The legend is a typical BMS control panel based on NXP core automotive device.
As the main part of board level ESD control, it is the 3 way CAN communication and the external communication interface of RS485 and RS232,
This program features high reliability ESD protection, support for hot plug and random battery connection protection.
The following is the three tage protection scheme for interface design.
1, CAN interface
In the comprehensive comparison of various field bus, CAN bus communication system based on construction has many excellent characteristics: data using differential signal transmission bus voltage; transmission medium can be twisted pair, coaxial cable and optical fiber; can be multi master mode, flexible communication mode; can point to point and point to multipoint and global broadcast transmitting and receiving data; node information on the network can be divided into different priority, meet the real-time requirements of different.

In the device, CAN protocol as the main channel of communication control unit interaction, the communication rate as high as 1Mbps, wide input common mode range of the differential signal and the neural network technology like the human body, so the protection of CAN becomes more and more important.
For car level protection, the ESD‘s antistatic capability needs to meet tests that meet the IEC61000-4-2 standards and the air is up to 30KV.
The protection requirements based on CAN, SMC24 electrostatic protection device from development, using the SOT-23 package, working voltage 24V, meet 12V automotive systems products 24V to maintain a 1 minute test at the same time can also protect the 2 CAN signals, because of its own characteristics of low junction capacitance, can not satisfy the CAN data packet communication.

2, RS485 interface
The characteristics of the RS485 interface is asymmetric transceiver level, 7V and 12V, so it is necessary to protect the chip designed asymmetric, and the SM712 SOT-23 package, designed to protect with asymmetric voltage (-7V to 12V) and the design of the RS-485 application, from the electrostatic discharge (ESD), electrical fast transient (EFT the harm caused by lightning surge current) and bring. It can absorb the higher repeatability ESD discharge 30KV the highest level IEC 61000-4-2 international standard, there is no need to worry about the performance decline, and at a very low clamping voltage safely under 19A 8/20 S wave dissipation surge current (IEC61000-4-5).

3, RS232 interface
The RS232 interface is the internal configuration interface, or the short distance and low communication port, but this interface is often inserted, needs to use the power of more than 300W products of electrostatic and surge protection, so need to use SOD-323 package SD12C or SD15C (according to the voltage fluctuation of different chip customers) to protect the transceiver 2 signals.

4, ESD device layout proposal
A) put the device as close to the input or connector as possible.
(b) minimize the path length between the device and the protected line.
(c) keep the parallel signal path to a minimum.
(d) avoid operating a protected conductor in parallel with an unprotected conductor.
E) minimize all printed circuit board (PCB) conductive loops, including power supplies and ground loops.
(f) minimize the length of the transient return path to the ground.
G) avoid using shared transient return paths to common ground points.
H) use ground planes as much as possible, multilayer printed circuit boards, using ground vias.
Is it possible to appreciate the ESD protection program for this battery management system, BMS? If there is doubt about the ESD device or related problems can be directly linked to the official website of the online electronic us to staff oh! I wish you a happy life!