POWER LOSS (mW) LTC7804 Low I Synchronous Boost Controller Q with Spread Spectrum FEATURES DESCRIPTION n Synchronous Operation for Highest Efficiency and The LTC7804 is a high performance synchronous boost Reduced Heat Dissipation DC/DC switching regulator controller that drives an all n Wide V Range: 4.5V to 40V and Operates Down to N-channel power MOSFET stage. Synchronous rectifica- IN 1V After Start-Up tion increases efficiency, reduces power losses and eases n Output Voltage Up to 40V thermal requirements. A constant frequency current mode n Low Operating I : 14A architecture allows a phase-lockable switching frequency Q n Spread Spectrum Operation of up to 3MHz. The LTC7804 operates from a wide 4.5V n Pass-Thru/100% Duty Cycle Capability for to 40V input supply range. When biased from the boost Synchronous MOSFET converter output , the LTC7804 can operate from an input n R or Inductor DCR Current Sensing supply as low as 1V after startup. SENSE n Programmable Fixed Frequency (100kHz to 3MHz) The very low no-load quiescent current extends operating n Phase-Lockable Frequency (100kHz to 3MHz) runtime in battery powered systems. OPTI-LOOP com- n Selectable Continuous, Pulse-Skipping, or Low pensation allows the transient response to be optimized Ripple Burst Mode Operation at Light Loads over a wide range of output capacitance and ESR values. n Low Shutdown I : 1.2A Q The MODE pin selects among Burst Mode operation, n Thermally Enhanced 16-Pin 3mm 3mm QFN and pulse-skipping mode, or continuous inductor current MSOP Packages mode at light loads. n AEC-Q100 Qualification in Progress The LTC7804 additionally features spread spectrum oper- ation which significantly reduces the peak radiated and APPLICATIONS conducted noise on both the input and output supplies, n Automotive and Transportation making it easier to comply with electromagnetic interfer- n Industrial ence (EMI) standards. n Military/Avionics All registered trademarks and trademarks are the property of their respective owners. Protected n Telecommunications by U.S. patents, including 5481178, 5705919,5929620, 6144194, 6177787, 6580258. TYPICAL APPLICATION High Efficiency Wide Input Range 375kHz 24V/6A Boost Converter Efficiency and Power Loss 2H 2m vs Output Current V V IN OUT 4.5V TO 38V 24V 100 10k 6A VBIAS 10F + RUN SENSE 90 10F 150F BURST EFFICIENCY SENSE 2 80 1k BG 70 V FOLLOWS V OUT IN ITH LTC7804 FOR V > 24V IN 60 100 TG 8.06k SS BURST LOSS 220pF SW 50 0.1F 0.1F 22nF BOOST 40 10 30 V = 12V EXTV CC IN INTV CC 20 1 V = 24V FREQ OUT 4.7F Burst Mode OPERATION MODE 10 604k FIGURE 9 CIRCUIT PLLIN/SPREAD 0 0.1 GND V FB 0.00001 0.0001 0.001 0.01 0.1 1 10 31.6k 7804 TA01a OUTPUT CURRENT (A) 7804 TA01b Rev. A 1 Document Feedback For more information www.analog.com EFFICIENCY (%)LTC7804 TABLE OF CONTENTS Applications Information ................................ 15 Features ..................................................... 1 + SENSE and SENSE Pins ....................................... 15 Applications ................................................ 1 Low Value Resistor Current Sensing ....................... 16 Typical Application ........................................ 1 Inductor DCR Sensing ............................................ 16 Description.................................................. 1 Inductor Value Calculation ...................................... 17 Absolute Maximum Ratings .............................. 3 Inductor Core Selection .......................................... 17 Pin Configuration .......................................... 3 Power MOSFET Selection ....................................... 18 Order Information .......................................... 4 C and C Selection ........................................... 18 Electrical Characteristics ................................. 5 IN OUT Setting Output Voltage............................................ 19 Typical Performance Characteristics ................... 7 RUN Pin .................................................................. 19 Pin Functions .............................................. 10 Soft-Start (SS Pin) ..................................................20 Block Diagram ............................................. 11 INTV Regulators ..................................................20 Operation................................................... 12 CC Topside MOSFET Driver Supply (C , D ) ................21 Main Control Loop .................................................. 12 B B Phase-Locked Loop and Frequency INTV /EXTV Power ........................................... 12 CC CC Synchronization .....................................................21 Shutdown and Start-Up (RUN, SS Pins) ................ 12 Setting the Operating Frequency.............................22 Light Load Current Operation: Burst Mode Operation, Selecting the Light-Load Operating Mode ...............23 Pulse-Skipping or Forced Continuous Mode Minimum On-Time Considerations.......................... 24 (MODE Pin) ............................................................. 12 Fault Conditions: Overtemperature Protection ........ 24 Frequency Selection, Spread Spectrum and Phase- Efficiency Considerations ....................................... 24 Locked-Loop (FREQ and PLLIN/SPREAD Pins) ...... 13 Checking Transient Response .................................25 Operation When V > V IN OUT .............................................. 14 Design Example ......................................................25 Operation at Low Input Voltage .............................. 14 PC Board Layout Checklist .....................................26 BOOST Supply Refresh and Internal Charge Pump . 14 PC Board Layout Debugging ...................................27 Typical Applications ...................................... 28 Package Description ..................................... 32 Revision History .......................................... 33 Typical Application ....................................... 34 Related Parts .............................................. 34 Rev. A 2 For more information www.analog.com