P9415-R-EVK Evaluation Kit
R16UH0015EU0100 Rev.1.0
May 27, 2021
Page 15
7. TRx Wireless Power Coil
The TRx coil is dependent on customer requirements and most are custom designs. Renesas recommends the
following TRx coil as it was installed in P9415-R demo board.
■
Ls = 8 to 10
µ
H
■
DCR = < 0.3
Ω
■
ACR = < 0.4
Ω
Table 3. Coil Manufacturer
Output Power
Vendor
Part Number
Inductance at 100kHz
Resonant Caps
(Cs)
DC Resistance at
20
℃
15W
Luxshare
ICTR-QS5858031L-MW034
9.0
±
0.2
μ
H
400nF
195m
Ω
±10%
8. Resonance Capacitors
The series resonance capacitors (C32, C33, C34, C36, and C37) are critical components and must be chosen
carefully. All current that flows to the load flows through these components plus any current loss in the rectifier
AC to DC conversion. The recommended capacitor is the 100nF Murata (GRM155C71H104KE19, X7S, 50V, or
GRM155R61H104KE19, X5R, 50V), which have an ESR < 0.1ohms at 100kHz. The GRM155C71H104KE19
capacitor is the best choice based on ESR value and DC bias effects. If another capacitor is chosen, inspecting
the ESR vs. Frequency curve of the manufacturer’s capacitor datasheet is necessary to compare ESR
characteristics as well as the DC bias effects on the capacitor value. Adding non-populated (NP) component
placement (C37) is advised if the additional capacitance is needed for a particular Rx coil.
9. PCLAMP Connection
The P9415-R has an internal automatic DC clamping feature to protect the device from events that cause high
voltages to occur on the AC or DC side of the rectifier. The clamping engages by the VRECT connection to the
PCLAMP pin. The VRECT node must be connected to the PCLAMP pin at all times during Rx mode operation.
For greater than 5W operation, the VRECT node is connected to the PCLAMP pin using a 50Ω to 100Ω resistor
with greater than 1/4W rating with 2.5x or greater over-power surge capability. For space-constrained designs,
the PCLAMP pin can be directly connected to the VRECT node for 5W or lower power operation.
Also, there is an option for external FET and resistor clamping by the use of the ECLAMP_DRV pin which can
output 5V to drive the gate of external MOSFET. This output is synchronized with the internal PCLAMP signal.
ECLAMP_DRV can provide additional clamping capability as needed and there is no thermal increase in the IC
side because clamping energy is consumed in external components.
10. Transient Voltage Suppressors
The Transient Voltage Suppressor (TVS) is an active device that will direct high voltages from the input to
ground, thus protecting the wireless power device or other downstream ICs from being exposed to high voltages.
Transient Voltage Suppressor diodes should be added to the design from the AC1 and AC2 nodes to GND or
from AC1 to AC2. These components are useful to rapidly limit incoming ESD surges or situations when the TX
incoming power exceeds the expected power and VRECT voltage rises above target and Over-voltage
protection threshold in less than 10µs to aid in voltage limiting the incoming AC waveforms in conjunction with
the PCLAMP power limiting circuitry.
A balance in Reverse Standoff Voltage (VRWM), Clamping Voltage (VCL), Break-down Voltage (VBR) relative to
the expected VRECT operating voltage VRECT (be sure minimum VBR is less than maximum operating VRECT
value and that VCL is less than VRECT absolute maximum voltage) should be reached.
