![]() The UIR sensor uses the same isolated daisy chain as the cell monitors sitting on the CSU, thus enabling the BJB and all of the CSUs to sit on the same isolated daisy-chain bus and communicate with the BMU. In intelligent BJBs, the UIR sensor communicates with the BMU as well as all other circuitry on the BJB, without the need for an MCU. On the other hand, an isolated daisy chain offers a simple, two-wire twisted-pair protocol that does not require any MCU or associated software, serving OEMs’ requirements for reduced complexity and lower bill-of-materials costs. The CAN approach requires that you place a safety MCU, CAN transceiver, and associated power circuits on the BJB. This new design architecture presents a new challenge: The intelligent BJB and BMU still need to communicate with each other through a Controller Area Network (CAN) bus or an isolated daisy chain, among other options. The BMU becomes a low-voltage–only board, reducing its complexity and cost. These intelligent BJBs significantly reduce the amount of cabling between the BMU and BJB while providing greater flexibility for locating the BMU and BJB in the battery pack. In response, manufacturers increasingly are moving electronics such as the UIR sensor (for pack voltage, current, and insulation resistance measurement), contactor drivers, and pyro fuse drivers to the BJB. The traditional BMS architecture requires many cables running between the BMU and BJB that consume precious real estate in the battery pack and add weight to the car. TI’s newest battery monitors and balancers, such as the BQ79616-Q1, support a broad spectrum of battery chemistries, including LiFePO 4, to improve cell-voltage–monitoring accuracy and enable precise SoC and SoH measurements. The CSU contains the electronics for cell voltage and temperature monitoring, and the BJB primarily functions as an electromechanical box where shunts, contactors, and pyro fuses are located. Additionally, most of the electronics needed for pack voltage and current monitoring, insulation resistance measurement, and contactor and pyro fuse drivers are on the BMU. ![]() Precise measurement of SoC and SoH is key to reducing cost and providing an accurate representation of battery life and driving range. The BMU contains the main BMS MCU, which is responsible for state-of-charge (SoC) and state-of-health (SoH) calculations of the battery pack. Intelligent BJBsĪ traditional BMS has three main subsystems: the battery management unit (BMU), BJB, and cell supervision unit (CSU). Intelligent battery junction boxes (BJBs) and domain-controlled BMS are the next evolutionary steps for EV BMS architecture, offering increased design flexibility, reduced software overhead, and higher battery pack performance. ![]() To get more miles out of a single charge, reduce charging times, and minimize the overall cost of EV battery packs, designers are adopting new battery chemistries and experimenting with new architectures. I need to "walk" on the resistance path -blue line- (and select A2 point as S11) OR on the imaginary part -red line- (and select A1 point as S11), which both do not make sense to me.EV high-voltage battery management system (BMS) technologies are evolving rapidly.Either the graph does not have information of S11 for a 50 Ω load (most probably?) so I need to match the impedance of 50 Ω that I have on the input to one of the drawn lines on the graph (green line) so that can I change my input impedance from 50 Ω to a known impedance and use this S parameter.Now, point A is not being crossed by any line, so my ideas to find the S11 there are: In the meanwhile I am posting my ideas since I am doing it as a homework project: My question is: How do I find the S11 parameter from this graph? ![]() S11 is on the input side, where I have a 50 Ω source, so the input (source) is on point A. For example, for the S11 I have the below figure from the datasheet. I am unsure as to how can I spot the S11 values from the Smith chart that the datasheet provides. Lets say that the input/output loads are 50 Ω. The design should be optimal for simultaneously matching impedance and maximum gain. I chose the BFP840ESDH6327XTSA1 as my RF transistor, to operate it at 10 mA, 12GHz. I am trying to understand S parameters on RF transistors.
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