Flash is limited to approximately 10,000 write
cycles while FRAM write
cycles are in the billions.
FRAM can be used in
true data-logging appli-
cations where data needs
to be retrieved when
system power is lost. To
define the difference in the energy efficiency of the two memory
technologies, we use the device parameters listed in Table 3 and
calculate the battery lifetime of a bio-patch where the sensor data
is logged, accounting for the erase cycle of the Flash memory in the
calculation and maintaining the RF duty cycle.
As can be seen in Figure 4, data logging using FRAM does not
impact the overall battery lifetime even for the case where the
sensor is collecting 32 bytes of memory for the given sensor cycle.
But, Flash results in a significant drop in the battery lifetime of the
bio-patch — up to 30 percent for 32 bytes of sensor-collected data.
Signal chain and conditioning of the bio-patch
To finalize the signal chain of the bio-patch solution we look
at the impact of the signal conditioning on the overall power
efficiency calculation. Driving the adaptive signal conditioning
to the analog front end prior to the analog to digital conversion
(ADC) reduces the computational requirements of the MCU and
also minimizes the on time of the processor. As an example, we
take a look at the sensor response of a typical electrocardiogram
(ECG) signal shown in Figure 5. The superimposed transients
drive a requirement for an ADC with a higher resolution had
the transients been removed prior to sensing with the ADC. The
power performance of a 14-bit successive approximation (SAR)
ADC is significantly better compared to a 22-bit SAR ADC.
An optimization of the power efficiency is carried out by an
understanding of the different system components that make up
the total signal chain of the bio-patch solution in relation to the
specific use case. For continuous monitoring solutions, we see
that the RF component drives the overall system lifetime. For
semi-continuous or ‘on-demand’ solutions with lower RF duty
cycles, the other components of the signal chain contribute a significant share of the complete power efficiency breakdown. ECN
Figure 4. System battery lifetimes for aggregated data logging system
solutions (FRAM versus Flash).
Tprogram FRAM 100e- 9 sec
Iprogram FRAM .85 mA
Tprogram Flash 100e- 6 sec
Terase 20e- 3 sec
Table 3. Memory data logging parameters.
Figure 5. Typical ECG signal highlighting periods of significant
change in the response.
Modules designed for use in delivery trucks
Telit Wireless Solutions and Tritavia SA de CV (Tritavia)announced that SIAF (Sistema Integral de
Administración de Flotillas), Tritavia’s cellular-connected fleet management system uses Telit’s GE865-
QUAD GSM/GPRS cellular module for wireless data communications. The company’s fleet management
system meets the operating requirements and integrates the business processes for a leading Mexico-based soft-drink distributor and one of the world’s largest. Tritavia uses a Web portal to allow delivery coordinators to continually improve productivity and track the movement of the company’s soft-drink delivery
truck-fleet. Telit’s GE865-QUAD used in the SIAF is ideal for size sensitive and high-volume applications.
Valuable features, including on-board Python interpreter and Over-The-Air firmware update, make this
product an efficient solution for most M2M market segments. The BGA packaged module is well suited for
embedded cellular applications where small size and energy efficiency are crucial in mobile and fixed application areas such as security and surveillance, vending, point-of-sale (POS), tracking, smart metering, and
Telit Wireless Solutions, www.telit.com