RT8288ZSP Richtek

RT8288 3A, 21V 500kHz Synchronous Step-Down Converter General Description Features zz z zz 3A Output Current The RT8288 is a synchronous step-down regulator with zz z zz Internal Soft-Start an internal power MOSFET. It achieves 3A of continuous zz z zz 120m/40m Internal Power MOSFET Switch output current over a wide input supply range with excellent zz z zz Internal Compensation Minimizes External Parts load and line regulation. Current mode operation provides Count fast transient response and eases loop stabilization. zz z zz Fixed 500kHz Frequency Fault condition protection includes cycle-by-cycle current zz z zz Thermal Shutdown Protection limiting and thermal shutdown. An internal soft-start zz z zz Cycle-by-Cycle Over Current Protection minimizes external parts count and internal compensation zz z zz Wide 4.5V to 21V Operating Input Range circuitry. zz z zz Adjustable Output from 0.808V to 15V The RT8288 requires a minimal number of readily available zz z zz Available in an SOP-8 (Exposed Pad) Package external components, providing a compact solution. zz z zz RoHS Compliant and Halogen Free Ordering Information Applications RT8288 z Distributive Power Systems Package Type z Battery Charger SP : SOP-8 (Exposed Pad-Option 2) z DSL Modems Lead Plating System z Pre-Regulator for Linear Regulators Z : ECO (Ecological Element with Halogen Free and Pb free) Note : Pin Configurations Richtek products are : (TOP VIEW) RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020. 8 VIN GND 2 7 SW Suitable for use in SnPb or Pb-free soldering processes. VCC GND 3 SW 6 FB 9 4 5 BOOT EN Marking Information SOP-8 (Exposed Pad) RT8288ZSP : Product Number RT8288 YMDNN : Date Code ZSPYMDNN Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8288-03 June 2012 www.richtek.com 1RT8288 Typical Application Circuit 4 1 V BOOT IN VIN C C BOOT IN RT8288 L 22F 100nF 2, 3 SW V OUT Chip Enable 6 5 EN FB R T R1 C R2 OUT 7 VCC 8, 9 (Exposed Pad) GND C C 0.1F Table 1. Recommended Components Selection V (V) R1 (k ) R2 (k ) R (k ) L ( H) C (F) OUT T OUT 5 75 14.46 0 4.7 22 x 2 3.3 75 24.32 0 3.6 22 x 2 2.5 75 35.82 0 3.6 22 x 2 1.8 5 4.07 30 2 22 x 2 1.5 5 5.84 39 2 22 x 2 1.2 5 10.31 47 2 22 x 2 1.05 5 16.69 47 1.5 22 x 2 Function Pin Description Pin No. Pin Name Pin Function Supply Input. VIN supplies the power to the IC, as well as the step-down converter 1 VIN switches. Drive VIN with a 4.5V to 21V power source. Bypass VIN to GND with a suitably large capacitor to eliminate noise on the input to the IC. Switch Node. SW is the switching node that supplies power to the output. Connect 2, 3 SW the output LC filter from SW to the output load. Note that a capacitor is required from SW to BOOT to power the high side switch. High Side Gate Drive Boost Input. BOOT supplies the drive for the high side 4 BOOT N-MOSFET switch. Connect a 100nF or greater capacitor from SW to BOOT to power the high side switch. Chip Enable (Active High). For automatic start-up, connect the EN pin to VIN with a 5 EN 100k resistor. Feedback Input. FB senses the output voltage to regulate said voltage. Drive FB 6 FB with a resistive voltage divider from the output voltage. The feedback threshold is 0.808V. Bias Supply. Decouple with 0.1 F to 0.22 F capacitor. The capacitance should be 7 VCC no more than 0.22 F. 8, Ground. The exposed pad must be soldered to a large PCB and connected to GND 9 (Exposed Pad) GND for maximum power dissipation. Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8288-03 June 2012 2