Dual Output Synchronous Buck PWM Controller Data Sheet ADP1877 ranges from 200 kHz to 1.5 MHz. The ADP1877 provides an FEATURES output voltage accuracy of 0.85% from 40C to +85C and Input voltage range: 2.75 V to 14.5 V 1.5% from 40C to 125C in junction temperature. This part Output voltage range: 0.6 V to 90% V IN can be powered from a 2.75 V to 14.5 V supply, operates over Maximum output current greater than 25 A per channel o o the 40 C to +125 C junction temperature range, and is availa- Programmable frequency: 200 kHz to 1.5 MHz ble in a 32-lead 5 mm 5 mm LFCSP package. Flex-Mode architecture with integrated drivers 180 phase shift minimizes input ripple current and required input capacitance VIN R AMP1 0.85% output voltage accuracy 40C to +85C Integrated boost diodes RAMP1 VIN Pulse skip high efficiency mode under light load M1 EN1 L1 DH1 Power good with internal pull-up resistor EN2 BST1 VDL VOUT1 Overvoltage and overcurrent limit protection SW1 R TOP1 ILIM1 Thermal overload protection VCCO FB1 PGOOD1 Input undervoltage lockout (UVLO) PGOOD2 M2 DL1 R Externally adjustable soft start, slope compensation and BOT1 TRK1 R TRK2 CSG1 current sense gain PGND1 SYNC Independent precision enable inputs R RAMP2 FREQ VIN RAMP2 Synchronization input Suitable for any output capacitors M3 COMP1 L2 DH2 Available in 32-lead 5 mm 5 mm LFCSP BST2 COMP2 VOUT2 SW2 R APPLICATIONS TOP2 ILIM2 FB2 Set top boxes SS1 M4 SS2 DL2 Printers R BOT2 R CSG2 Communication infrastructure AGND PGND2 Distributor power dc systems Industrial and instrumentation Figure 1. Typical Operation Circuit GENERAL DESCRIPTION 100 V = 3.3V PSM O 90 The ADP1877 is a Flex-Mode (proprietary architecture of Analog Devices, Inc.), dual-channel, step-down switching 80 V = 1.8V PSM O controller with integrated drivers that drive N-channel 70 synchronous power MOSFETs. The two PWM outputs are V = 3.3V PWM O 60 phase shifted 180, which reduces the input RMS current, thus 50 minimizing required input capacitance. V = 1.8V PWM O 40 The boost diodes are built into the ADP1877, thus lowering the 30 overall system cost and component count. The ADP1877 can 20 be set to operate in pulse skip high efficiency mode under light load or in PWM continuous conduction mode. 10 V = 12V, 300kHz IN 0 The ADP1877 includes externally adjustable soft start, output 0.01 0.1 1 10 100 overvoltage protection, externally adjustable current limit, LOAD (A) power good, and a programmable oscillator frequency that Figure 2. Efficiency Plot of Figure 42, 20 A Output Rev. 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EFFICIENCY (%) 08299-002 08299-001ADP1877 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Setting the Current Limit .......................................................... 17 Applications ....................................................................................... 1 Accurate Current-Limit Sensing .............................................. 18 General Description ......................................................................... 1 Setting the Slope Compensation .............................................. 18 Revision History ............................................................................... 2 Setting the Current Sense Gain ................................................ 18 Specif icat ions ..................................................................................... 3 Input Capacitor Selection .......................................................... 19 Absolute Maximum Ratings ............................................................ 6 Input Filter ................................................................................... 19 ESD Caution .................................................................................. 6 Boost Capacitor Selection ......................................................... 20 Simplified Block Diagram ............................................................... 7 Inductor Selection ...................................................................... 20 Pin Configuration and Function Descriptions ............................. 8 Output Capacitor Selection ....................................................... 20 Typical Performance Characteristics ........................................... 10 MOSFET Selection ..................................................................... 21 Theory of Operation ...................................................................... 13 Loop Compensation .................................................................. 22 Control Architecture .................................................................. 13 Switching Noise and Overshoot Reduction ............................ 23 Oscillator Frequency .................................................................. 13 Voltage Tracking ......................................................................... 23 Mode of Operation ..................................................................... 14 Coincident Tracking .................................................................. 23 Synchronization .......................................................................... 14 Ratiometric Tracking ................................................................. 24 Soft Start ...................................................................................... 14 PCB Layout Guideline ................................................................... 25 Synchronous Rectifier and Dead Time ................................... 15 MOSFETs, Input Bulk Capacitor, and Bypass Capacitor ...... 25 Input Undervoltage Lockout ..................................................... 15 High Current and Current Sense Paths ................................... 25 Internal Linear Regulator .......................................................... 15 Signal Paths ................................................................................. 25 Overvoltage Protection .............................................................. 15 PGND Plane ................................................................................ 25 Power Good ................................................................................. 15 Feedback and Current-Limit Sense Paths ............................... 25 Short-Circuit and Current-Limit Protection .......................... 16 Switch Node ................................................................................ 26 Shutdown Control ...................................................................... 16 Gate Driver Paths ....................................................................... 26 Thermal Overload Protection ................................................... 16 Output Capacitors ...................................................................... 26 Applications Information .............................................................. 17 Typical Operating Circuits ............................................................ 27 Setting the Output Voltage ........................................................ 17 Outline Dimensions ....................................................................... 31 Soft Start ...................................................................................... 17 Ordering Guide .......................................................................... 31 REVISION HISTORY 4/12Rev. C to Rev. D 9/09Rev. 0 to Rev. A Changes to Setting the Current Sense Gain Section .................. 18 Changes to Features Section, General Description Section, and Updated Outline Dimensions ....................................................... 31 Figure 2 ............................................................................................... 1 Changes to Output Characteristics, Feedback Accuracy Voltage 4/10Rev. B to Rev. C Parameter Error Amplifier, Transconductance Parameter and Changes to Features and General Description ............................. 1 Linear Regulator, VCCO Load Regulation and VIN to VCCO Changes to Quiescent Current Parameter and FB to TRK Offset Dropout Voltage Parameters, Table 1 ............................................. 3 Voltage Parameter, Table 1 .............................................................. 3 Changes to Pin 4, Pin 16, and Pin 25 Descriptions, Table 3 ........ 8 Changes to Theory of Operation Section .................................... 13 Changes to Figure 5 and Figure 6 ................................................. 10 Changes to Setting the Slope Compensation Section ................ 18 9/09Revision 0: Initial Version 11/09Rev. A to Rev. B Changes to Product Title ................................................................. 1 Changes to Signal Path Section .................................................... 25 Rev. D Page 2 of 32