TSWITX-G4-EVM
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User Guide
Rev 1.00
Observe Coil Signals
The following information is not required in order to use the EVM, as what can be observed below is
entirely managed by the Semtech TS80002 Wireless Controller. However, it allows the observer an
opportunity to see how the receiver and transmitter actively manage the wireless power process.
If you wish to observe the intrinsic wireless process, place an oscilloscope probe on one antenna lead,
with the probe ground run to the board ground (the outer casing of the USB port will suffice). Be sure the
scope can handle signals up to 100 volts. While the EVM power supply is only 5 volts, the antenna is part
of a resonant circuit where considerably higher voltages are developed.
To observe the search ping, apply power to the transmitter and remove the receiver from the target zone.
The scope should display a ‘chirp’ of 0.5 to 1mSec in duration with an initial peak of 30 to 35 volts. The
frequency within the envelope of the chirp is in the 1-1.15 MHz range.
Next, place the receiver on the transmitter target. With the scope set to 0.2 to 1 uSec and 2 to 10 volts
per division, you should observe a ‘fuzzy sinewave’ signal that is a composite of the sinusoidal power
signal with an additional component produced by the much lower frequency digital communication
between the receiver and transmitter. Observing the signal in the 1 to 5 mSec range will allow the ability
to see the digital signal riding on the power modulation more readily. Note as you vary the load and the
location of the receiver on the target that the amplitude and frequency of the coil signal changes. The
greater the load, the more signal is sent to transfer the power required by the load. Similarly, the less well
coupled the receiver antenna is to the transmitter coil, the more power must be sent to compensate for
the inefficient misalignment. You may note in excess of 50 volts peak-to-peak in the most demanding
conditions.
Measure Efficiency
By measuring the power from the receiver’s VOUT+ and GND pins in comparison to the power entering
the transmitter EVM, you can determine the efficiency of the power transfer through the system. The
diagram below was obtained from the TSWITX-G4-EVM and TSWIRX-5V2-EVM. When measuring
efficiency, be sure to remove the jumpers on the receiver and transmitter that enable the status LEDs, as
these will affect the measurements.
0.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
0
m
A
1
0
m
A
2
0
m
A
3
0
m
A
4
0
m
A
5
0
m
A
6
0
m
A
7
0
m
A
8
0
m
A
9
0
m
A
1
0
0
m
A
1
1
0
m
A
1
2
0
m
A
1
3
0
m
A
1
4
0
m
A
1
5
0
m
A
1
6
0
m
A
1
7
0
m
A
1
8
0
m
A
1
9
0
m
A
2
0
0
m
A
2
1
0
m
A
2
2
0
m
A
2
3
0
m
A
2
4
0
m
A
2
5
0
m
A
Efficiency vs Load
