Datasheet LT8708-1 (Analog Devices) - 5
| Manufacturer | Analog Devices |
| Description | 80V Synchronous 4-Switch Buck-Boost DC/DC Slave Controller for LT8708 Multiphase System |
| Pages / Page | 36 / 5 — ELECTRICAL CHARACTERISTICS. The. denotes the specifications which apply … |
| Revision | A |
| File Format / Size | PDF / 2.0 Mb |
| Document Language | English |
ELECTRICAL CHARACTERISTICS. The. denotes the specifications which apply over the specified operating
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LT8708-1
ELECTRICAL CHARACTERISTICS The
l
denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C. VINCHIP =12V, SHDN = 3V, DIR = 3.3V unless otherwise noted. (Note 3). PARAMETER CONDITIONS MIN TYP MAX UNITS
MODE Pin Continuous Conduction Mode (CCM) Threshold l 0.4 V MODE Pin Hybrid DCM/CCM Mode (HCM) Range l 0.8 1.2 V MODE Pin Discontinuous Conduction Mode (DCM) Range l 1.6 2.0 V MODE Pin Burst Mode Operation Threshold l 2.4 V DIR Pin Forward Operation Threshold l 1.6 V DIR Pin Reverse Operation Threshold l 1.2 V RVSOFF Output Voltage Low IRVSOFF = 200µA l 0.08 0.5 V RVSOFF Falling Threshold Voltage l 1.155 1.209 1.275 V RVSOFF Threshold Voltage Hysteresis 165 mV Soft-Start Charging Current VSS = 0V 13 19 25 µA VSS = 0.5V 21 31 41 µA IMON_ON Rising Threshold for FDCM Operation MODE = 1V (HCM), DIR = 3.3V l 235 255 280 mV IMON_ON Falling Threshold for CCM Operation MODE = 1V (HCM), DIR = 3.3V l 185 205 235 mV IMON_INP Rising Threshold for RDCM Operation MODE = 1V (HCM), DIR = 0V l 235 255 280 mV IMON_INP Falling Threshold for CCM Operation MODE = 1V (HCM), DIR = 0V l 185 205 235 mV ICP Rising Threshold for Start Switching l 485 510 536 mV ICN Rising Threshold for Start Switching l 485 510 536 mV ICP Rising Threshold for Enabling Non-CCM Offset Current l 680 704 730 mV ICP Falling Threshold for Disabling Non-CCM Offset Current l 500 530 560 mV ICN Rising Threshold for Enabling Non-CCM Offset Current l 680 704 730 mV ICN Falling Threshold for Disabling Non-CCM Offset Current l 500 530 560 mV
Voltage Regulation Loops (Refer to Block Diagram to Locate Amplifiers)
Regulation Voltage for FBOUT Regulate VC to 1.2V l 1.193 1.207 1.222 V Regulation Voltage for FBIN Regulate VC to 1.2V l 1.184 1.205 1.226 V Line Regulation for FBOUT and FBIN Error Amp Reference Voltage VINCHIP = 12V to 80V, Not Switching 0.002 0.005 %/V FBOUT Pin Bias Current Current Out of Pin 15 nA FBOUT Error Amp EA4 gm 345 µmho FBOUT Error Amp EA4 Voltage Gain 245 V/V VOUTLOMON Voltage Activation Threshold Falling l 1.185 1.207 1.225 V VOUTLOMON Threshold Voltage Hysteresis 24 mV VOUTLOMON Pin Bias Current VVOUTLOMON = 1.24V, Current Into Pin 0.01 µA VVOUTLOMON = 1.17V, Current Into Pin l 0.8 1 1.2 µA FBIN Pin Bias Current Current Out of Pin 10 nA FBIN Error Amp EA3 gm 235 µmho FBIN Error Amp EA3 Voltage Gain 150 V/V VINHIMON Voltage Activation Threshold Rising l 1.185 1.207 1.23 V VINHIMON Threshold Voltage Hysteresis 24 mV VINHIMON Pin Bias Current VVINHIMON = 1.17V, Current Into Pin 0.01 µA VVINHIMON = 1.24V, Current Out of Pin l 0.8 1 1.2 µA Rev 0 For more information www.analog.com 5 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Typical Application Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Common LT8708-1 and LT8708 Features Adding Phases to an LT8708 Application Adding Phases: The Master LT8708 Adding Phases: The Slave LT8708-1 Start-Up Start-Up: SWEN Pin Start-Up: Soft-Start of Switching Regulator Control Overview Power Switch Control Unidirectional and Bidirectional Conduction Error Amplifiers Transfer Function: IOUT(SLAVE) Vs IOUT(MASTER) Transfer Function: CCM Transfer Function: DCM, HCM and Burst Mode Operation Current Monitoring and Limiting Monitoring: IOUT(SLAVE) Monitoring and Limiting: IIN(SLAVE) Multiphase Clocking Applications Information Quick-Start Multiphase Setup Quick Setup: Design the Master Phase Quick Setup: Design the Slave Phase(s) Quick Setup: Evaluation Choosing the Total Number of Phases Operating Frequency Selection CIN and COUT Selection CIN and COUT Selection: VIN Capacitance CIN and COUT Selection: VOUT Capacitance VINHIMON, VOUTLOMON and RVSOFF Configuring the IIN(SLAVE) Current Limits Regulating IOUT(SLAVE) IOUT(SLAVE): Circuit Description IOUT(SLAVE): Configuration Loop Compensation Voltage Lockouts Circuit Board Layout Checklist Design Example Typical Applications Package Description Typical Application Related Parts
