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TPS62901: Single-layer routing

Y.Ottey
Mastermind 6145 points
Part Number: TPS62901

Dear TI Team

I have something to check about TPS62901.
When I checked the following New product update materials, TPS6290x was introduced.

https://www.ti.com/lit/ml/slpp110/slpp110.pdf?ts=1618307145555&ref_url=https%253A%252F%252Ftraining.ti.com%252F

About the advantages of TPS6290x The document states that it can be implemented with a Single-Layer PCB layout.

I would like you to answer the following about this.

1. Is it correct to recognize that using TPS62901, it can be mounted with only a single layer including GND and heat dissipation parts?
(Usually, when mounting a DCDC, we think that it will be mounted using multiple layers as a measure against noise and heat dissipation. If it can be mounted with only a single layer, we think that the cost of the board will be greatly reduced.)

2. It is said that it can be configured with only a single layer. Is it possible to mount it on the back side of the component side, for example?
(I think that mounting with only a single layer means that it can be mounted on the back side of the surface on which other parts are mounted. This can reduce the board size.)

Best Regards,
Y.Ottey

  • +1
    TI__Mastermind 32350 points

    Hello Ottey,

    As shown in slide 16, single layer is possible. but that is depends on you system needs. The device itself does not require lot of external components and the pin out is well configured to support single layout if the user want to. That particular example shows a need to 1 input capacitor (10uF/25V) and 1 output capacitor (22uF/16V). The device is configured to 3.3V using VSET. So, only Mode/SCONF resistor is needed and VSET can be left open. The Mode/S-CONF resistor need to be connected to GND, so a GND trace can loop from the north to south of the board to reach SCONF resistor. That will require a long trace and that may cut off VIN or VOUT to do that. I am not sure if that will cause any issue with your outside connections.  EN can be connected directly to VIN, no pull up is required. For that, only 4 external components including the inductor are needed. Single layer is possible but depends on you system needs.

    Regarding your comment about thermal. Of course, more copper and inner layer will help dissipate thermal. For 1A thermal is not big challenge, you may end up managing with 1 layer, but that something you need to explore. You know your system needs and conditions …airflow, copper size, VIN, VOUT …etc.

    Mounting on the back side is possible with some possible side effect, I do not recommend it for the following reasons:

    • Having VIN, VOUT, SW going thru VIAS to reach the back of the board will add IR drop and thus will affect the efficiency and increase thermal rise.
    • VIN and VOUT need to be as close as possible to the pin, having them in the back side no satisfy this condition.
    • Also, you need to connect the VOS pin in the shortest way to VOUT at the output capacitor. otherwise the 1% accuracy cannot be achieved
    • Provide low inductive and resistive paths for loops with high di/dt. Therefore paths, conducting the switched load current should be as short and wide as possible. going thru vias is not going to help.

     

    Thanks!

    Tahar Allag