RT2859A/B TM 3A, 18V, 650kHz, ACOT Synchronous Step-Down Converter General Description The RT2859A/B are high-performance 650kHz 3A step- to avoid low-frequency interference while the RT2859A down regulators with internal power switches and features a power-saving discontinuous operating mode at synchronous rectifiers. They feature quick transient light loads. response using their Advanced Constant On-Time TM (ACOT ) control architecture that provides stable Features operation with small ceramic output capacitors and without Fast Transient Response complicated external compensation, among other benefits. Steady 650kHz Switching Frequency The input voltage range is from 4.5V to 18V and the output At all Load Current (RT2859B) is adjustable from 0.765V to 7V. Discontinuous Operating Mode at Light Load TM (RT2859A) The proprietary ACOT control improves upon other fast- 3A Output Current response constant on-time architectures, achieving nearly TM Advanced Constant On-Time (ACOT ) Control constant switching frequency over line, load, and output Optimized for Ceramic Output Capacitors voltage ranges. Since there is no internal clock, response 4.5V to 18V Input Voltage Range to transients is nearly instantaneous and inductor current Internal 70m Switch and 70m Synchronous can ramp quickly to maintain output regulation without Rectifier large bulk output capacitance. The RT2859A/B are stable 0.765V to 7V Adjustable Output Voltage with and optimized for ceramic output capacitors Externally-adjustable, Pre-biased Compatible Soft- With internal 70m switches and 70m synchronous Start rectifiers, the RT2859A/B display excellent efficiency and Cycle-by-Cycle Current Limit good behavior across a range of applications, especially Optional Output Discharge Function for low output voltages and low duty cycles. Cycle-by- Output Over- and Under-voltage Shut Down cycle current limit, input under-voltage lockout, externally- Latched (RT2859ALGQW/RT2859BLGQW Only) adjustable soft-start, output under- and over-voltage With Hiccup Mode (RT2859AHGQW/RT2859BHGQW protection, and thermal shutdown provide safe and smooth Only) operation in all operating conditions. Input Under-Voltage Lockout The RT2859A and RT2859B are each available in Thermal Shutdown the WQFN-16L 3x3 package, with exposed thermal pads. RoHS Compliant and Halogen Free The RT2859B switches continuously even at light loads Simplified Application Circuit RT2859A/B V VIN V IN SW OUT VCC BOOT Power Good VS PGOOD VREG5 FB Input Signal EN SS VREG5 GND PGND Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS2859A/B-00 February 2014 www.richtek.com 1RT2859A/B Applications Ordering Information RT2859A/B Industrial and Commercial Low Power Systems Computer Peripherals Package Type QW : WQFN-16L 3x3 (W-Type) LCD Monitors and TVs Green Electronics/Appliances Lead Plating System G : Green (Halogen Free and Pb Free) Point of Load Regulation for High-Performance DSPs, FPGAs, and ASICs H : Hiccup Mode OVP & UVP L : Latched OVP & UVP A : PSM Marking Information B : PWM RT2859AHGQW Note : 48= : Product Code Richtek products are : YMDNN : Date Code 48=YM RoHS compliant and compatible with the current require- DNN ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. RT2859ALGQW 45= : Product Code Pin Configurations YMDNN : Date Code 45=YM (TOP VIEW) DNN 16 15 14 13 1 12 FB BOOT RT2859BHGQW VREG5 2 11 SW GND 3Z= : Product Code 3 10 SS SW 17 YMDNN : Date Code 4 9 GND SW 3Z=YM 5 6 7 8 DNN RT2859BLGQW WQFN-16L 3x3 3Y= : Product Code YMDNN : Date Code 3Y=YM DNN Copyright 2014 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS2859A/B-00 February 2014 2 PGOOD VS EN VCC PGND VIN PGND VIN