RT6278A/B TM 23V, 8A, 500kHz ACOT Synchronous Step-Down Converter General Description Features 8A Converter With Built-In 24m/12m Low R DS(ON) The RT6278A/B is a simple, easy-to-use, 8A synchronous Power FETs step-down DC-DC converter with an input supply voltage Input Supply Voltage Range : 4.5V to 23V range of 4.5V to 23V. The device build-in an accurate 0.6V Output Voltage Range : 0.6V to 5.1V reference voltage and integrates low R power DS(ON) TM Advanced Constant On-Time (ACOT ) Control MOSFETs to achieve high efficiency in a UQFN-12HL 3x3 Ultrafast Transient Response package. The RT6278A/B adopts Advanced Constant On- TM No Needs For External Compensations Time (ACOT ) control architecture to provide an ultrafast Optimized for Low-ESR Ceramic Output Capacitors transient response with few external components and to 0.6V 1% High-Accuracy Feedback Reference operate in nearly constant switching frequency over the Voltage line, load, and output voltage range. The RT6278A operates Optional for Operation Modes : in automatic PSM that maintains high efficiency during Power Saving Mode (PSM) (RT6278A) light load operation. The RT6278B operates in Forced Forced PWM Mode (RT6278B) PWM that helps meet tight voltage regulation accuracy Fixed Switching Frequency : 500kHz requirements. The RT6278A/B senses both FETs current Built-In Internally Fixed Soft-Start (Typ. 0.4ms) for a robust over-current protection. It features cycle-by- Input Under-Voltage Lockout (UVLO) cycle current limit protection and prevent the device from Output Under-Voltage Protection (UVP) with Hiccup the catastrophic damage in output short circuit, over current Mode or inductor saturation. A built-in soft-start function prevents Output Over-Voltage Protection (OVP) with Auto- inrush current during start-up. The device also includes Recovery Mode input under-voltage lockout, output under-voltage Ultrasonic Mode (USM) for RT6278A protection, over-voltage protection, and over-temperature Available In UQFN-12HL 3x3 (FC) (U-Type) Package protection (thermal shutdown) to provide safe and smooth operation in all operating conditions. The RT6278A/B is offered in a UQFN-12HL 3x3(FC) package. Ordering Information RT6278A/B Applications Package Type Industrial and Commercial Low Power Systems QUF : UQFN-12HL 3x3 (FC) (U-Type) Computer Peripherals Lead Plating System G : Green (Halogen Free and Pb Free) LCD Monitors and TVs Green Electronics/Appliances UVP Option Point of Load Regulation for High-Performance DSPs, H : Hiccup FPGAs, and ASICs PWM Operation Mode Networking Communication A : Automatic PSM B: Forced 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. Copyright 2017 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS6278A/B-00 October 2017 www.richtek.com 1RT6278A/B Pin Configuration Marking Information (TOP VIEW) RT6278AHGQUF M8= : Product Code YMDNN : Date Code M8=YM DNN 12 11 10 9 8 7 BOOT 1 6 EN 5 VIN LX 2 RT6278BHGQUF 4 PGND M7= : Product Code LX 3 YMDNN : Date Code M7=YM UQFN-12HL 3x3 DNN Functional Pin Description Pin No. Pin Name Pin Function Boot-strap pin. Supply high-side gate driver. Decouple this pin to LX pin with 1 BOOT 0.1F ceramic cap. 2, 3 LX Inductor pin. Connect this pin to the switching node of inductor. 4 PGND Power ground. 5 VIN Input pin. Decouple this pin to GND pin with at least 10F ceramic cap. Enable control. Pull this pin high to turn on the Buck. Do not leave this pin floating. EN pin will also be used to set USM mode for RT6278A, when EN 6 EN pin voltage is between 2.3V and 23V, it will enter USM mode, if EN pin voltage is between 0.8V and 1.7V, then it is normal mode. Power good indicator. Open drain output when the output voltage is within 7 PGOOD 90% to 120% of regulation point. 8 AGND Analog ground. 5V linear regulator output for internal control circuit. A capacitor (typical 1F) 9 VCC should be connected to AGND. Dont connect to external Load. Output feedback pin. Connect this pin to the center point of the output 10 FB resistor divider to program the output voltage. Bypass input for the internal LDO. BYP is externally connected to the output of switching regulator. When the BYP voltage rises above the bypass switch 11 BYP turn-on threshold, the LDO regulator shuts down and the VCC pin is connected to the BYP pin through an internal switch. Current limit setting pin. The current limit is set to 8A, 10A or 12A when this 12 ILMT pin is pull low, floating or pull high respectively. Copyright 2017 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS6278A/B-00 October 2017 2 ILMT BYP FB VCC AGND PGOOD