IDT P9038, P9038-R-EVK Layout Manual

P9038 Layout Guide AN-894

APPLICATION NOTE

Contents

(Click on any of the headings below to jump to that section)

Using the Reference Layout ................................................................................................................2

Importing the Reference Layout .................................................................................................................. 2

Connecting a Power Source .........................................................................................................................3

Connecting Inputs / Outputs ......................................................................................................................... 3

Manufacturing Notes .....................................................................................................................................3

Additional Resources ....................................................................................................................................3

Custom Layout Guidelines ..................................................................................................................4

Layout Priority Checklist .............................................................................................................................. 4

Power Circuits ................................................................................................................................................5

Input Capacitors ...................................................................................................................................... 7

BST and ZVS Capacitors ........................................................................................................................9

EPAD ...............................................................................................................................................................11

Noise-sensitive Circuits ................................................................................................................................12

Non-sensitive Circuits ...................................................................................................................................13

PCB Footprint Design ...................................................................................................................................13

Thermal Performance ....................................................................................................................................14

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AN-894

Using the Reference Layout

The P9038-R-EVK reference layout is a simplified two-layer design optimized for high-performance, small-size, and ease-of-use.
Its purpose is to minimize design-in effort and risk by providing a proven solution that can be imported into an existing system
design. When circumstances permit, it is highly recommended to copy the reference layout. This will accelerate design time to
market at final product level.

Importing the Reference Layout

The P9038-R-EVK reference design was created using Cadence PCB design software. This software has been used to generate
layout modules which can be rapidly deployed onto PCB designs using Cadence OrCAD CIS and Cadence Allegro PCB Editor.
The P9038 Allegro layout module is labeled P9038-R-EVK.mdd and can be downloaded at www.idt.com/P9038-R-EVK
load into an existing or new PCB design file by following these instructions:

1. Use or copy the P9038-R-EVK schematic file (.dsn) and export the netlist to a PCB file.

2. Move the file P9038-R-EVK.mdd to the same directory as the PCB design file.

3. Import the netlist into the PCB file (.brd).

. It will

4. Open the PCB design file (.brd) and click on the menu Place

a. Select Place by Page Number and select the page the P9038 circuitry resides on.

→Quickplace…

Figure 1. Cadence Quickplace Option Box used for Placing the IDT Layout Module by Page Number

b. Click Place. Click Ok.

5. Select the parts that were placed from the schematic that matches the schematic used from the P9038-R-EVK.

a. In the Find Filter, select Symbols, then left click and drag to highlight all of the components that were just placed.

b. Right click on any of the highlighted parts and select “Place Replicate Apply

c. Select the P9038-R-EVK.mdd file and select Ok.

d. Components should be matched. If unmatched, manually identify and match component reference designators

based on schematic location.

6. Enter the coordinates (x,y location) in the command window where the P9038 circuit should be placed.

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→Browse…”

AN-894

Connecting a Power Source

The USB input connector accepts micro-USB cables type A or B. If a new design does not need this connector, simply extend
the VIN power trace and GND as needed to the location the new power connector will be placed at. If moving the power
connector is necessary, it is suggested to keep a solid GND plane leading to the new connector location and route VIN at a width
that is at least 100 mils wide as space permits.

Connecting Inputs / Outputs

All input and outputs on the reference board have been placed near the edges of the reference layout such that they can be
easily connected to other parts of the system board. After placing the module in the specific design, use the labeled vias as
connection points for new traces on either the top or bottom layer.

Manufacturing Notes

PCB should be made with a minimum of 1oz copper foil weight per square foot or heavier.

Additional Resources

All support files and collateral for the P9038-R-EVK reference board can be found at http://www.idt.com/P9038-R-EVK. Files
include: schematics, layout files, datasheets, user guides, etc.

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Custom Layout Guidelines

The P9038 wireless power transmitter is an integrated device consisting of a high power full-bridge inverter designed to drive
wireless LC resonance circuits and transmit power to WPC complaint wireless receivers. In addition to wireless power transfer,
there are noise sensitive circuits, General Purpose I/O's (GPIO's) and two low power linear regulators. When designing the
printed circuit board (PCB) there are multiple considerations and often some trade-offs associated with managing the critical
current paths. In order to optimize the design, components should be placed based on circuit function to guarantee best
performance when the schematic is implemented into a PCB design. Furthermore, the thermal management of the application
is important to the product's performance and should be optimized during PCB design. By following the guidelines set forth in
this document, efficient operation will be obtained for each circuit function.

Layout Priority Checklist

1. Place the Input capacitors and use short, wide connections from IN to PGND (target < 250mils long, > 50 mils wide).

2. Route SW1 and SW2 wide and short (use 6 – 10 vias for layer transitions) (target < 250mils long, >

3. Use wide planes (up to 2A) to route from the power connector to the R

4. Use sense (Kelvin) connections to connect to the current sense resistor R

5. Create wide continuous connections to the EPAD on bottom or internal PCB layer(s) (at least two 200 to 400 mil wide
channels should be directly connected to the EPAD and uninterrupted by traces for at least 1" leading away from the
IC). Use 25 thermal vias in the EPAD.

6. Place LDO capacitors as close as possible to the P9038.

7. Place Vsns Diode near LC and use 10 mils+ air gap separation from the cathode to the first filter resistor.

8. Place HPF capacitor near the P9038 and shield from switching side with shield resistor.

SENSE & IN and PGND connections.

SENSE. See Figure 9.

50 mils wide).

Figure 2. P9038 Simplified Diagram

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Power Circuits

The integrated Full-Bridge Inverter and the resonance tank are the primary power circuits. Secondary power circuits are the
LDO5V and LDO2P5V voltage regulators. After the connection points for the transmitter coil (LTX) are chosen, the P9038 should
be placed as close to the center of the PCB as possible with SW1 and SW2 pins facing the LC resonance tank. Components
should be placed in the following order of priority:

1. Input capacitors (C

IN)

2. BST1, BST2 capacitors

3. Resonance tank (C

P and LTX)

4. Zero Voltage Switching (ZVS) capacitors and tuning resistors

5. LDO capacitors

6. Current Sense Resistor (R

SENSE)

7. Optional USB input transistor (USB FET, see Application Note AN-867 P9038 OVP and In-Rush Current Limiting

Options for additional details)

8. Current sense filter components

Figure 3. P9038 Physical Layout from REFERENCE PCB (2 layer PCB), Main Power Sensitive Circuits

Figure 3 demonstrates the key nodes and layout recommendations for a 2-layer PCB. Important concepts include CIN direct

routing to IN and PGND pins and wide connections (>=60mils) for VIN. SWx nodes are routed on P9038 side of the PCB and
can easily be extended directly out for PCBs that have more distance to the edge of the board. LDO5V and LDO2P5V capacitors
are located very close to the IC with direct GND return to the EPAD. The EPAD has 25 thermal vias. Traces located on the bottom
layer have been placed as far as possible from the EPAD to create heat flow 'channels' (see the top left and lower regions
surrounding the EPAD on the bottom layer). Solid and continuous GND planes in direct contact with the EPAD will result in lower
operating temperatures and higher efficiency.

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