【Guide】With the enrichment of car functions, USB2.0/3.0, power input port, buttons, SD card slot, etc. are widely used. ESD, inrush current, load dump, and short-to-load etc. become the focus of hardware designers because of the following points. For example, in the dry season, static electricity destroys ICs or any other ESD sensitive devices in the equipment through these interfaces; the inrush current generated by the switch of the equipment power supply, the start and stop of the car, and the misoperation of personnel poses a threat to the circuit and causes some components to fail. happen etc. In addition, for BMS systems, circuit overcurrent, lithium battery overcurrent and circuit EFT/spikes may damage Electronic devices in the circuit.

Generally, automotive electronic equipment includes two systems: automotive electronic control devices (subsystems including transmission control, safety control, body control, and drive system control); Auto Accessories (can be used independently in the automotive environment and have no direct relationship with the car itself) related electronic devices), such as GPS, OBD, Carcorder.

GPS/OBD/Carcorder Solution

List of Design-Related Parts

Power Board

OCP: PPTC device (2920L260/24DR-A or 2016L050MR)

OVP: TVS device (TPSMD18A or TPSMB18A)

※ PPTC can be replaced by NANO series fuse

● CAN BUS

For CAN bus, ESD and surge are the main problem points and cannot be ignored.

Recommended model: SM24CANA-02HTG or SMF18A

※ Considering the PCB space constraints, 2 pcs SMF18A is more advantageous.

● OBD signal port

For the OBD signal port, OCP (PPTC) and OVP (TVS) protection devices are recommended as follows:

【PPTC】0603L004YR, 1210L005WR, 1812L110/33DR-A

【TVS】SMF18A, SM15-02HTG

※ 8~13pcs of PPTC and TVS diodes will be used here. In addition, if the PCB space is limited, 1pcs of SM15 can replace 2pcs of SMF.

BMS solution

List of Design-Related Parts

● BMS protection circuit

For the active current sharing topology of BMS, the overcurrent and overvoltage protection reference design recommendations are as follows:

Overcurrent protection:

① DC Bus: L50/70QS series

② Current sharing protection board: 440/467 series

③ Battery cell: 0603L050PR

Overvoltage protection:

① MOS: SD05-01FTG

② CAN connector: SM24CANA-02HTG or SM24CANB-02HTG (TVS array）

Remarks: For the CAN interface, if you need high-demand surge protection, you can choose the SMBJ series of TVS.

In summary, for both Auto Accessories and BMS applications, over-current protection and over-voltage protection are required. PPTC is the most common overcurrent protection device, while TVS is the most common overvoltage protection device. But different terminals will have different requirements, so the selection is very important in practical applications.