Application Note AN-91

BridgeSwitch Family

www.power.com November 2020

Triangular PCB vs. Slotted Linear PCB Conguration

for Three-Phase Inverter Applications

Introduction

For 3-phase inverter applications, each InSOP-24C surface mount

package dissipates a third of the total inverter losses. The heat

distribution allows the construction of a motor drive without an

external heat sink. Two exposed pads facilitate heat transfer from the

power switches to the printed circuit board (PCB). They are marked

HD and HB in Figure 1.

LS 24 1 XL

2 IPH (NC)

3 SG

4 BPL

HB 16-19

XH 13

BPH 14

NC 15

5 INL

6 /INH

7 FAULT

8 SM

9 NC

10 SG

11 ID

12 NC

PI-8292a-050719

Figure 1. BridgeSwitch InSOP-24C (Bottom View).

The thermal performance is affected by the placement of the devices,

the distance between them, the size of the copper-clad areas

connected to the exposed pads, and the thickness of the copper used

for heat sinking. In the PCB congurations previously evaluated for the

whitepaper, “Impact of Printed Circuit Board Layout on Device

Temperature in 3-Phase Inverters Using BridgeSwitch” (ht tps://

motor-driver.power.com/design-support/articles/impact-of-printed-

circuit-board-layout-on-device-temperature-in-3-phase-inverters-using-

bridgeswitch/), the results show an increase in the device case

temperatures for the linear PCB conguration as seen in Figure 3.

Due to the heat converging at the center, the middle device exhibits a

higher case temperature compared to the adjacent devices.

The linear PCB conguration offers a smaller and more compact PCB

layout that is desirable for some applications. Slots were added

between the BridgeSwitch devices to maximize the advantage of the

linear device placement resulting in the slotted linear PCB conguration

in Figure 4. This addition will prevent the heat from the adjacent

devices from affecting the temperature of the middle IC.

vias

2*D

Linear

Triangular B

Triangular A

PI-8972-051519

Figure 2. Linear, Triangular A, and Triangular B Device Congurations.

Note: A = PCB copper area, D = distance between devices

Rev. A 11/20

Application Note

www.power.com

AN-91

a) Triangular A Configuration,

D=17 mm, A=600 mm²

b) Triangular B Configuration,

D=17 mm, A=600 mm²

c) Linear Configuration,

D=17

mm, A=600 mm²

Figure 3. Thermal Device Scans (Triangular A, Triangular B, and Linear Congurations).

Scope

This application note compares the thermal performance of the

triangular PCB conguration to the slotted linear PCB conguration

with regards to case temperature rise above ambient temperature

and temperature variations between adjacent BridgeSwitch devices

using BridgeSwitch reference design boards.

It includes the following sections:

• Layout Revision

• Test Conditions

• Test Results

• Triangular PCB Conguration

• Slotted Linear PCB Conguration

• PCB Conguration Comparison

• Conclusion