Semtech Unveils Chip That Eases 5G Mobile Device Compliance

One of the most dreaded aspects of designing any electrical system is passing compliance. Depending on the nature of the device, compliance can encompass many different things, but at its core, all compliance tests want to ensure the safety of people and electrical devices that are nearby your device.

One field where compliance is particularly important is the wireless communication industry. Specifically, wireless devices must all pass Specific Absorption Rate (SAR) testing to ensure that a user’s RF exposure is kept below an acceptable limit.

 

The PerSe Connect SX9376 seeks to improve 5G performance while easing SAR compliance. Image used courtesy of Semtech

 

With all that in mind, last week Semtech released its PerSe Connect SX9376 IC. The chip is designed to help ensure that 5G devices are able to balance 5G performance with SAR compliance. In this article, we’ll take a look at SAR compliance and how Semtech’s new IC hopes to help 5G designers.

 

Understanding Specific Absorption Rate Compliance

For cellular devices, one of the most significant compliance metrics is that of Specific Absorption Rate (SAR). To understand SAR, we first understand that as part of their operation, wireless devices emit intentional RF signals as a means of communication.

Depending on the frequency of the emitted signal, the tissue and other constituents of the human body are capable of absorbing this emitted RF energy. To help limit exposure to RF energy that could cause bodily harm, the FCC regulates the amount of Specific Absorption a device should be able to cause.

 

An SAR compliance testing setup. Image from EMF Explained

 

As defined by the FCC, SAR is a value that corresponds to the relative amount of RF energy absorbed in the head of a user of a wireless handset. Per FCC guidelines, the limit for SAR exposure by cellular telephones is capped at 1.6 watts per kilogram (1.6 W/kg).

To achieve compliance with SAR limits, cellular device companies often have to intentionally limit the output power of their RF hardware. While this helps ensure safety, it also has a detrimental impact on performance, limiting the range and reliability of a cellular link.

 

PerSe SX9376 for 5G Mobile Designs

The new PerSe Connect SX9376 device expands Semtech’s existing PerSe product portfolio. The company says the SX9376 is designed specifically for ensuring that 5G mobile devices can balance the tradeoffs of maintaining SAR compliance while maintaining performance. Semtech says it offers a datasheet for the chip, but access to it requires registration.

To do this, the chip features a unique on-chip human sensing element that can determine the presence of a person near a cellular handset. From here, the SX9376 offers an 8-channel sensor input to support advanced RF control of multiple antennas simultaneously.

Part of this architecture includes a high-resolution analog front end with a capacitance resolution down to 0.74 aF. A unit not seen very often in engineering circles, “aF” stands for attofarad, which is an electrical capacitance of 10^-18 farads.

 

Circuit diagram example using the SX9376. Image used courtesy of Semtech

 

By communicating human presence data to the host via an integrated I²C serial interface, the SX9376 allows for the RF system to dynamically change its output power. For example, if a human is detected present, the device can decrease its output power and vice versa. In this way, Semtech’s new IC makes it possible to keep humans safe while also allowing mobile devices to ensure greater range and reliability.

In addition to all of the integrated features, Semtech’s new chip operates down to 1.8 V, making it a welcome option for low-power solutions—an important feature for a battery-powered mobile device. Altogether, Semtech believes its new IC can have a significant impact on the growing 5G hardware market.