Datasheet LTC3884, LTC3884-1 (Analog Devices) - 79

LTC3884/LTC3884-1
PMBus COMMAND DETAILS
For both equations, G = MFR_TEMP_1_GAIN • 2–14, and O = MFR_TEMP_1_OFFSET Bit[2] determines if the part uses sub-milliohm DCR for sensing the output current. This is a very critical selection in terms of overcurrent limit. It is highly recommend that Bit[2] should not be changed when device is in operation. Bit[1] of this command determines if the part is in high range or low voltage range. Changing this bit value changes the PWM loop gain and compensation. This bit value should not be changed when the channel output is active. Writing this bit when the channel is active will generate a CML fault. Bit[0] determines if the PWM mode of operation is discontinuous (pulse-skipping mode), or forced continuous con- duction mode. Whenever the channel is ramping on, the PWM mode will be discontinuous, regardless of the value of this bit. This command has one data byte.
MFR_PWM_COMP
The MFR_PWM_COMP command sets the gm of the PWM channel error amplifiers and the value of the internal RITHn compensation resistors. This command affects the loop gain of the PWM output which may require modifications to the external compensation network.
BIT MEANING BIT [7:5] Error Amplifier GM Adjust (mS)
000b 1.00 001b 1.68 010b 2.35 011b 3.02 100b 3.69 101b 4.36 110b 5.04 111b 5.73
BIT [4:0] RITH (k
Ω
)
00000b 0 00001b 0.25 00010b 0.5 00011b 0.75 00100b 1 00101b 1.25 00110b 1.5 00111b 1.75 01000b 2 01001b 2.5 01010b 3 01011b 3.5 01100b 4 01101b 4.5 01110b 5 Rev. F For more information www.analog.com 79 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 Power-Up and Initialization Soft-Start Time-Based Sequencing Voltage-Based Sequencing Shutdown Light-Load Current Operation Switching Frequency and Phase PWM Loop Compensation Output Voltage Sensing INTVCC/EXTVCC Power Output Current Sensing and Sub Milliohm DCR Current Sensing Input Current Sensing PolyPhase Load Sharing External/Internal Temperature Sense RCONFIG (Resistor Configuration) Pins Fault Detection and Handling Status Registers and ALERT Masking Mapping Faults to FAULT Pins Power Good Pins CRC Protection and ECC Serial Interface Communication Protection Device Addressing Responses to VOUT, IIN 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 Response External Overtemperature and Undertemperature Fault Response Responses to Input Overcurrent and Output Undercurrent Faults 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 ISENSE0± and ISENSE1± Pins Inductor DCR Sensing Inductor Value Calculation Inductor Core Selection Low Value Resistor Current Sensing Slope Compensation and Inductor Peak Current Power MOSFET and Optional Schottky Diode Selection Variable Delay Time, Soft-Start and Output Voltage Ramping Digital Servo Mode Soft Off (Sequenced Off) INTVCC/EXTVCC Power Topside MOSFET Driver Supply (CB, DB) Undervoltage Lockout CIN and COUT Selection Fault Indication Open-Drain Pins Phase-Locked Loop and Frequency Synchronization Minimum On-Time Considerations External Temperature Sense Input Current Sense Amplifier External Resistor Configuration Pins (RCONFIG) Voltage Selection Frequency Selection Phase Selection Address Selection Using RCONFIG Efficiency Considerations Programmable Loop Compensation Checking Transient Response PolyPhase Configuration Master Slave Operation PC Board Layout Checklist PC Board Layout Debugging Design Example Additional Design Checks Connecting the USB to I2C/SMBus/PMBus Controller to the LTC3884 in System LTpowerPlay: An Interactive GUI for Digital Power PMBus Communication and Command Processing PMBus Command Details Addressing and Write Protect General Configuration Commands On/Off/Margin PWM Configuration Voltage Input Voltage and Limits Output Voltage and Limits Output Current and Limits Input Current and Limits Temperature External Temperature Calibration 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 Memory Commands Store/Restore Fault Log Operation Fault Logging Block Memory Write/Read Typical Applications Package Description Revision History Typical Application Related Parts