Wireless Charging
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User Guide
Rev 1.03
TSDMRX-19V20W-EVM Semtech
Connect a DC voltmeter across the VOUT+ and - pins to monitor the voltage being output to the load, and a DC
ammeter in series with the VOUT+ line. Set levels to allow for up to 20 volts and 1.5 amps to be observed.
With no load selected, place the receiver on the center of the transmitter target circle. Once transmission begins,
you should observe approximately 19 volts and 0 amperes on the meters.
Apply a variety of loads to observe performance at 20 watt levels. Voltage should remain nearly constant, and
current should follow the P=V*I relationship. Experiment with the maximum power that can be drawn before the
receiver detects an overload and cuts off power. You should be able to observe on a minor overload, the receiver
will attempt to restore power by retesting the load intermittently. In the case of a major overload, the transmitter
may register an error, as indicated by a red LED on the transmitter, which will halt further activity until the receiver
is removed from the target area for several seconds before being returned to start a new transaction.
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 TS81000 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 the antenna leads, with the
probe ground run to the board ground. Be sure the scope can handle signals up to 200 volts. While the EVM power
output is only 19 volts, the antenna is part of a resonant circuit where considerably higher voltages are developed.
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.
