LTC3878 Fast, Wide Operating Range No RSENSE Step-Down DC/DC Controller FeaTures DescripTion n Wide VIN Range: 4V to 38V The LTC®3878 is a synchronous step-down switching n ±1% 0.8V Voltage Reference DC/DC controller optimized for high switching frequency n Extremely Fast Transient Response and fast transient response. The constant on-time valley n tON(MIN): 43ns current mode architecture allows for a wide input range, n No RSENSE™ Valley Current Mode Control including very low duty factor operation. No external sense n Stable with Low ESR Ceramic COUT resistor or slope compensation is required. The LTC3878 n Supports Smooth Start-Up Into Pre-Biased Output is pin compatible with the LTC1778 in applications that do n Optimized for High Step-Down Ratios not use EXTVCC while offering better efficiency. Consult n Pin
Compatible with the
LTC1778 (No EXTVCC Pin) with the factory to verify compatibility. n Power Good Output Voltage Monitor Operating frequency is set by an external resistor and n Dual N-Channel MOSFET Synchronous Drive compensated for variations in VIN to offer excellent line n Adjustable Switching Frequency stability. Discontinuous mode operation provides high n Programmable Current Limit with Foldback efficiency during light load conditions. A forced continu- n Output Overvoltage Protection ous control pin allows the user to reduce noise and RF n Small 16-Pin Narrow SSOP Package interference. Safety features include output overvoltage applicaTions protection and programmable current limit with foldback. Soft-start capability for supply sequencing is accomplished n Distributed Power Systems through an external timing capacitor. The current limit is n Embedded Computing user programmable. n Communications Infrastructure The LTC3878 allows operation from 4V to 38V at the input L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear and from 0.8V to 90% V Technology Corporation. No R IN at the output. The LTC3878 is SENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. available in a small 16-pin narrow SSOP package. Protected by U.S. Patents, including 5481178, 6100678, 6580258, 5847554, 6304066. Typical applicaTion High Efficiency Step-Down ConverterEfficiency vs Load Current 100 0.1µF 432k DISCONTINUOUS I 90 ON MODE RUN/SS V V IN IN 80 4.5V TO 28V 220pF TG RJK0305 70 12.1k LTC3878 10µF I CONTINUOUS TH SW 0.56µH VOUT 60 SGND BOOST 1.2V MODE 50 FCB 15A 0.22µF 40 INTVCC 330µF EFFICIENCY (%) BG RJK0330 s2 30 4.7µF 20 VIN = 12V PGOOD PGND VOUT = 1.2V V 10 SW FREQ = 400kHz RNG 5.11k FIGURE 7 CIRCUIT V 0 FB 0.01 0.1 1 10 100 10k LOAD CURRENT (A) 3878 TA01a 3878 G07 3878fa Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration order information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts
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