Powering wireless medical instrumentation requires the right approach: Page 3 of 4

January 30, 2017 // By Tony Armstrong
Powering wireless medical instrumentation requires the right approach
As with many applications, low power precision components have enabled rapid growth of portable and wireless medical instruments. However, unlike many other applications, many medical products typically have much higher standards for reliability, run-time and robustness. As you would expect, much of this burden falls on the power system and its associated support components.

In addition, the device’s integrated precision (±5% battery discharge measurement accuracy) coulomb counter provides accurate monitoring of accumulated battery discharge in long-life non-rechargeable battery-powered applications which in many cases have extremely flat battery discharge curves. The LTC3335 includes four internal low RDSON MOSFETs and can deliver efficiencies of up to 90%. Other features include a programmable discharge alarm threshold, an I2C interface for accessing coulomb count and device programming, a Power Good output, and 8 selectable peak input currents from 5mA up to 250mA to accommodate a wide range of battery types and sizes. The LTC3335 is available with an operating junction temperature range from -40°C to +125°C in a thermally enhanced, 20-lead 3x4mm QFN package.

Another way to get a combination of low voltages rails from a DC input of 24V or 12V is to use a high voltage DC/DC converter with multiple output capabilities. Therefore, Linear Technology developed its 4 output monolithic synchronous buck converter, the LT8602. Its 3V to 42V input voltage range make it ideal for medical applications. As can be seen in Figure 2, its quad channel design combines two high voltage 2.5A and 1.5A channels with two lower voltage 1.8A channels to deliver four independent outputs delivering voltages as low as 0.8V, enabling it to drive the lowest voltage microprocessor cores currently available. Its synchronous rectification topology delivers up to 94% efficiency while Burst Mode® operation keeps quiescent current under 30µA (all channels on) in no-load standby conditions making it ideal for battery operated systems.

Fig. 2:  LT8602 schematic delivers 5V, 3.3V, 1.8V & 1.2V outputs.

For noise-sensitive applications, the LT8602, with a small external filter, can utilize its pulse-skipping mode to minimize switching noise and can meet the CISPR25, Class 5 EMI requirements. This enables it to be used readily in systems that incorporate wireless transmission of data.

Design category: 

Vous êtes certain ?

Si vous désactivez les cookies, vous ne pouvez plus naviguer sur le site.

Vous allez être rediriger vers Google.