Switching Regulator Layout - GND connection?

[Phoenix2k]

Hi guys,

I'm working on a board consisting of two switching regulators and some analog stuff. The voltage generated by the two regulators is connected to another board using connectors and a cable.
I already read some papers on PCB layout regarding buck/boost converters and just wanted to know your opinion on my concept.

The board is a two-layer PCB, my plan was to place the boost converter, the buck converter and a PWM regulator (Fan control) on the top layer in one corner and the analog circuitry (amplifier, temp regulation, ...) in the opposide corner.
The two regulators and the PWM GND should be connected with a Power-GND rail/polygon on the top layer. The bottom layer serves as AGND plane.
The devices in the high current path (Inductor, diode, mosfet, bypass capacitors) will be placed as close as possible on the respective regulator IC's.

Where do you think is the best place to connect Power-GND and AGND:?:
At the moment I would make a connection between the top Power-GND-rail and the AGND plane at the bypass-capacitor of the first regulator.
Another question is whether I connect the GND from the input-supply to Power-GND or to the AGND-plane:?:

Greetings
Phoenix2k

 

[asimlink]

It is difficult for me to comment on component placement without lookint at your board and component datasheet. I would suggest you to follow following guidelines for your power supply pcb design:

https://www.smps.us/layout.html

Also read:
AN-1149 Layout Guidelines for Switching Power Supplies (Rev. B)
www.ti.com/lit/an/snva021b/snva021b.pdf

Regards