Wide Range Input, Synchronous, Step-Down DC-to-DC Controller Data Sheet ADP1851 FEATURES TYPICAL OPERATION CIRCUIT V IN Input voltage range: 2.75 V to 20 V R RAMP Output voltage range: 0.6 V to 90% V IN RAMP VIN Maximum output current of more than 25 A M1 L DH Current mode architecture EN V BST OUT Configurable to voltage mode SW VCCO ILIM 1% output voltage accuracy over temperature FB Voltage tracking ADP1851 M2 DL SYNC Programmable frequency: 200 kHz to 1.5 MHz R HIGH CSG PGND Synchronization input FREQ LOW SS/TRK COMP Power saving mode at light load PGOOD Precision enable input AGND (EP) Power good with internal pull-up resistor Adjustable soft start Figure 1. Programmable current sense gain Integrated bootstrap diode Starts into a precharged load Externally adjustable slope compensation Suitable for any output capacitor Overvoltage and overcurrent-limit protection The ADP1851 provides a high speed, high peak current gate Thermal overload protection driving capability to enable energy efficient power conversion. Input undervoltage lockout (UVLO) The device can be configured to operate in power saving mode Available in 16-lead, 4 mm 4 mm LFCSP by skipping pulses, reducing switching losses, and improving Supported by ADIsimPower design tool efficiency at light load and standby conditions. The accurate current limit allows design within a narrower APPLICATIONS range of tolerances and can reduce overall converter size and Intermediate bus and POL systems requiring sequencing and cost. The ADP1851 can regulate down to 0.6 V output using a tracking, including high accuracy reference with 1% tolerance over the Telecom base station and networking temperature range of 40C to +125C. Industrial and instrumentation Medical and healthcare With its wide range input voltage, the ADP1851 provides the designer with maximum flexibility for use in a variety of system GENERAL DESCRIPTION configurations loop compensation, soft start, frequency setting, The ADP1851 is a wide range input, dc-to-dc, synchronous power saving mode, current limit, and current sense gain can buck controller capable of running from commonly used 3.3 V all be programmed using external components. In addition, the to 12 V (up to 20 V) voltage inputs. The device nominally external RAMP resistor allows the selection of optimal slope operates in current mode with valley current sensing providing and V feedforward in both current and voltage modes for IN the fastest step response for digital loads. It can also be config- excellent line rejection. The linear regulator and the bootstrap ured as a voltage mode controller with low noise and crosstalk diode for the high-side driver are internal. for sensitive loads. Protection features include undervoltage lockout, overvoltage, The ADP1851 is ideal in system applications requiring multiple overcurrent/short circuit, and overtemperature. output voltages. The ADP1851 includes a synchronization feature to eliminate beat frequencies between switching devices. It also provides accurate tracking capability between supplies and includes precision enable and power-good functions for simple, robust sequencing. Rev. B Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20122019 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 10595-001ADP1851 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Enable/Disable Control ............................................................. 14 Applications ....................................................................................... 1 Thermal Overload Protection .................................................. 14 General Description ......................................................................... 1 Applications Information .............................................................. 15 Typical Operation Circuit ................................................................ 1 ADIsimPower Design Tool ....................................................... 15 Revision History ............................................................................... 2 Setting the Output Voltage ........................................................ 15 Simplified Block Diagram ............................................................... 3 Soft Start ...................................................................................... 15 Specif icat ions ..................................................................................... 4 Setting the Current Limit .......................................................... 15 Absolute Maximum Ratings ............................................................ 6 Accurate Current-Limit Sensing .............................................. 15 ESD Caution .................................................................................. 6 Input Capacitor Selection .......................................................... 15 Pin Configuration and Function Descriptions ............................. 7 VIN Pin Filter ............................................................................. 16 Typical Performance Characteristics ............................................. 9 Boost Capacitor Selection ......................................................... 16 Theory of Operation ...................................................................... 11 Inductor Selection ...................................................................... 16 Control Architecture .................................................................. 11 Output Capacitor Selection ....................................................... 16 Oscillator Frequency .................................................................. 11 MOSFET Selection ..................................................................... 17 Synchronization .......................................................................... 12 Loop CompensationVoltage Mode ...................................... 18 PWM and Pulse Skip Modes of Operation ............................. 12 Loop CompensationCurrent Mode ..................................... 19 Synchronous Rectifier and Dead Time ................................... 13 Switching Noise and Overshoot Reduction ............................ 20 Input Undervoltage Lockout ..................................................... 13 Voltage Tracking ......................................................................... 21 Internal Linear Regulator .......................................................... 13 PCB Layout Guidelines .............................................................. 21 Overvoltage Protection .............................................................. 13 Typical Operating Circuits ............................................................ 22 Power Good ................................................................................. 13 Outline Dimensions ....................................................................... 23 Short-Circuit and Current-Limit Protection .......................... 14 Ordering Guide .......................................................................... 23 REVISION HISTORY 4/2019Rev. A to Rev. B Changes to Figure 24 ...................................................................... 15 2/2017Rev. 0 to Rev. A Updated Outline Dimensions ....................................................... 23 Change to Ordering Guide ............................................................ 23 8/2012Revision 0: Initial Version Rev. B Page 2 of 24