TPS61089: PCB layout advice

Dharmesh Joshi

Part Number: TPS61089

I am using the TPS61089RNRR to generate 9V 1.5A from a 4.2V 2000mAH Li-poly battery. Once the 9V is generated i am powering the DRV8870DDAR, to control the required solenoids.

Please find my schematic and PCB layout below.

I would like to know:

1. VCC_4V2 is 4.2V. It is directly connected from the battery to the VCC layer. From the VCC layer, to comes to the TOP layer copper pour using the 17 vias shown. Would this be an efficient way of doing this or should there be more vias?

2. The 9V is outputted onto a copper pour on the top layer, which is then used by the DRV8870DDAR?

3. The copper pour are all on the TOP layer only, should a identical copper pour also be placed on the bottom layer, with multiple vias?

I would appreciate if someone could kindly have a look into this Layout for any possible issues?

Thanks

over 6 years ago

0 Helen chen over 6 years ago

TI__Mastermind 40080 points

you can put all the copper on the top layer except the GND copper, please pour a big GnD copper plane at the bottom layer. And put a via on the TPS61089's GND pin, this vias helps the thermal.

0 Dharmesh Joshi over 6 years ago in reply to Helen chen

Expert 1815 points

Dear Helen

I will add a GND via on the GND pin of the device.

As suggested "you can put all the copper on the top layer except the GND copper" my top layer has GND pour as this is necessary for my RF design. Can you please explain what you mean?

YES the on the picture i posted, i disabled the bottom layer. But bottom layer is also a GND copper pour as well. Therefore the via connect top, bottom and GND layer all together.

0 Helen chen over 6 years ago in reply to Dharmesh Joshi

TI__Mastermind 40080 points

Sorry for the confusion. What I mean is you need to pour GND copper plane on the bottom layer as well. But for the other net like Vout, Vin, SW , put these net's copper plane on top layer is enough.

0 Dharmesh Joshi over 6 years ago in reply to Helen chen

Expert 1815 points

Ok , that is what i have done now.

Does the size of the via have any effect?

Is the copper pour on VIN ok, as there are many vias going to the VCC layer.

0 Helen chen over 6 years ago in reply to Dharmesh Joshi

TI__Mastermind 40080 points

If all the input current is supplied by the Vcc throgh the vias, then please make the via size larger. you can use 40mil via hole size.

0 Dharmesh Joshi over 6 years ago in reply to Helen chen

Expert 1815 points

Hi Helen

Thanks.

My via are 0.6 with 0.4mm.

I am now thinking about changing the oritiantion of the DC-DC on the PCB, so that the VIN is close to battery terminal. Therefore using a small copper track or pour i can have the input current come to the DC-DC without the VCC layer.

The VCC layer will still be there but current will flow on the top layer as well, therefore via as well as a top copper pour will be used.

This PCB shows, the copper pour from P5 (VCC) connecting to the DC-DC