LTC7804 ELECTRICAL CHARACTERISTICSThe l denotes the specifications which apply over the specified operatingjunction temperature range, otherwise specifications are for TA = 25°C, VBIAS = 12V, RUN = 12V, EXTVCC = 0V, unless otherwise noted.(Note 2)SYMBOLPARAMETERCONDITIONSMINTYPMAXUNITSInput Supply VBIAS Bias Input Supply Operating Range 4.5 40 V VIN Boost Converter Input Supply Operating Range VBIAS ≥ 4.5V 1 40 V VOUT Output Voltage Operating Range 40 V Controller Operation VFB Regulated Feedback Voltage (Note 3) VBIAS = 4.5V to 40V, ITH Voltage = 0.6V to 1.2V l 1.188 1.2 1.212 V Feedback Current (Note 3) ±5 ±50 nA Feedback Overvoltage Protection Threshold Measured at VFB Relative to Regulated VFB 7 10 13 % gm Transconductance Amplifier gm (Note 3) ITH = 1.2V, Sink/Source = 5μA 2 mmho VSENSE(MAX) Maximum Current Sense Threshold VFB = 1.1V, VSENSE+ = 12V l 45 50 55 mV ISENSE+ ISENSE+ Pin Current VSENSE+ < 2.9V 2 μA 3.2 ≤ VSENSE+ ≤ INTVCC −0.5V 30 μA VSENSE+ > INTVCC + 0.5V 650 μA ISENSE− SENSE− Pin Current VSENSE− = 12V ±1 μA Soft-Start Charge Current VSS = 0V 10 12.5 15 µA RUN Pin ON Threshold VRUN Rising l 1.15 1.2 1.25 V RUN Pin Hysteresis 100 mV DC Supply Current (Note 4) IQ VBIAS Shutdown Current RUN = 0V 1.2 μA VBIAS Sleep Mode Current VSENSE+ < 2.9V, EXTVCC = 0V 14 28 μA VSENSE+ ≥ 3.2V VBIAS Current, EXTVCC = 0V 5 μA VBIAS Current, EXTVCC ≥ 4.8V 1 μA EXTVCC Current, EXTVCC ≥ 4.8V 4 μA SENSE+ Current 9 μA Pulse-Skipping or Forced Continuous Mode VFB = 1.25V 2 mA VBIAS or EXTVCC Current Gate Drivers TG or BG On-Resistance Pull-Up 3.0 Ω Pull-Down 1.5 Ω TG or BG Transition Time (Note 5) Rise Time CLOAD = 3300pF 25 ns Fall Time CLOAD = 3300pF 15 ns TG Off to BG On Delay CLOAD = 3300pF Each Driver Bottom Switch-On Delay Time 15 ns BG Off to TG On Delay CLOAD = 3300pF Each Driver Synchronous Switch-On Delay Time 15 ns tON(MIN) BG Minimum On-Time (Note 6) 80 ns Maximum Duty Factor for TG Overvoltage 100 % Maximum Duty Factor for BG VFREQ = 0V 93 % Rev. 0 For more information www.analog.com 5 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Main Control Loop INTVCC/EXTVCC Power Boost Supply and Dropout (BOOST and SW Pins) Shutdown and Start-Up (RUN, SS Pins) Light Load Current Operation: Burst Mode Operation, Pulse-Skipping or Forced Continuous Mode (MODE Pin) Frequency Selection, Spread Spectrum and Phase-Locked-Loop (FREQ and PLLIN/SPREAD Pins) Operation When VIN > VOUT Operation at Low Input Voltage BOOST Supply Refresh and Internal Charge Pump Applications Information SENSE+ and SENSE– Pins Low Value Resistor Current Sensing Inductor DCR Sensing Inductor Value Calculation Inductor Core Selection Power MOSFET Selection CIN and COUT Selection Setting Output Voltage RUN Pin Soft-Start (SS Pin) INTVCC Regulators Topside MOSFET Driver Supply (CB, DB) Phase-Locked Loop and Frequency Synchronization Setting the Operating Frequency Selecting the Light-Load Operating Mode Minimum On-Time Considerations Fault Conditions: Overtemperature Protection Efficiency Considerations Checking Transient Response Design Example PC Board Layout Checklist PC Board Layout Debugging Package Description Typical Application Related Parts
