TLV767-Q1: The thermal pad layout question

Pin Tsai (TW FAE)

Part Number: TLV767-Q1

Hi Expert,

My customer is using tow TLV767-Q1 in the 12V->5V and 5V-3.3V. Here is the layout. They use the 4 layers board, and the picture is layer 4. The via is connected to layer 3 which is the ground plane.

Regarding to the thermal consideration, customer has questions below

1. Is that necessary to place the via under thermal pad? Or it's better route to GND_PIN then through via to layer 3?

2. As mentioned above, there are two TLV767-Q1. Do they need to route the GND of two devices to single via to avoid the noise? Or it is ok to have two via for each LDO to connect to ground plane (layer 3).

3. Is there any portion need to be modified in customer's current layout?

Thank you!

over 2 years ago

0 Pin Tsai (TW FAE) over 2 years ago

TI__Intellectual 2290 points

Hi Team,

Can you help to move this thread to internal?

Thank you,

0 Stephen Ziel over 2 years ago in reply to Pin Tsai (TW FAE)

TI__Mastermind 29320 points

Hi Pin,

In general, a handful of thermal via's is always better than 0, or 1. If the desire is to dissipate heat from the LDO, then you want the thermal via directly underneath the LDO in the thermal pad. The thermal pad is designed to dissipate heat, while the GND pin is designed to have a low impedance path to GND on the internal die.

The layout from the customer looks good to me. I would use 2 thermal via's over 1 via. The noise should not be a significant issue.

Thanks,

Stephen

0 Pin Tsai (TW FAE) over 2 years ago in reply to Stephen Ziel

TI__Intellectual 2290 points

Hi Stephen,

Thank you!

So, the thermal pad is not electrically connected to GND, right?

BR,

+1 Stephen Ziel over 2 years ago in reply to Pin Tsai (TW FAE)

TI__Mastermind 29320 points

Hi Pin,

The thermal pad is connected to GND but it may not be a low impedance connection to GND. The job of the thermal pad is to dissipate the heat, as opposed to providing the low impedance to GND connection - that job is given to the GND pin.

Thanks,

Stephen

Power management

Power management forum

TLV767-Q1: The thermal pad layout question