Datasheet LTC3887, LTC3887-1, LTC3887-2 (Analog Devices) - 10

LTC3887/LTC3887-1/ LTC3887-2
TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Load Current Power Loss vs Load Current Efficiency vs Load Current FSW = 350kHz (LTC3887) FSW = 350kHz (LTC3887) FSW = 500kHz (LTC3887)
95 8 95 12VIN 1.8VOUT 350kHz 12V 90 7 IN 1.5VOUT 350kHz 12V 90 IN 1.2VOUT 350kHz 6 12VIN 1.0VOUT 350kHz 85 85 5 80 80 4 75 75 EFFICIENCY (%) 3 POWER LOSS (W) EFFICIENCY (%) 70 70 12V 2 IN 1.8VOUT 350kHz 12VIN 1.8VOUT 500kHz 12V 12V 65 IN 1.5VOUT 350kHz IN 1.5VOUT 500kHz 12V 65 IN 1.2VOUT 350kHz 1 12VIN 1.2VOUT 500kHz 12VIN 1.0VOUT 350kHz 12VIN 1.0VOUT 500kHz 60 0 60 0 5 10 15 20 25 30 0 5 10 15 20 25 30 0 5 10 15 20 25 30 LOAD CURRENT (A) LOAD CURRENT (A) LOAD CURRENT (A) 3887 G01 3887 G02 3887 G03
Power Loss vs Load Current Load Step Load Step F (Forced Continuous Mode) (Pulse-Skipping Mode) SW = 500kHz (LTC3887)
8 12VIN 1.8VOUT 500kHz ILOAD ILOAD 7 12VIN 1.5VOUT 500kHz 5A/DIV 5A/DIV 12VIN 1.2VOUT 500kHz 6 12VIN 1.0VOUT 500kHz INDUCTOR INDUCTOR CURRENT CURRENT 5 5A/DIV 5A/DIV 4 VOUT VOUT 100mV/DIV 100mV/DIV 3 AC-COUPLED AC-COUPLED POWER LOSS (W) V 3887 G05 3887 G06 IN = 12V 50µs/DIV VIN = 12V 50µs/DIV 2 VOUT = 1.8V VOUT = 1.8V 0.3A TO 5A STEP 0.3A TO 5A STEP 1 0 0 5 10 15 20 25 30 LOAD CURRENT (A) 3887 G04
Inductor Current at Light Load Start-Up into a Prebiased Load Soft-Start Ramp
FORCED RUN RUN CONTINUOUS 2V/DIV 2V/DIV MODE 5A/DIV V V OUT OUT 1V/DIV 1V/DIV DISCONTINUOUS CONDUCTION MODE 5A/DIV t 3887 G08 3887 G09 RISE = 10ms 5ms/DIV tRISE = 10ms 5ms/DIV tDELAY = 5ms tDELAY = 5ms 3887 G07 1µs/DIV VIN = 12V VOUT = 1.8V ILOAD = 1A Rev.F 10 For more information www.analog.com Document Outline Features Applications Typical Application Description Table of Contents Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Overview Main Control Loop EEPROM (NVM) Power Up and Initialization Soft-Start Sequencing EVENT-Based Sequencing Shutdown Light Load Current Operation Switching Frequency and Phase Output Voltage Sensing Current Sensing PolyPhase Load Sharing External/Internal Temperature Sense RCONFIG (Resistor Configuration) Pins Fault Detection and Handling Internal EEPROM with CRC Protection and ECC Serial Interface Communication Protection Device Addressing Responses to VOUT and IOUT Faults Output Overvoltage Fault Response Output Undervoltage Response Peak Output Overcurrent Fault Response Responses to Timing Faults Responses to VIN OV Faults Responses to OT/UT Faults Internal Overtemperature Fault/Warn Response External Overtemperature and Undertemperature Fault Response Responses to External Faults Fault Logging Bus Timeout Protection Similarity Between PMBus, SMBus and I2C 2-Wire Interface PMBus Serial Digital Interface PMBus Command Summary PMBus Commands *Data Format Applications Information Current Limit Programming ISENSE+ and ISENSE– Pins Low Value Resistor Current Sensing Inductor DCR Current Sensing Slope Compensation and Inductor Peak Current Inductor Value Calculation Inductor Core Selection Power MOSFET and Schottky Diode (Optional) Selection Variable Delay Time, Soft-Start and Output Voltage Ramping Digital Servo Mode Soft Off (Sequenced Off) INTVCC Regulator Topside MOSFET Driver Supply (CB, DB) (LTC3887, LTC3887-2) Undervoltage Lockout CIN and COUT Selection Fault Conditions Open-Drain Pins Phase-Locked Loop and Frequency Synchronization Minimum On-Time Considerations RCONFIG (External Resistor Configuration Pins) Voltage Selection Frequency and Phase Selection Using RCONFIG Address Selection Using RCONFIG Efficiency Considerations Checking Transient Response PC Board Layout Checklist PC Board Layout Debugging Design Example Additional Design Checks Connecting the USB to the I2C/SMBus/PMBus Controller to the LTC3887 In System LTpowerPlay: An Interactive GUI for Digital Power PMBus Communication and Command Processing PMBus Command Details Addressing and Write Protect General Configuration Registers On/Off/Margin PWM Config Voltage Input Voltage and Limits Output Voltage and Limits Current Input Current Calibration Output Current Calibration Input Current Output Current Temperature External Temperature Calibration External Temperature Limits Timing Timing—On Sequence/Ramp Timing—Off Sequence/Ramp Precondition for Restart Fault Response Fault Responses All Faults Fault Responses Input Voltage Fault Responses Output Voltage Fault Responses Output Current Fault Responses IC Temperature Fault Responses External Temperature Fault Sharing Fault Sharing Propagation Fault Sharing Response Scratchpad Identification Fault Warning and Status Telemetry NVM (EEPROM) Memory Commands Store/Restore Fault Logging Block Memory Write/Read Typical Applications Package Description Revision History Typical Application Related Parts