150V synchronous step-down DC/DC controller
Analog Devices, Inc. has announced the LTC7801, a high voltage non-isolated synchronous step-down switching regulator controller in compact 24-lead packages that drives an all N-channel MOSFET power stage. Its 4V to 140V (150V 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 reportedly continues to operate at up to 100% duty cycle during input voltage dips down to 4V, making it well suited for transportation, industrial control, robotic, and datacom applications.
The output voltage can be set from 0.8V to 60V at output currents up to 20A with efficiencies as high as 96%. The device draws 40µA in sleep mode with the output voltage in regulation. An internal charge pump allows for 100% duty cycle and operation in dropout. The LTC7801’s 1Ω N-channel MOSFET gate drivers can be adjusted from 5V to 10V 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 50kHz and 900kHz and is synchronizable to an external clock from 75kHz to 850kHz. The user can select from forced continuous operation, pulse-skipping, or low ripple Burst Mode operation during light loads. Its current mode architecture provides loop compensation, transient response, and 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 80ns 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 4mm x 5mm QFN-24 and TSSOP-24 thermally enhanced packages. Two operating junction temperature grades are available: extended and industrial versions from –40 to 125°C and a high temp automotive version from –40°C to 150°C. For more information, visit www.linear.com/product/LTC7801.