TSDMTX-19V2-EVM Datasheet, PDF (9/22 Pages) –

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 TS80000 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 (one of the fastener screws will suffice). Be sure the scope can handle
signals up to 200 volts. While the EVM power supply is only 19 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 15 to 20 volts. The frequency
within the envelope of the chirp is in the 100-150 kHz range, which is the normal range of Qi and PMA systems.
Next, place the receiver on the transmitter target. With the scope set to 0.5 to 1 uSec and 10 to 20 volts per
division, you should observe a signal that is a composite of the sinusoidal power signal with a digital ‘notch’ in
the sinewave which is produced by the communication between the receiver and transmitter. 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 voltages near 140 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. For the EVMs used
here, the diagram below demonstrates that efficiency is a function of output current, and runs about 75% at
higher power levels, assuring good efficiency and minimal heat dissipation concerns.
L^oo^aa^dd ^Vv^Ss ^eE^fffⁱi^cc^ieieⁿn^cc^yy
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7
Out^op^uu^tpt^uC^{t c}u^urr^eeⁿn^t(t^A(⁾A)
Wireless Charging
User Guide
TSDMTX-19V1-EVM
Rev 1.01
Feb 2016
www.semtech.com
7 of 19
Semtech