FM5811DNCXXA is a new microwave radar sensor SOC chip launched by Silenet, which works in the 5.8GHz band and uses Doppler radar algorithm to recognize object motion. This SOC chip has the significant advantage of low power consumption and full integration, and compared with traditional radar sensor modules, it has the characteristics of cost-effective and good performance consistency. The built-in digital module of the chip, read and write through the standard I2C protocol, can allow the frequency to be flexibly adjusted within a fixed range, and the controllable performance of the gain effectively avoids all kinds of interference problems such as the same frequency interference and object miscontact, which is an intelligent induction scheme favored by lighting customers on the market.
    FM5811DNCXXA, as a new generation of RF SOC products from SPIL, adopts an ultra-low power architecture, which allows customers to realize more possibilities in the choice of auxiliary power. If the internal output signal of the chip is matched with the external MCU, that is, a complete microwave radar sensor is formed. This SOC radar sensor chip can meet a number of protocol standards, and has been successfully implemented in the field of intelligent lighting, smart home, intelligent control and other electronic products.

It works in the 5.8G ISM band
Microwave sensor based on Doppler effect
The sensing distance can be flexibly adjusted as required
Adopt mature CMOS technology to achieve fully integrated ultra-high cost performance
Chip built-in LDO, can effectively reduce the interference of external power supply
Supports standard I2C interface, can interwork with other master control or sensor
A variety of small size packages are available
QFN32 5x5 mm 2
QFN20 4x4 mm 2
QFN20 3x3 mm 2
Ultra-low power consumption, overall current about 25mA
IF signal output, with self-developed intelligent induction algorithm

Intelligent lighting
Smart home
Home appliance control
Intelligent sensing

    1. The PI network at the end of the RX antenna is used to match the input antenna, and the network parameters can be adjusted to optimize the RF performance when the linear impedance does not match;
    2. About the reference clock, the default is 25MHz crystal, such as MCU or other modules can provide a reference clock, which can save the crystal;
    3. The MCU configs the chip through I2C. If the I2C line is long, it is recommended to add 10k pull-up resistance on SDA and SCLK;
    4. The analog IF output of the chip has two channels, namely LPF_OUTP and LPF_OUTN, one of which can be selected for ADC sampling, and the other one can be used for IF signal pin PIN suspension processing;
    5. After sampling and simulating IF frequency, MCU needs to divide the specific power frequency signal filter by algorithm to reduce the influence of power frequency on induction performance;
    6. The radar signal is more sensitive to the ground, and the transmitting antenna and the receiving antenna are separated as far as possible in the PCB Layout;
    7. The typical power supply voltage of the chip is 3.3V. If the power supply voltage exceeds 3.5V, additional LDO is required.

    The structural framework of FM5811DNCXXA chip is shown in Figure 1. First, the phase-locked loop inside the chip generates a 5.8G RF and microwave signal, which is amplified by the transmitting antenna after the driver stage. When the RF and microwave signal meets a moving object, the transmitted signal and the reflected signal will produce Doppler radar effect, that is, there is a certain frequency difference between them. At this time, the reflected signal passes through the receiving antenna, is amplified by the low noise amplifier, and the transmitted signal is mixed in the mixer, and the mixer is processed to obtain an IF signal, and then the low-pass filter filters out the noise, and the IF signal is amplified at the same time. Finally, the high and low levels are output by digital processing through the single chip computer, and then judge whether there is a moving object around the sensor.

    FM5811DNCXXA supports a fast I2C mode with a maximum bit rate of 400kbit/S. The MCU can directly configure or read the status information of the chip through I2C, and its data transmission follows the format shown in Figure 5. After the initial condition (S), a 7-bit slave address 0X1A is sent, followed by the 8th bit R/W. '0' means send (write), '1' means request data (read), and data transmission is terminated by a stop bit (P) generated by the host.