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20 \ VISHAY An Automotive Grade Above available with different transfer gain (K3) options. All that is required to implement an actual design is to supply an input signal in the intended IP1 current range and use the voltage from the feedback PIN (P1) as feedback to the IRLED driver. The most common approach is to use an operational amplifier to directly drive the IRLED. Figures 3 and 4 provide examples of how the VOA300 can be used to implement isolated current shunt measurements and high-voltage measurements. The current is measured using a Vishay WSBS8518-35 shunt (RS in Figure 3) that has integral sense pins for ease of mounting to the PCB. The resistance value selection is a compromise between the power losses and the output voltage signal-to-noise ratio. A s the electric/hybrid vehicle market continues to grow, original equipment manufacturers (OEMs) are increasing high-voltage bus levels to reduce the system currents and improve efficiency. As a result, the need to measure voltages and currents in the high-voltage battery pack used by the low- voltage control system becomes more difficult because they must be isolated from each other for safety reasons. Using a linear optocoupler is a cost-effective approach to achieving this purpose. An implementation of such a voltage and current- sensing module for a high-voltage battery management system (BMS) is shown in (Figure 1). The Vishay VOA300 linear optocoupler consists of an AlGaAs IRLED irradiating an isolated feedback (P1 in Figure 2) and an output PIN photodiode (P2 in Figure 2) in a bifurcated arrangement (Figure 2). The feedback photodiode captures a percentage of the LEDs flux and generates a control signal (IP1 in Figure 2) that can be used to control the LED drive current. This technique compensates for the LED's non-linear, time, and temperature characteristics. By using matched PIN photodiodes for the isolated feedback (P1) and output PIN photodiode (P2), the time and temperature stability of the input-output transfer gain (K3 in Figure 2) is insured. All these features result in the output signal (IP2 in Figure 2) tracking the feedback control signal (IP1 in Figure 2) under any operating condition, and the VOA300 is Voltage and Current Sensing for High- Voltage BMS VISHAY INTERTECHNOLOGY Figure 1: Voltage and current-sensing module for high-voltage BMS (Source: Vishay) Figure 2:Vishay VOA300 linear optocoupler (Source: Vishay)