RT7251A/B 1.5A, 17V, 340/800kHz Synchronous Step-Down Converter General Description Features zz z zz 4V to 17V Input Voltage Range The RT7251A/B is a high efficiency, monolithic zz z zz 1.5A Output Current synchronous step-down DC/DC converter that can operate zz z zz Internal N-MOSFETs at 340kHz/800kHz, while delivering up to 1.5A output zz z zz Current Mode Control current from a 4V to 17V input supply. The RT7251A/B s zz z zz Fixed Frequency Operation : 340kHz/800kHz current mode architecture allows the transient response zz z zz Output Adjustable from 0.8V to 12V to be optimized. Cycle-by-cycle current limit provides zz z zz Up to 95% Efficiency protection against shorted outputs and soft-start eliminates zz z zz Internal Compensation input current surge during start-up. Fault conditions also zz z zz Stable with Low ESR Ceramic Output Capacitors include output under voltage protection, output over voltage zz z zz Cycle-by-Cycle Over Current Protection protection and thermal shutdown. The low current (<5A) zz z zz Input Under Voltage Lockout shutdown mode provides output disconnection, enabling zz z zz Output Under Voltage Protection easy power management in battery-powered systems. The zz z zz Output Over Voltage Protection RT7251A/B is available in a WDFN-8L 2x2 package. zz z zz Power Good Indicator zz z zz Thermal Shutdown Protection Ordering Information zz z zz RoHS Compliant and Halogen Free RT7251A/B Package Type Applications QW : WDFN-8L 2x2 (W-Type) zz z zz Industrial and Commercial Low Power Systems Lead Plating System Z : ECO (Ecological Element with zz z zz Computer Peripherals Halogen Free and Pb free) zz z zz LCD Monitors and TVs A : 340kHz zz z zz Green Electronics/Appliances B : 800kHz zz z zz Point of Load Regulation for High-Performance DSPs, Note : FPGAs, and ASICs Richtek products are : RoHS compliant and compatible with the current require- Pin Configurations ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. (TOP VIEW) 1 8 SW GND 2 7 VIN GND Marking Information 3 6 BOOT PGOOD 9 EN 4 5 FB RT7251AZQW 03 : Product Code WDFN-8L 2x2 W : Date Code 03W RT7251BZQW 70 : Product Code W : Date Code 70W Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS7251A/B-01 April 2012 www.richtek.com 1 GNDRT7251A/B Typical Application Circuit RT7251A V IN 2 3 VIN BOOT 4V to 17V C IN C BOOT L 10F 10nF 15H V OUT 1 SW 3.3V 6 PGOOD PGOOD 1.5A R1 110k 5 Chip Enable FB 4 EN C OUT R2 22F x 2 36k 7, 8, 9 (Exposed Pad) GND RT7251B V IN 2 3 VIN BOOT 4V to 17V C IN C BOOT L 10F 10nF 6.8H V OUT 1 SW 3.3V 6 PGOOD PGOOD 1.5A R1 47k 5 Chip Enable FB 4 EN C OUT R2 22F x 2 15k 7, 8, 9 (Exposed Pad) GND Table 1. Recommended Component Selection RT7251A V (V) L (H) R1 (k) R2 (k) C (F) OUT OUT 1.2 4.7 110 220 22 x 2 2.5 10 110 51 22 x 2 3.3 15 110 36 22 x 2 5 22 120 22 22 x 2 RT7251B V (V) L (H) R1 (k) R2 (k) C (F) OUT OUT 1.2 3.6 47 91 22 x 2 2.5 4.7 47 22 22 x 2 3.3 6.8 47 15 22 x 2 5 10 62 12 22 x 2 Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS7251A/B-01 April 2012 2