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I²C bus is a dual -line two -way serial bus developed by Philips. It is mainly used in short -range communication between the ICs in the board or the board of the board. The application is very wide.The main device of the I2C bus controls the serial clock line (SCL), and the data is transmitted in both directions on the serial data cable (SDA).The I2C bus can theoretically increase 112 communication nodes, but the number of nodes will increase the bus capacitor of the bus, thereby limiting the communication distance and communication speed.In practical applications, weighing between communication speed, bus length and number of nodes.I2C bus supports four transmission rates: standard mode (up to 100kbps), fast mode (up to 400kbps), rapid enhancement mode (maximum 1Mbps) and high -speed mode (maximum 3.4Mbps).Rongyao Semiconductor I2C isolate π220N31/π221N31 supports the above four communication rates.
As shown in Figure 1, in order to meet the requirements of security norms, avoid noise signal interference communication, and avoid damage to sensitive devices, I2C isolation products need to be used to isolate the device, such as the Rongyou I2C isolation product π220N31.
Figure 1 I2C isolation product applies in the system
There are four I2C isolation products products. The isolation resistance is divided into 3KV and 5KV. It corresponds to the SOP8 packaging 4mm climbing distance and the WSOP16 packaging 8mm.The serial clock SCL is divided into two -way and one -way.π220n31 and π220n61 are hot-selling models and meet the requirements of the AEC-Q100 specifications.The specific parameters of the four products are shown in Table 1.
Table 1 Rongyao I2C product parameter list
Rongyou I2C isolation device hot -selling products π220n31 and π220n61 pins definition and internal box diagram of the chip are shown in Figure 2, which can be compatible with SCL unidirectional products π221N31 and π221N61.The typical application circuit diagram of π220N31 is shown in Figure 3.
Figure 2 I2C isolation product pin definition and function box diagram
Figure 3 π220n31 typical application circuit diagram
Because the I2C interface is a leakage output, in order to achieve the reliable system of the system, a pull -up resistance is needed, as shown in Figure 3 R1 ~ R4.Pull resistance affects signal rising time and system current.Excessive pull -up resistance will cause the signal to rise too much, resulting in unable to communicate normally.If the pull -up resistance is too small, it will cause the system current to be too large and damage the sensitive device.Therefore, you need to choose the right pull -up resistance as needed.Because the upper pull resistance is related to the rise time, the different I2C communication rate specifies the maximum rise time, as shown in Table 2.
Table 2 The maximum rise time at different I2C communication rates
Based on the determined communication rate and know the maximum rise time, you can calculate the appropriate pull -up resistance.For example, the isolation system uses 3.3V power supply. Because the quarantine 1 side can withstand the irrigation current of 3.5mA, the minimum value of the pull -up resistance is 3.3V/3.5ma = 0.94k.At the same time, if you work in a fast mode, the rising time cannot exceed 300ns.Because TR (30%-70%) = 0.85rc, the load capacitance C assumes that the maximum load 40pf allowed by the isolation is that the maximum value of the pull resistor can be calculated.Therefore, the appropriate pull -up resistance is between 0.94k and 8.8K Euro, and you can choose 4.7k Euro.
The input and output level of the Rongyou I2C isolation device is the same as the I2C isolation product of other American manufacturers, not the standard TTL or CMOS level.as shown in Table 3.
Table 3 I2C isolate input output voltage
In order to solve the problem of low levels in the above system's interoperability, the low level L ' output from the side 1 of the isolator 1; the internal recognition of the chip needs to be recognized as a high level in order to not interfere with external communication.Therefore, the output of the isolator 1 is low -level L ' the threshold is required greater than the 1 side (the typical value of the threshold is 0.58V, so the input voltage is less than 0.45V).At the same time, the output of the isolator 1 on the side needs to be identified by the external device (such as MCU, ADC, etc.) to low levels (CMOS is less than 0.3VDD, and TTL is less than 0.8V).Therefore, the 1 -side output low voltage 0.58V & lt; l ' & lt; 0.8V, is set to 0.7V, which can not cause internal interoperability, but also can be recognized as a low level.& lt; p = & quot; & quot; & gt;
Rongyou I2C isolation product π220N31/π221N31 is designed based on the intelligent semiconductor patent (IDIVIDER technology).The technology has the advantages of low power consumption, short -term lattral, high rate, and good EMC performance.Rongyou I2C isolation products are widely used in the Ethernet power supply (POE) system, battery management system (BMS), and -48V distributed power system.This article explains the application of I2C isolation products in electric motorcycles BMS.
There are two main types of batteries in electric motorcycles, lead -acid batteries and lithium batteries.Lithium batteries have great advantages in terms of environmental protection, endurance, and battery life compared to lead -acid batteries.Therefore, the country vigorously promotes the application of lithium batteries.However, lithium batteries are easy to fail or even explode due to overwhelming, over pressure and overcurrent, so the management of lithium batteries in applications is particularly important.Most of the rated voltage of electric motorcycle batteries is 48V, 60V or 72V.
The BMS system with 20 string lithium batteries composed of 72V rated voltage is shown in Figure 5. The Rongyou I2C isolation product π220N31 is used for the isolation between the AFE chip and the MCU.Because in the BMS system, I hope to pass the energy as much as possible to the load, so the power consumption of the chip is relatively strict. The Rongyao Semiconductor I2C isolation product π220N31 is particularly suitable for applications in the BMS system with low power consumption performance.
Figure 5 BMS system with a rated voltage of 72V
The I2C bus is a two -line two -way serial bus, which is especially suitable for communication between ICs between the board or in -board.In order to meet the requirements of system security specifications, avoid noise signal interference communication, and avoid damage to sensitive devices, I2C isolation devices need to be added to the system for isolation.Rongyou I2C isolation product π220N31/π221N31 is designed based on the intelligent semiconductor patent (IDIVIDER technology).This technology has the advantages of low power consumption, short-term lattral, high rate, and good EMC performance. It has been widely used in the Ethernet power supply (POE) system, battery management system (BMS), and -48V distributed power system.
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