Datasheet LT8708 (Analog Devices) - 5

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
SWEN Internal Pull-Down Release Voltage SHDN = 3V l 0.75 0.8 V MODE Pin Continuous Conduction Mode (CCM) l 0.4 V Threshold MODE Pin Hybrid DCM/CCM Mode (HCM) Range l 0.8 1.2 V MODE Pin Discontinuous Conduction Mode (DCM) l 1.6 2.0 V Range 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 ICN Rising Threshold for FDCM Operation MODE = 1V (HCM), DIR = 3.3V l 235 255 280 mV ICN 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
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 VINCHIP = 12V to 80V. Not Switching 0.002 0.005 %/V Reference Voltage 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 Out of Pin 0.03 μA VVINHIMON = 1.24V, Current Out of Pin l 0.8 1 1.2 μA
Current Regulation Loops (Refer to Block Diagram to Locate Amplifiers)
Regulation Voltages for IMON_INP and IMON_OP VC = 1.2V l 1.185 1.209 1.231 V Regulation Voltages for IMON_INN and IMON_ON VC =1.2V l 1.185 1.21 1.24 V 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 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