Analog Devices, Inc., which recently acquired Linear Technology Corporation, announces the LTC7801, a high voltage nonisolated synchronous step-down switching regulator controller in compact 24-lead packages that drives an all N-channel MOSFET power stage. Its 4 to 140 V (150 V abs max) input voltage range is designed to operate from a high input voltage source or from an input that has high voltage surges, eliminating the need for external surge suppression devices. The LTC7801 continues to operate at up to 100 percent duty cycle during input voltage dips down to 4 V, making it well suited for transportation, industrial control, robotic and datacom applications.
The output voltage can be set from 0.8 to 60 V at output currents up to 20 A with efficiencies as high as 96 percent. The device draws only 40 µA in sleep mode with the output voltage in regulation, ideal for always-on systems. An internal charge pump allows for 100 percent duty cycle and operation in dropout, a useful feature when powered from a battery during discharge. The LTC7801’s powerful 1Ω N-channel MOSFET gate drivers can be adjusted from 5 to 10 V to enable the use of logic- or standard-level MOSFETs to maximize efficiency. To prevent high on-chip power dissipation in high input voltage applications, the LTC7801 includes an NDRV pin, which drives the gate of an optional external N-channel MOSFET acting as a low dropout linear regulator to supply IC power. The EXTVCC pin permits the LTC7801 to be powered from the output of the switching regulator or other available source, reducing power dissipation and improving efficiency.
The LTC7801 operates with a selectable fixed frequency between 50 and 900 kHz and is synchronizable to an external clock from 75 to 850 kHz. The user can select from forced continuous operation, pulse-skipping or low ripple Burst Mode® operation during light loads. Its current mode architecture provides easy loop compensation, fast transient response and excellent line regulation. Current sensing is accomplished by sensing the voltage drop across the output inductor (DCR) for highest efficiency or by using an optional sense resistor. A low 80 ns minimum on-time allows for high step-down ratios at high switching frequency. Current foldback limits MOSFET heat dissipation during overload conditions. Additional features include an integrated bootstrap diode, a power good output signal, adjustable input overvoltage lockout and soft-start.
The LTC7801 is available in 4 mm x 5 mm QFN-24 and TSSOP-24 thermally enhanced packages. Two operating junction temperature grades are available: extended and industrial versions from –40°C to 125°C and a high temp automotive version from –40°C to 150°C. The 1000-piece price starts at $4.20 each. For more information, visit www.linear.com/product/LTC7801.