ADP5003 / ADM7170 design check

I've been working on a power design using the ADP5003 and ADM7170.  I hope you will point out any flaws since I 've never done this before! Slight smile

Topology: The design uses the adaptive mode of the 5003 where the buck drives the LDO, converting 5V to 3V3 for the main power supply.  Switching frequency is 600KHz. The 7170 provides a dedicated 1v8 rail for an ADV7513 HDMI transmitter.

Load: 3V3 1150mA, 1.8V 200mA. (4200mW total)

Schematic: Here is the schematic.  I've simulated it in LTspice and it seems to work just fine, but let me know if anything absurd sticks out to you.

Thermals: Supplying 4.2W the 5003 should manage 85% efficiency according to the datasheet, giving a power dissipation of ~700mW.  The 7170 dissipates ~300mW.  This is the part of the design I know the least about - any advice welcome.

PCB: FR4, 102x72mm, 1.6mm thickness, 1oz copper, 6 layers.  Dedicated GND and 3V3 planes on layer 2 and layer 5, the rest are signal layers.

Can be changed to 1.2mm or 2mm thickness if it helps any.  Vias can be 0.2mm or 0.3mm diameter.

Layout: Pretty much the same as what is recommended in the datasheet.  The area shown in these shots is 32x36mm.

Red:       Top
Green:    Bottom
Blue:       GND
Fuschia: 3V3

There is nothing on the innermost signal layers in the power region. I could add copper fills there if you think it's a good idea.  Please mention if it's a bad idea too.

Here's a 3D rendering of the power section of the board to give some context, along with the component layout. Bottom fab layer is flipped.


Component selection:

As per the datasheet, except I replaced 0201 sized components with 0402.  I can't deal with any smaller than that. Slight smile

Power switch behaviour:

The 5V power supply is hardwired to the PVIN1 pins of the 5003.  When turned on the power switch connects +5V to the EN1 and EN2 pins. They have a 100K pulldown so they don't float when turned off.  Is this a reasonable configuration?  Normally I would have the switch directly control the physical power connection, but switches with a sufficiently high DC amperage rating are too big to use here.

3D image was shrunk down, reuploaded
[edited by: Eaz at 6:26 PM (GMT 0) on 19 Aug 2019]