Biomedical Engineering Reference
In-Depth Information
LTC6081
INA321
LTC6081
Fig. 5.19
Analog front-end of the sensor node
5.2.7 Analog Front-End
The analog front-end of the sensor node is designed to amplify low voltage
physiological signals, such as ECG. ECG signals generate a waveform with peak
amplitude of approximately 500 lV and a frequency of 100 Hz. During the first
stage of the front-end, low voltage, analog input signals are amplified by 14 dB
using the INA321 instrumentation amplifier [
19
]. The second stage of the front-end
acts as an active LPF with a cut-off frequency of 100 Hz and a gain of 46 dB. This
is implemented using LTC6081 precision dual output amplifier [
10
]. These com-
ponents are selected for the analog front-end mainly due to their high common
mode rejection ratio. The schematic of the analog front-end is depicted in
Fig.
5.19
.
5.2.8 Power Supply Management
The LP5996 dual linear regulator [
19
] regulates the power to the sensor node. RF
portions of the circuit are powered using a 3 V regulated power line while rest of
the circuit is powered using a 3.3 V supply. Power to each individual section of the
circuit can be independently controlled by the micro-controller, leading way to
power efficient operation of the sensor node. All the power supply pins of the
sensor node are connected to the power plane of the PCB using vias.
