Issue link: https://resources.mouser.com/i/1429079
22 \ VISHAY An Automotive Grade Above Intelligent Current Sense and Safety Switch for BMS, High Current Loads A s the current requirements continue to increase for both 12V and 48V vehicle systems, the need to replace conventional mechanical relays and contactors with new methods for life expectancy and safety is growing. The Intelligent Current Sense and Safety Switch (ICSS) (Figure 1), has been developed by Vishay specifically for battery management systems (BMS) and to control any high current vehicle loads. The design consists of a control board and a power stage and features pre-charge and current measurement functions. The ICSS is controlled via a CAN bus network for ease of vehicle integration so that the load can be switched on/off and the pre- charge parameters easily accessed. VISHAY INTERTECHNOLOGY To allow high currents to be switched safely and efficiently, without damaging the components because of thermal stress, the power stage (shown in Figure 2 with the control board removed) has been designed with bare die technology for optimal cooling. Because the power MOSFET die is not constrained by a plastic molded package, the heat can be efficiently transferred to the heatsink with very little loss. In this design, the Vishay SQC60002E_KGD (Known Good Die) were connected in a bi-directional arrangement (TR1/TR2 in Figure 3) to prevent backflow of current through the MOSFET body diode when the load is deactivated. A pre-charge function must be used to prevent component damage from a high in-rush current during the initial vehicle startup. In this design, a Vishay SQSA80ENW MOSFET (TR3 in Figure 3) and a Vishay DTO25 resistor (R2 in Figure 3) limit the in-rush current to a maximum of 5A at 48V. Power thick film resistors are ideal due to their superior power-handling. Before energizing the load, TR3 is switched on for a predefined time Figure 1: Intelligent Current Sense and Safety Switch (ICSS) (Source: Vishay)