Analog Devices builds on surge stopper portfolio
Equipped over-voltage and over-current protection for high availability systems, the latest Power by Linear surge stopper drives an n-channel power MOSFET stage.
During normal operation, the LTC7862 passes the input voltage through to the output with minimal conduction loss. When an input over-voltage condition occurs, the LTC7862 starts switching as a high efficiency DC/DC regulator, protecting critical downstream components by limiting the output voltage and current.
The LTC7862 builds on Analog Devices’ existing linear surge stoppers, such as the LTC4363, by offering high efficiency switching protection to extend output current capability and reduce power loss during transients and faults. Supply voltages surge when the load current changes abruptly in long inductive power buses. In automotive applications, energy stored in the alternator’s inductance causes an elevated and extended voltage surge during a load dump. The power handling capability of a surge stopper is limited by the power lost in the protection circuit. In a linear surge stopper, the power capability is determined by the size of the pass MOSFET, while in a switching surge stopper the power capability is determined by conversion efficiency. Due to its lower power loss, a switching surge stopper can operate through longer input voltage surges at higher output current than a linear surge stopper.
The LTC7862 has an input voltage operating range of 4.0 to 140V, 150V absolute maximum. An external fault timer capacitor configures the limited time spent in over-voltage mode and keeps the switching surge stopper below a safe peak operating temperature when power loss is at its highest levels. The fault timer saves system cost and size by allowing component selection to be optimised for normal mode rather than over-voltage transient and fault conditions.
In Mil-Std-1275 applications the LTC7862 protects devices operating from a 28V vehicle power bus, where this bus voltage can reach as high as 100V and last up to 500 milliseconds. The LTC7862 also fits into industrial, avionics, and automotive power, including ISO 7637.
The LTC7862 is available in 20-lead 4.0 x 5.0mm TSSOP and QFN packages. Three temperature grades are available, operating from -40 to +125 degree C for the extended and industrial grades and -40 to +150 degree C for the high temperature automotive grade device.
