150V synchronous step-down DC/DC controller with surge protection
The LTC7801 continues to operate at up to 100% duty cycle during input voltage dips down to 4V, suiting it for transportation, industrial control, robotic and datacom applications. Its 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 40 µA in sleep mode with the output voltage in regulation, for always-on systems. An internal charge pump allows for 100% duty cycle and operation in dropout, a useful feature when powered from a battery during discharge. 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 50 kHz and 900 kHz and is synchronizable to an external clock from 75 kHz 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 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. 80 nsec 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 occupies 4 x 5 mm 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. Pricing starts at $4.20 (1000).
Analog Devices/Linear Technology; www.linear.com/product/LTC7801
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