Eliminating external surge protection devices

A high voltage non-isolated dual output synchronous step-down DC/DC controller that drives all N-channel MOSFET power stages has been announced by Analog Devices.

The Power by Linear LTC7810 is said to have an input voltage range of 4.5V to 140V (150V abs max) which is designed to operate from a high input voltage or from an input that has high voltage surges. The aim is to eliminate the need for external surge suppression devices.

According to Analog Devices, the LTC7810 operates at up to 100% duty cycle during input voltage dips down to 4.1V.

It continued that the output voltage can be set from 1V to 60V at output currents up to at least 20A per channel, with efficiencies up to 96%. This part is said to draw only 16µA in sleep mode from a 48V input, while regulating outputs at 12V and 3.3V.

The LTC7810’s 1Ω N-channel MOSFET gate drivers are designed to be programmed to 6V, 8V or 10V, which Analog Devices said will enable the use of logic-level or standard-threshold MOSFETs to maximise efficiency.

To prevent high on-chip power dissipation in high input voltage applications, the LTC7810 is said to be able to drive the gate of an optional external N-channel MOSFET, acting as a low dropout linear regulator, to supply IC power. The EXTVCC pin is designed to permit the LTC7810 to be powered from the output of the regulator or another available source, which should also reduce power dissipation, while improving efficiency.

The LTC7810 operates with a selectable fixed frequency between 50kHz and 750kHz and is designed to be synchronisable to an external clock from 75kHz to 720kHz.

The user should be able to select from forced continuous operation, pulse-skipping, or low ripple Burst Mode operation during light loads. Analog Devices has said it believes its current mode architecture should provide easy loop compensation, fast transient response and excellent line regulation.

Current sensing is accomplished by measuring the voltage drop across the output inductor, or by using an optional sense resistor. A low 90ns minimum on-time is also said to allow for high step-down ratios at high switching frequency and current foldback should limit MOSFET heat dissipation during overload conditions.