LTC3880/LTC3880-1
TABLE OF CONTENTS
Features...................................................... 1
Applications................................................. 1
Typical Application......................................... 1
Description.................................................. 1
Table of Contents........................................... 2
Absolute Maximum Ratings............................... 4
Pin Configuration........................................... 4
Order Information........................................... 4
Electrical Characteristics.................................. 5
Typical Performance Characteristics................... 11
Pin Functions............................................... 15
Block Diagram.............................................. 17
Operation................................................... 18
Overview.................................................................. 18
Main Control Loop................................................... 18
EEPROM.................................................................. 19
Power Up and Initialization......................................20
Soft-Start................................................................. 20
Sequencing.............................................................. 21
Voltage-Based Sequencing...................................... 21
Shutdown................................................................ 21
Light Load Current Operation..................................22
Switching Frequency and Phase..............................22
Output Voltage Sensing...........................................23
Current Sensing.......................................................23
Load Sharing........................................................... 24
External/Internal Temperature Sense....................... 24
RCONFIG (Resistor Configuration) Pins...................25
Fault Detection and Handling................................... 25
Internal Memory with CRC and ECC....................26
Serial Interface........................................................ 27
Communication Failure ....................................... 27
Device Addressing................................................... 27
Responses to VOUT and IOUT Faults......................... 28
Output Overvoltage Fault Response.................... 28
Output Undervoltage Response .......................... 28
Peak Output Overcurrent Fault Response............ 28
Responses to Timing Faults.....................................29
Responses to VIN OV Faults.....................................29
Responses to OT/UT Faults......................................29
Overtemperature Fault Response—Internal .......29
Overtemperature and Undertemperature
Fault Response—Externals ................................29
Responses to External Faults ..................................29
Bus Timeout Failure.................................................30
Similarity Between PMBus, SMBus and I2C
2-Wire Interface.......................................................30
PMBus Serial Digital Interface................................. 31
PMBus Command Summary............................. 34
PMBus Commands..................................................34
*Data Format...........................................................39
Applications Information................................. 40
Current Limit Programming.....................................40
ISENSE+ and ISENSE– Pins..........................................40
Low Value Resistor Current Sensing........................ 41
Inductor DCR Current Sensing................................. 42
Slope Compensation and Inductor Peak Current.....43
Inductor Value Calculation.......................................43
Inductor Core Selection...........................................44
Power MOSFET and Schottky Diode (Optional)
Selection.................................................................. 44
Variable Delay Time, Soft-Start and Output Voltage
Ramping.................................................................. 45
Digital Servo Mode..................................................46
Soft Off (Sequenced Off).........................................46
INTVCC Regulator..................................................... 47
Topside MOSFET Driver Supply (CB, DB).................48
Undervoltage Lockout..............................................48
CIN and COUT Selection............................................48
Fault Conditions....................................................... 49
Open-Drain Pins......................................................50
Phase-Locked Loop and Frequency
Synchronization....................................................... 50
Minimum On-Time Considerations.......................... 51
Rev. H
2
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