There are many factors to consider when selecting motor drivers, and one of the most important is deciding between integrated FETs or external FETs for the power stage. Integrated FET drivers reduce solution size and number of external components in the bill of materials, but the thermal performance of gate drivers is generally superior. With recent advances in semiconductor technology, integrated FET drivers from Texas Instruments are now able to support higher power requirements than ever before and can replace external FET gate drivers in many applications. This application report serves as a guide to explain the differences between integrated FET drivers and external FET gate drivers, comparing traditional motor driver solutions for high power against few recently released integrated FET drivers from Texas Instruments in regards to solution size, bill of materials, and thermal performance.
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In this topology, the power stage FETs and the FET controller are in different IC packages. Figure 1-1 shows the block diagram of a brushed-DC motor driver circuit with a controller chip, along with four external FETs. This arrangement allows the designer to select the controller and the FETs independently.
Gate drivers generally require more number of passive external components, and gate driver circuit design might involve a number of iterations so that the performance can be optimized.
A motor driver with an integrated FET means the power stage FETs are included inside the driver package, as Figure 1-2 shows. Integrated FETs minimize the design effort needed to get started with a motor drive application, as the FET characteristics are already selected to match the requirements of the specified motor current.
The integrated FET topology has been traditionally used for low to moderate motor current applications - for example, brushed-DC motors up to 10 A peak current and stepper motors up to 3 A full-scale current. The maximum current was primarily limited by the lowest possible on resistance of the FETs that could be integrated in the same monolithic die - it was difficult to integrate on resistance less than 300 mΩ if the voltage rating of the driver was close to 40 V or higher. For applications that needed higher currents, external FET gate drivers were used.
However, with recent innovations in analog process technologies, IC design and packaging technologies, latest integrated FET drivers from Texas Instruments are now capable of driving significantly higher current at a higher supply voltage. This is done by reducing the on resistance of the integrated FETs to 100 mΩ or lower. As shown in Table 1-1, several high-power integrated FET motor drivers for industrial and automotive applications have been introduced. These integrated FET motor drivers can replace external FET gate drivers which were the preferred solution for high power motor driver systems so far.
Device | Type | Maximum Operating Voltage | Maximum Current | FET On Resistance |
---|---|---|---|---|
DRV8462 | Stepper Driver | 65 V | 10 A | 100 mΩ |
DRV8452 | 48 V | 5 A | 100 mΩ | |
DRV8262 | Brushed-DC Driver | 65 V | 20 A | 50 mΩ |
DRV8252 | 48 V | 10 A | 50 mΩ | |
DRV8243-Q1 | 35 V | 12 A | 85 mΩ | |
DRV8244-Q1 | 35 V | 21 A | 45 mΩ | |
DRV8245-Q1 | 35 V | 32 A | 30 mΩ | |
DRV8962 |
Half-bridge Driver |
65 V | 10 A | 100 mΩ |
DRV8952 | 48 V | 5 A | 100 mΩ |