Installation Instructions

ADI Confidential
Rev. Sp0 | Page 11 of 20
VITAL SIGNS MONITORED
To minimize the power line interference (50 Hz/60 Hz) and
improve the quality of the output signal, it is recommended
to use the BLE link.
PHOTOPLETHYSMOGRAPHY (PPG)—
ADPD4100
The ADPD4100 operates as a complete multimodal sensor
front end, stimulating up to eight LEDs (four on the VSM
Watch) and measuring the return signal on up to eight
separate current inputs. Twelve time slots are available,
enabling 12 separate measurements per sampling period.
The data output and functional configuration utilize an I2C
interface on the ADPD4001 or a serial port interface (SPI)
on the ADPD4000. The control circuitry includes flexible
LED signaling and synchronous detection. The devices use a
1.8 V analog core and 1.8 V/3.3 V compatible digital
input/output (I/O).
Refer to the ADPD4100 product page and data sheet for
further details.
Details regarding the hardware implementation are found
in Table 4 and Table 5.
Table 4. Electrical Connections to the ADPD4100 Inputs
Input
Pin
Description
IN-1
VEMD8080 Photodiode 1
IN-2
IN-3
IN-4
IN-5
IN-6
IN-7
IN-8
VEMD8080 Photodiode 2
Temp Sensor
Temp Sensor
ECG / Bio-Z
ECG / Bio-Z
ECG / Bio-Z
ECG / Bio-Z
Table 5. Electrical Connections to the ADPD4100 LED
Current Sinks
Current Sink
Color
Wavelength
No. of LEDs
LED1A
Green
530 nm
1
LED2A
Infrared
850 nm
1
LED3A
LED4A
Red
Blue
660 nm
470 nm
1
1
MOTION AND ACTIVITY - ADXL362
Motion is sensed by the ADXL362, an ultra-low power, 3-
axis, ±2 g/±4 g/±8 g digital output high resolution (1
mg/LSB) accelerometer. Its power consumption is 1.8 µA at
100 samples per second (SPS) and 3.0 µA at 400 SPS, while
its motion activated wake-up mode only requires 270 nA.
A pedometer algorithm is embedded for evaluation that can
be enabled in Wavetool.
ELECTROCARDIOGRAPHY - AD8233
The AD8233 is a 50 µA 2.0 mm × 1.7 mm WLCSP low noise
single lead analog output biopotential front end.
Integrated ECG Electrodes
The AD8233 is connected to the electrodes hosted in the top
and bottom surfaces of the watch. The two electrodes on the
top of the watch are connected to IN− pin and RLD pin, while
the two electrodes on the bottom of the watch are shorted
together (temporarily while this measurement is active) and
connected to the IN+ input.
The quality of the contact of the bottom electrodes has a
dramatic effect on the output waveform. Dry, hairy skin
poses a challenge for this measurement until moisture
accumulates between the skin and the electrodes. This
usually happens a few minutes after the user puts on the
device. Accumulated moisture decreases the contact
impedance and, therefore, the quality of the output
waveform improves.
The configuration of this signal chain is similar to an
ambulatory ECG device (Holter monitor).
Table 6. Electrical Specifications of the ECG Signal
Chain
1
Specification
Value (typ)
Unit
Passing
Bandwidth
0.4 to 42
Hz
High-Pass Filter
First Order
N/A
Low-Pass Filter
Second order (quality factor
= 0.671)
N/A
AD8233 Gain
151
V/V
ADC Resolution
16
bits
Noise RTI
TBD
µV p-p
Sampling Rate
50 to 1000
SPS
1
N/A means not applicable.
External ECG Cables
The charging cradle provides a secondary micro-USB
connection to be used with external wired electrodes.
BIO-IMPEDANCE – AD5940
Impedance is measured using the AD5940 Impedance AFE.
Proper electrical contact between these two electrodes and
the skin is critical for accurate and reliable long-term
measurement. Adequate tightness of the watch strap helps
achieve a proper contact and wearing the watch beside (but
not on top of) the ulnar styloid process (the protruding
wrist bone) also helps ensure a reliable and high-quality
measurement.
Note that these two electrodes are also used by the ECG
measurement, which temporarily shorts them together.