Datasheet LTC7804 (Analog Devices)

LTC7804 Low IQ Synchronous Boost Controller
FEATURES DESCRIPTION
n
Synchronous Operation for Highest Efficiency and
The LTC®7804 is a high performance synchronous boost
Reduced Heat Dissipation
DC/DC switching regulator control er that drives an al n
Wide VIN Range: 4.5V to 40V and Operates Down to
N-channel power MOSFET stage. Synchronous rectifica-
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 IQ: 14μA
architecture allows a phase-lockable switching frequency 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
RSENSE or Inductor DCR Current Sensing
supply as low as 1V after startup. 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 IQ: 1.2μA 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. The LTC7804 additionally features spread spectrum oper-
APPLICATIONS
ation which significantly reduces the peak radiated and n Automotive and Transportation conducted noise on both the input and output supplies, n Industrial making it easier to comply with electromagnetic interfer- n Military/Avionics ence (EMI) standards. n Telecommunications All registered trademarks and trademarks are the property of their respective owners. Protected by U.S. patents, including 5481178, 5705919,5929620, 6144194, 6177787, 6580258.
TYPICAL APPLICATION Efficiency and Power Loss
2µH 2mΩ
vs Output Current
VIN VOUT 4.5V TO 38V 24V 100 10k 6A 10µF VBIAS RUN SENSE+ 90 10µF 150µF BURST EFFICIENCY SENSE– ×2 80 1k BG POWER LOSS (mW) 70 ITH V LTC7804 OUT FOLLOWS VIN FOR VIN > 24V 8.06k 60 100 SS TG BURST LOSS 220pF SW 50 0.1µF 0.1µF 22nF BOOST 40 10 EFFICIENCY (%) 30 EXTV V CC IN = 12V INTVCC 20 1 FREQ VOUT = 24V 4.7µF MODE Burst Mode OPERATION 10 604k PLLIN/SPREAD FIGURE 9 CIRCUIT 0 0.1 GND VFB 0.00001 0.0001 0.001 0.01 0.1 1 10 31.6k 7804 TA01a OUTPUT CURRENT (A) 7804 TA01b Rev. 0 Document Feedback For more information www.analog.com 1 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