pin to logic high can 10 EN enable the device and connecting this pin to GND can disable the device. Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS6251A/B-00 November 2015 2 FB RT/SYNC COMP PGOOD