RF module for implantable medical device designers

Paul Boughton

Microsemi Corporation has announced the availability of the smallest radio module it has ever produced.

The ZL70323 is optimised for implantable medical devices such as pacemakers, cardiac defibrillators and neurostimulators—measuring just 5.5mm x 4.5mm x 1.5mm. The new radio module supersedes the company’s ZL70321 and complements its ZL70120 radio module used for external device controllers. Both modules are based on Microsemi’s industry-leading ultralow power (ULP) ZL70103 radio transceiver chip, which supports a very high data rate radio frequency (RF) link for medical implantable communication applications.

RF technology is increasingly being used in a wide variety of medical implantable applications including cardiac care, physiological monitoring (eg, insulin), pain management and obesity treatments.

According to Roots Analysis Business Research & Consulting, the global neurostimulation devices market is likely to achieve sales of $6.5 billion by 2017, growing at a compounded annual growth rate (CAGR) of 17.9% from 2011 to 2017.

The ZL70323 implantable module implements all RF-related functions needed to deploy the implant node in a Medical Implantable Communications Service (MICS) RF telemetry system. The integrated antenna tuning circuit allows the module to be used with a wide range of implantable antennas (nominal antenna impedance is 100+j150 ohms). The module provides the following major blocks:

* L70103-based MICS-band RF transceiver with integrated matching network, surface acoustic wave (SAW) filter for suppression of unwanted blockers, and antenna tuning;

* 2.45 gigahertz (GHz) wake-up receiver matching network;

* Integrated 24 megahertz (MHz) reference frequency crystal; and

* Decoupling capacitors and series termination resistors.

Microsemi’s ZL70103 family of products allows patient health and device performance data to be quickly transmitted with little impact to the battery life of the implanted device. The device operates in the 402–405 MHz MICS band. Multiple low power wake-up options are supported including using an ULP 2.45 GHz industrial, scientific and medical (ISM) band wake-up receive option. The ZL70103 consumes less than 6 milliamperes (mA) when transmitting or receiving and consumes only 290 nanoamperes (nA) when in a periodic sleep/sniff mode (1 second sniff interval).