ST AN3134 Application note

AN3134

Application note

EVAL6229QR demonstration board using the L6229Q DMOS driver for a three-phase BLDC motor control application

Introduction

This application note describes the EVAL6229QR demonstration board for the L6229Q DMOS fully integrated three-phase brushless DC motor driver. The board implements a typical application that can be used as a demonstration platform for driving three-phase brushless DC motors with currents up to 1 A DC.

Thanks to the small footprint of the L6229Q (QFN 5x5 mm), the board is a very compact 30x32 mm.

Figure 1. EVAL6229QR demonstration board

April 2010

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Demonstration board description	AN3134

1 Demonstration board description

	Table 1.	EVAL6229QR pin description
	Name	Type	Function
	VS	Power supply	Hal bridges power supply voltage
	PGND	Ground	Power ground terminal.
	VDD	Power supply	Hall effect sensors pull-up voltage.
	H1	Sensor input	Single ended hall effect sensor input 1.
	H2	Sensor input	Single ended hall effect sensor input 2.
	H3	Sensor input	Single ended hall effect sensor input 3.
	SGND	Ground	Signal ground terminal.
	DIAG	Open-drain output	Diagnostic pin. When ‘low’, signals an overcurrent or
			overtemperature event.
	TACHO	Open-drain output	Frequency-to-voltage open drain output. Every pulse from H1 pin is
			shaped as a fixed and adjustable length pulse.
	F/R	Logic input	Selects the direction of the rotation (‘H’ = CW; ‘L’ = CCW).
	EN	Logic input/output	Chip enable (active ‘high’). When ‘low’, switches OFF all power
			MOSFETs of three half-bridges.
	VREF	Analog input	Current controller reference voltage.
	BRAKE	Logic input	Brake input pin. When ‘low, switches ON all high-side power
			MOSFETs implementing the brake function.
	OUT1	Power output	Output phase 1.
	OUT2	Power output	Output phase 2.
	OUT3	Power output	Output phase 3.

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AN3134	Demonstration board description

Figure 2. EVAL6229QR demonstration board pin locations

The decoding logic integrated in the device is a combinatory logic which provides the appropriate driving signals for the three-phase bridge outputs, based on the signals coming from the three hall sensors H1, H2 and H3. The hall sensors detect rotor position in a 3- phase BLDC motor.

The EN pin connected to the diagnostic output DIAG is used to implement the overcurrent and thermal protection.

To perform PWM current control, an analog reference voltage should be provided at the VREF pin. A fixed reference voltage can be easily obtained through a resistor divider from an external voltage rail and GND (possibly that which supplies the microcontroller or the rest of the application). Alternatively, a very simple way of obtaining a variable voltage without using a DAC is to low-pass filter the PWM output of a microcontroller.

Table 2 summarizes the electrical specifications of the application, Figure 3 shows the electrical schematic, and Table 3 provides the component list.

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