ELECTRICAL CHARACTERISTICS The
l
denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C. VINCHIP =12V, SHDN = 3V, DIR = 3.3V unless otherwise noted. (Note 3). PARAMETER CONDITIONS MIN TYP MAX UNITS
MODE Pin Continuous Conduction Mode (CCM) Threshold l 0.4 V MODE Pin Hybrid DCM/CCM Mode (HCM) Range l 0.8 1.2 V MODE Pin Discontinuous Conduction Mode (DCM) Range l 1.6 2.0 V MODE Pin Burst Mode Operation Threshold l 2.4 V DIR Pin Forward Operation Threshold l 1.6 V DIR Pin Reverse Operation Threshold l 1.2 V RVSOFF Output Voltage Low IRVSOFF = 200µA l 0.08 0.5 V RVSOFF Falling Threshold Voltage l 1.155 1.209 1.275 V RVSOFF Threshold Voltage Hysteresis 165 mV Soft-Start Charging Current VSS = 0V 13 19 25 µA VSS = 0.5V 21 31 41 µA IMON_ON Rising Threshold for FDCM Operation MODE = 1V (HCM), DIR = 3.3V l 235 255 280 mV IMON_ON Falling Threshold for CCM Operation MODE = 1V (HCM), DIR = 3.3V l 185 205 235 mV IMON_INP Rising Threshold for RDCM Operation MODE = 1V (HCM), DIR = 0V l 235 255 280 mV IMON_INP Falling Threshold for CCM Operation MODE = 1V (HCM), DIR = 0V l 185 205 235 mV ICP Rising Threshold for Start Switching l 485 510 536 mV ICN Rising Threshold for Start Switching l 485 510 536 mV ICP Rising Threshold for Enabling Non-CCM Offset Current l 680 704 730 mV ICP Falling Threshold for Disabling Non-CCM Offset Current l 500 530 560 mV ICN Rising Threshold for Enabling Non-CCM Offset Current l 680 704 730 mV ICN Falling Threshold for Disabling Non-CCM Offset Current l 500 530 560 mV
Voltage Regulation Loops (Refer to Block Diagram to Locate Amplifiers)
Regulation Voltage for FBOUT Regulate VC to 1.2V l 1.193 1.207 1.222 V Regulation Voltage for FBIN Regulate VC to 1.2V l 1.184 1.205 1.226 V Line Regulation for FBOUT and FBIN Error Amp Reference Voltage VINCHIP = 12V to 80V, Not Switching 0.002 0.005 %/V FBOUT Pin Bias Current Current Out of Pin 15 nA FBOUT Error Amp EA4 gm 345 µmho FBOUT Error Amp EA4 Voltage Gain 245 V/V VOUTLOMON Voltage Activation Threshold Falling l 1.185 1.207 1.225 V VOUTLOMON Threshold Voltage Hysteresis 24 mV VOUTLOMON Pin Bias Current VVOUTLOMON = 1.24V, Current Into Pin 0.01 µA VVOUTLOMON = 1.17V, Current Into Pin l 0.8 1 1.2 µA FBIN Pin Bias Current Current Out of Pin 10 nA FBIN Error Amp EA3 gm 235 µmho FBIN Error Amp EA3 Voltage Gain 150 V/V VINHIMON Voltage Activation Threshold Rising l 1.185 1.207 1.23 V VINHIMON Threshold Voltage Hysteresis 24 mV VINHIMON Pin Bias Current VVINHIMON = 1.17V, Current Into Pin 0.01 µA VVINHIMON = 1.24V, Current Out of Pin l 0.8 1 1.2 µA Rev 0 For more information www.analog.com 5 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Typical Application Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Common LT8708-1 and LT8708 Features Adding Phases to an LT8708 Application Adding Phases: The Master LT8708 Adding Phases: The Slave LT8708-1 Start-Up Start-Up: SWEN Pin Start-Up: Soft-Start of Switching Regulator Control Overview Power Switch Control Unidirectional and Bidirectional Conduction Error Amplifiers Transfer Function: IOUT(SLAVE) Vs IOUT(MASTER) Transfer Function: CCM Transfer Function: DCM, HCM and Burst Mode Operation Current Monitoring and Limiting Monitoring: IOUT(SLAVE) Monitoring and Limiting: IIN(SLAVE) Multiphase Clocking Applications Information Quick-Start Multiphase Setup Quick Setup: Design the Master Phase Quick Setup: Design the Slave Phase(s) Quick Setup: Evaluation Choosing the Total Number of Phases Operating Frequency Selection CIN and COUT Selection CIN and COUT Selection: VIN Capacitance CIN and COUT Selection: VOUT Capacitance VINHIMON, VOUTLOMON and RVSOFF Configuring the IIN(SLAVE) Current Limits Regulating IOUT(SLAVE) IOUT(SLAVE): Circuit Description IOUT(SLAVE): Configuration Loop Compensation Voltage Lockouts Circuit Board Layout Checklist Design Example Typical Applications Package Description Typical Application Related Parts
