Designing brushless DC motor driver with MP6540

[Introduction]MPS recently launched an integrated compact gate driver circuit with 6 power MOSFETs, namely the MP6540 series, including MP6540A, MP6540H and MP6540HA. The MP6540 is a three-phase brushless DC (BLDC) motor driver that integrates three half-bridges consisting of six N-channel power MOSFETs.

Traditional motor driver architectures combine a motor driver chip and power MOSFETs. For a three-phase BLDC motor, it requires six external MOSFETs to form three legs to drive each phase winding. However, the traditional architecture requires larger circuit boards, which can no longer adapt to the development trend of increasingly miniaturized circuits.

Below we discuss the advantages offered by the MP6540 and its related devices.

Highly integrated

The MP6540 addresses the shortcomings of traditional motor driver architectures. It operates from supply voltages up to 35V and supports 100% duty cycle operation. The MP6540 features low on-resistance, an integrated bidirectional current-sampling amplifier, and a fault-indicating output. It integrates 6 MOSFETs and their corresponding drivers in a small QFN-26 (5mmx5mm) package.

Its integrated current-sampling circuit can perform bidirectional current measurement in the lower MOSFET of each bridge arm, thus avoiding the size and cost issues caused by external current-sampling circuits. The MP6540 also features over-temperature protection (OTP), under-voltage lockout (UVLO), and over-temperature shutdown. Figure 1 shows the functional block diagram of the MP6540.

Designing brushless DC motor driver with MP6540

Figure 1: MP6540 functional block diagram

Excellent cooling performance

Figure 2 shows the two-layer thermal test PCB for the MP6540. The PCB is 2.5cmx2.5cm in size, the copper thickness is 1oz, and the copper cladding area is 6.25cm2. The board size can be adjusted according to different cooling requirements.

Figure 2: Thermal Test Chip

Under the commonly used 120° square wave drive control conditions, the thermal test results show the excellent thermal performance of the MP6540. As shown in Figure 3, the temperature rise is 8°C at 13V input voltage (VIN) and 1.4A output current (IOUT).

Figure 3: 8°C Temperature Rise (13V VIN, 1.4A IOUT)

As shown in Figure 4, the temperature rise is 41°C at 24V VIN and 4A IOUT. This means that an increase in VIN and IOUT will result in an increase in temperature.

Figure 4: 41°C Temperature Rise (24V VIN, 4A IOUT)

MP6540 series devices

With excellent thermal performance, the MP6540 and its related devices are suitable for a variety of three-phase BLDC driver applications.

The MP6540 and MP6540A can deliver up to 10A peak current or 3A continuous current in 1 second. The MP6540H and MP6540HA can provide 6A peak current or 5A continuous current. Additionally, the MP6540A and MP6540HA include independent upper (HS) and lower (LS) inputs.

Table 1 compares the MP6540 series products. The main differences are the VIN range, IOUT and the input logic signal.

Table 1: MP6540 Series Product Comparison

Fast current sampling

All MP6540 series products provide current sampling function for real-time, accurate current measurement, control and motor protection.

Figure 5 shows the internal current sampling circuit of MP6540H. Its output can be programmed by an external resistor (RTERM) and a reference voltage (VREF). Two equal-value resistors are connected to the ADC power supply and ground, which terminates the output.

Figure 5: MP6540H Internal Current Sensing Circuit

Figure 6 shows the measured waveform of the output of the current measurement circuit (CH3: SOB) as a function of the actual IOUT. It eliminates the cost and space required for external current measurement circuitry, resulting in a smaller, simpler and more cost-effective motor drive solution.

Figure 6: Relationship between current detection output (CH3: SOB) and actual current (CH4: IOUT)

in conclusion

This article reviews the advantages offered by the MP6540 family of devices. The series includes MP6540A, MP6540H and MP6540HA, all of which are highly integrated, highly adaptable, excellent thermal performance and fast current measurement, among other benefits.

Source: Core Source Systems

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