Datasheet LT8708-1 (Analog Devices) - 4

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 Voltage Supplies and Regulators
VINCHIP Operating Voltage Range EXTVCC = 0V l 5.5 80 V EXTVCC = 7.5V l 2.8 80 V VINCHIP Quiescent Current Not Switching, VEXTVCC = 0 SWEN = 3.3V 4.7 7.5 mA SWEN = 0V 2.45 4.5 mA VINCHIP Quiescent Current in Shutdown VSHDN = 0V 0 1 µA EXTVCC Switchover Voltage IINTVCC = –20mA, VEXTVCC Rising l 6.15 6.4 6.6 V EXTVCC Switchover Hysteresis 0.2 V INTVCC Current Limit Max Current Draw from INTVCC and LDO33 Pins Combined. Regulated from VINCHIP or EXTVCC (12V) INTVCC = 5.25V l 90 127 165 mA INTVCC = 4.4V l 28 42 55 mA INTVCC Voltage Regulated from VINCHIP, IINTVCC = 20mA l 6.1 6.3 6.5 V Regulated from EXTVCC (12V), IINTVCC = 20mA l 6.1 6.3 6.5 V INTVCC Load Regulation IINTVCC = 0mA to 50mA –0.5 –1.5 % INTVCC, GATEVCC Undervoltage Lockout INTVCC Falling, GATEVCC Connected to INTVCC l 4.45 4.65 4.85 V INTVCC, GATEVCC Undervoltage Lockout Hysteresis GATEVCC Connected to INTVCC 160 mV INTVCC Regulator Dropout Voltage VINCHIP – VINTVCC, IINTVCC = 20mA 245 mV LDO33 Pin Voltage 5mA from LDO33 Pin l 3.23 3.295 3.35 V LDO33 Pin Load Regulation ILDO33 = 0.1mA to 5mA –0.25 –1 % LDO33 Pin Current Limit SYNC = 3V l 12 17.25 22 mA LDO33 Pin Undervoltage Lockout LDO33 Falling 2.96 3.04 3.12 V LDO33 Pin Undervoltage Lockout Hysteresis 35 mV
Switching Regulator Control
Maximum Current Sense Threshold (VCSP – VCSN) Boost Mode, Minimum M3 Switch Duty Cycle l 76 93 110 mV Maximum Current Sense Threshold (VCSN – VCSP) Buck Mode, Minimum M2 Switch Duty Cycle l 68 82 97 mV Maximum Current Sense Threshold (VCSN – VCSP) Boost Mode, Minimum M3 Switch Duty Cycle l 79 93 108 mV Maximum Current Sense Threshold (VCSP – VCSN) Buck Mode, Minimum M2 Switch Duty Cycle l 72 84 96 mV Gain from VC to Max Current Sense Voltage Boost Mode 135 mV/V (VCSP – VCSN) (A5 in the Block Diagram) Buck Mode –135 mV/V SHDN Input Voltage High SHDN Rising to Enable the Device l 1.175 1.221 1.275 V SHDN Input Voltage High Hysteresis 40 mV SHDN Input Voltage Low Device Disabled, Low Quiescent Current (LT8708E-1, LT8708I-1) l 0.35 V (LT8708H-1) l 0.3 V SHDN Pin Bias Current VSHDN = 3V 0 1 µA VSHDN = 12V 14 22 µA SWEN Rising Threshold Voltage l 1.156 1.208 1.256 V SWEN Threshold Voltage Hysteresis 22 mV SWEN Output Voltage Low ISWEN = 200µA SHDN = 0V or VINCHIP = 0V l 0.9 1.1 V SHDN = 3V l 0.2 0.5 V SWEN Internal Pull-Down Release Voltage SHDN = 3V l 0.75 0.8 V Rev 0 4 For more information www.analog.com 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