ADI creates "gold finger" with unique ingenuity, and the traditional switch is revolutionized

The picture below shows the gold cantilever arm, which ADI engineers privately call the "Gold Fingers" . It is a small structure, only 6 microns thick, and has 5 fingers (contacts) as its nickname implies. ADI has invested a lot of money in the research and development of gold plating technology and uses a dedicated MEMS production line to create these highly consistent products.

The "Golden Finger" uses electrostatic action to apply a high-voltage DC voltage under the cantilever beam to control the switch to turn on. When turned on, the electrostatic attraction pulls the cantilever down, and all five contacts are lowered. The on-resistance of each contact is 5 ohms. After the combination, the overall on-resistance will be much smaller, allowing more power to pass. After testing, the transmission power of the " Golden Finger " can reach 36dBm.

The cantilever beam is made of gold, but the gold-to-gold contact design is not conducive to improving the operating life, so the contact material is changed to carbide metal, and its service life - that is, the number of switching times - is greatly improved.

The actual moving distance of the " gold finger " when it is turned on is only 0.3 microns. The tiny moving distance and ADI's patented sealed shell technology help improve reliability. Reliability is the key to mechanical design! Eric Carty , a senior application engineer at ADI who participated in the design of the " gold finger " , said:

MEMS switches require high voltage to electrostatically actuate the switch. To make the device as easy to use as possible and further guarantee performance, Analog Devices has designed a companion driver integrated circuit (IC) to generate the high DC voltage, which is co-packaged with the MEMS switch in a QFN form factor.

Eric pointed out: "In the past, some people tried to make MEMS switches, but they never succeeded in integrating the driver inside the same package. This is easy for ADI. ADI has a lot of experience in DC/DC converter and charge pump technology. We integrated the driver inside to enhance the ease of use and improve the user experience. This is the second breakthrough."

Four sets of " golden fingers "

Packaging is the third breakthrough. ADI RF MEMS has achieved the same size as a solid-state switch, with a height of only 1mm and a packaging area of ​​5mmX4mm, which is 20 times smaller than existing relays. Because of its very small size, the actual parasitic effect of the device is also very small, which has an inherent advantage when a large bandwidth is required. After testing, its bandwidth can be as high as 100GHz. "It is a low-capacitance, high-bandwidth switch by nature! What really limits the bandwidth is the package, not the small MEMS switch device inside the package. The small size can bring more imagination to circuit design." Eric concluded.

The " gold finger " and the driver IC are in the same plastic package, with a package area of ​​only 5mmX4mm

The fourth breakthrough lies in its excellent performance, including high bandwidth, low insertion loss, low power consumption and extremely high linearity. "The bandwidth can be up to 100GHz, the switch on-resistance is less than 2 ohms, the typical power consumption does not exceed 20mW, and the IP3 is close to 69dBm." Eric knows all the products he has created.

MEMS switches can be well used in automated test equipment, RF test equipment, defense, aerospace and other applications, which have high requirements for low insertion loss performance. In addition, in instrumentation, there is a demand for high bandwidth performance starting from DC. The perfect relay performance of ADI RF MEMS switches is very attractive to users, especially in automated test equipment, and has broad prospects.

Target Markets for ADI RF MEMS Switches

Eric said: "Typical applications in ATE are similar to filter switches. These switches require not only DC pass capability but also RF pass capability. It is difficult to find a good and clever switch solution for these requirements. Users generally use relays, but these relays often need to be replaced at a high cost due to life issues. The technical advantages of MEMS switches, including operation capability, wide bandwidth, small size, high linearity, and long life, just meet the needs of such applications."

Finally, I recommend you to watch this video. Eric introduced ADI RF MEMS switch technology in detail . P.S. It is nearly 40 minutes long. It is recommended to watch it in a wifi environment~