P9235A-R Datasheet

© 2016 Integrated Device Technology, Inc

17

May 17, 2016

Transmitter Resonant Tank Capacitors

For optimum performance, and to keep the characteristics of the resonant tank constant, the resonant frequency and quality factor must not

change due to variations in the associated capacitors or inductors. The capacitors of the resonant tank (C15, C17, C23, C25) must be

COG/NPO type only. COG/NPO capacitors have no temperature variation, less voltage related de-rating, and better accuracy than other

types of capacitors such at the X7R. Do not mix capacitor types when populating the resonant capacitors, use COG/NPO types only. All the

resonant capacitors must be rated for 50V. See the Bill of Materials for the recommended values.

Transmitter Resonant Tank Coils

Each half-bridge output connects to a series-resonance LC tank. The inductor serves as the primary coil of a loosely-coupled transformer; the

secondary is the receiver coil connected to the P9027LP-R.

The transmitter coils are mounted on a ferrite base acting as a shield to concentrate the field on the top side of the coil and to reduce EMI.

The coil assembly can be mounted next to the P9235A-R PCB or on the back of PCB. Either a ground plane or grounded metal shielding

(preferably copper) can be added beneath the ferrite shield for added reduction in radiated electrical field emissions. The coil ground

plane/shield must be connected to the ground plane by a single trace leading back independently to the board input power connector.

For optimum performance, the following coils are recommended for use with the P9235A-R transmitter for 1, 2 and 3 W applications. The

recommended coil vendors have been tested and verified to guarantee their performance.

Table 11. Coils Recommended with receiver for 1, 2 and 3 W Applications

Output

Power

Vendor

Part number

Inductance

DCR

Dimension

1W

TDK

WT151512-22F2-ID

6.49 uH

0.17 Ω

Ø15 mm

SunLord

SWA15T15H20C01B

6.30 uH

0.12 Ω

Ø15 mm

2W

TDK

WT202012-15F2-ID

6.20 uH

0.10 Ω

Ø20 mm

Wurth Electronics

760308101104

6.30 uH

0.11 Ω

Ø20 mm

SunLord

SWA20N20H20C01B

6.30 uH

0.15 Ω

Ø20 mm

3W

TDK

WT303012-13F2-ID

6.30 uH

0.12 Ω

Ø30 mm

Wurth Electronics

760308101103

6.50 uH

0.15 Ω

Ø30 mm

SunLord

SWA30N30H20C01B

6.25 uH

0.14 Ω

Ø30 mm

PCB Layout Considerations

Layout and PCB design have a significant influence on the system performance. The power dissipation capabilities of the P9235A-R surface

mount packaged power management IC rely heavily on thermally conductive traces and pads to transfer heat away from the package. The

regulator or full bridge inverter could show instability, as well as cause EMI problems, if the PCB layout is not designed properly. The following

general guidelines will be helpful in designing a board layout for low noise and EMI, as well as, the lowest thermal resistance:

1. PC board traces with large cross-sectional areas remove more heat. For optimal results, use large-area PCB patterns with wide

copper traces, placed on the component side of the PCB.

2. In cases where maximum heat dissipation is required, use double-sided copper planes connected with multiple vias.

3. Thermal vias provide a thermal path from the bridge FETs to inner and/or bottom layers of the PCB to remove the heat

generated by device power dissipation.

For more details, please refer to the application note AN936, “P9235A-R Layout Guidelines” for the layout details.