Wireless Charging
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User Guide
Rev 2.0
TSDMRX-5W-EVM
Jun 2016
Semtech
If using the USB port, power is provided via pin 1 (VBUS) and pin 4 (GND). Otherwise, run wires from the
VOUT+ and VOUT- pins of the receiver EVM to the selected test load, as per the illustration above. Once
the load is added, the receiver EVM can be used to perform a variety of tests.
Connect a DC voltmeter across the VOUT+ and VOUT- 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 10 volts and 2 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 5 volts and 0 amperes on the meters.
Apply a variety of loads to observe performance between 0 and 5 watts. 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 right-most J1 pin
(an antenna lead), with the probe ground run to the board ground on VOUT-. Be sure the scope can
handle signals up to 200 volts. While the EVM power output is only 5 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. You may note voltages near 140 volts peak-
to-peak in the most demanding conditions.