Datasheet LT8708 (Analog Devices) - 4

LT8708
ELECTRICAL CHARACTERISTICS The
l
denotes the specifications which apply over the full operating 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 = 0V SWEN = 3.3V 3.9 6.5 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 Maximum 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 170 mV INTVCC Regulator Dropout Voltage VINCHIP – VINTVCC, IINTVCC = 20mA 220 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 Maximum 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, LT8708I) l 0.35 V (LT8708H) 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 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 Typical Performance Characteristics Pin Functions Block Diagram Operation Typographical Conventions Start-Up Start-Up: SHDN Pin Start-Up: SWEN Pin Start-Up: Soft-Start of Switching Regulator Control Overview Power Switch Control Switch Control: Buck Region (VIN >> VOUT) Switch Control: Buck-Boost (VIN ≅ VOUT) Switch Control: Boost Region (VIN << VOUT) Switch Control: Soft-Start Uni and Bidirectional Conduction Bidirectional Conduction: CCM Unidirectional Conduction: DCM Unidirectional Conduction: HCM Unidirectional Conduction: Burst Mode Error Amplifiers VOUT Regulation and Sensing VOUT: Regulation VOUT: Above Regulation VOUT: Below Regulation and Undervoltage VIN Regulation and Sensing VIN: Regulation VIN: Above Regulation and Overvoltage VIN: Below Regulation Current Monitoring and Limiting Monitoring and Limiting: IMON Pins Monitoring: ICP and ICN Pins INTVCC/EXTVCC/GATEVCC/LDO33 Power CLKOUT and Temperature Sensing Applications Information Verify the Power Flow Conditions Operating Frequency Selection Internal Oscillator SYNC Pin and Clock Synchronization CLKOUT Pin and Clock Synchronization Inductor Current Sensing and Slope Compensation RSENSE Selection and Maximum Current RSENSE Selection: Max RSENSE in the Boost Region RSENSE Selection: Max RSENSE in the Buck Region RSENSE Selection: Final RSENSE Value RSENSE Filtering Inductor (L) Selection L Selection: Load Current in Buck and Boost Regions L Selection: Subharmonic Oscillations L Selection: Maximum Current Rating Power MOSFET Selection CIN and COUT Selection Schottky Diode (D1, D2, D3, D4) Selection Topside MOSFET Driver Supply (CB1, DB1, CB2, DB2) Top Driver: Boost Cap Charge Control Block Top Driver: Boost Diodes DB1 and DB2 VINHIMON, VOUTLOMON and RVSOFF IIN and IOUT Current Monitoring and Limiting Loop Compensation INTVCC Regulators and EXTVCC Connection LDO33 Regulator Voltage Lockouts Junction Temperature Measurement Thermal Shutdown Efficiency Considerations Circuit Board Layout Checklist Hot Plugging Considerations Design Example Typical Applications Package Description Typical Application Related Parts