Ultra low-power RF CMOS ISM transmitter

The real world problem

Transmit only remote wireless sensor devices have found many unique applications in the Medical, Industrial and other markets, for instance:

• Active RF IDs
• Battery-less wireless switches and sensors
• Tyre pressure monitoring systems
• Wireless healthcare monitoring: EEG, EMG, ECG, and oximeter
• Swallowable, non-invasive, endoscopy camera
• Wireless alarm and security systems
• Automatic meter reading

 To enable many of these markets an ISM transmitter that can operate for months or even years using a single cell battery is required.

The solution

To service these applications AnSem developed an ultra low-power RF ISM transmitter in 0.25µm CMOS with an active power consumption of 2.6mW - 10 times lower than any other product available today. The transmitter's low operating voltage - as low as 0.9V - and wide supply voltage range makes it possible to power it from a single alkaline battery. Further, the combination of low voltage and low power consumption enables battery-less applications, e.g. solar cells or other energy scavenging methods.

The RF ISM transmitter supports 2-FSK modulation with a programmable data rate from 900bps → 128 kbps. It also features a programmable data buffer depth from 1 byte up to 128 bytes in steps of 1 byte. Power saving optimization is achieved using the built in burst mode functionality; the device consumes less than 1 µA in standby. An integrated Serial Peripheral Interface (SPI) makes the transmitter flexible and easy to use. An entire module based on the device fits into 1 cubic centimeter - including controller and external components - making it well suited for all kinds of portable applications.

Key technical statistics

• Power supply 0.9 V → 1.6 V
• Power Consumption:
  - Fully active = 2.6mW @ Pout = -10dBm, (1.3V)
  - standby-mode < 1µA (less than battery leakage)