Traditionally, thermal performance of integrated FET drivers is difficult to manage for high power requirements. Since the power stage FETs are inside the package, it can be difficult dissipating the heat away. Gate drivers can handle higher current by selecting low R_DS(ON) external FETs.

However, with the latest adavances of the monolithic IC design techniques, integrated FET motor drivers from Texas Instruments can now push the boundary of maximum current and deliver output power much higher than was possible few years ago. By doing this, integrated FET drivers can replace external FET gate drivers - thereby delivering significant PCB area savings and external BOM cost reduction to customers.

In addition to using low on resistance of the integrated FETs, latest stepper motor drivers like the DRV8462 and DRV8452 also integrate advanced features to reduce power loss and maximize system efficiency even further. The DRV8462 and DRV8452 have the following features to reduce power loss and temperature rise of the driver:

• Auto-torque: Reduces output current when STEP pulses are being applied, but the load torque is lower than peak load.
• Standstill Power Saving Mode: Reduces output current when STEP pulses are not being applied.
• DDV Package: The DRV8462, DRV8262 and DRV8962 further support a DDV package option. The DDV package allows mounting a heat sink on top of the package, and therefore can reduce the thermal resistance of the package to ultra-low values.

Figure 2-5 to Figure 2-8 show the thermal images of the DRV8462 EVM at room temperature ambient for:

• DDW package at 24V, 5A, 1/16 microstep, 6 kpps speed; with and without auto-torque enabled
• DDV package at 48V, 10A, 1/16 microstep, 6 kpps speed; with and without auto-torque enabled

As seen in Figure 2-5 and Figure 2-7, without auto-torque, the DRV8462 IC and heat sink temperatures both exceed 100 °C. Moreover, the heat is concentrated in a small portion of the PCB - which makes it challenging to dissipate the heat away by increasing the PCB copper area or any other heat sinking method. With auto-torque enabled though, as seen in Figure 2-6 and Figure 2-8, temperature rise is minimal compared to the ambient temperature.

Figure 2-9 shows the thermal image for a DRV8711 EVM. Clearly the heat is spread out all over the PCB and concentrated over the external FETs, which makes it easier to cool down the solution by simple heat sinking methods.