ST AN2759 APPLICATION NOTE

AN2759

Application note

EVAL6227QR demonstration board using a dual full-bridge L6227Q for motor control applications

Introduction

This application note describes the demonstration board of the DMOS dual full-bridge L6227Q designed for motor control applications. The board implements a typical application that can be used as a reference design to drive two-phase bipolar stepper motors with currents up to 1A DC, multiple DC motors and a wide range of inductive loads.

Thanks to the small footprint of the L6227Q (QFN 5 x 5 mm, 32-lead) the PCB is very compact (27 x 32 mm).

Figure 1. EVAL6227QR demonstration board

January 2009

Rev 2

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Demonstration board description	AN2759

1 Demonstration board description

Table 1.	EVAL6227QR pin connections
Name		Type	Function
VS		Power supply	Bridge A and bridge B power supply
PGND		Ground	Power ground terminal
IN1A		Logic input	Bridge A logic input 1
IN2A		Logic input	Bridge A logic input 2
ENA		Logic input	Bridge A enable (active high). When low, the power DMOSs
			of bridge A are switched OFF.
IN1B		Logic input	Bridge B logic input 1
IN2B		Logic input	Bridge B logic input 2
ENB		Logic input	Bridge B enable (active high). When low, the power DMOSs
			of bridge B are switched OFF.
DIAGA		Open drain output	Bridge A diagnostic pin. When low, an overcurrent or
			overtemperature event of bridge A is signaled.
DIAGB		Open drain output	Bridge B diagnostic pin. When low, an overcurrent or
			overtemperature event of bridge B is signaled.
SGND		Ground	Signal ground terminal
REFA		Analog input	Bridge A current controller reference voltage
REFB		Analog input	Bridge B current controller reference voltage
OUT1A		Power output	Bridge A output 1
OUT2A		Power output	Bridge A output 2
OUT1B		Power output	Bridge B output 1
OUT2B		Power output	Bridge B output 2

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AN2759		Demonstration board description
	Figure 2.	EVAL6227QR demonstration board description
		SGND
	IN1B	IN2A
	IN2B	REFA
	REFB	IN1A
	DIAGB	DIAGA

ENB

ENA

PGND

VS

OUT1B

OUT2B

OUT2A

OUT1A

The INx input pins drive the corresponding half-bridge. When low logic level is applied, the low side MOS is switched on, whereas a high logic level turns on the high side MOS.

To perform the PWM current control an analog reference voltage should be provided to each channel of the driver. A fixed reference voltage can be easily obtained through a resistive divider from an external voltage rail and GND (can be the one supplying the microcontroller or the rest of the application).

Otherwise a very simple way to obtain a variable voltage without using a DAC is to low-pass filter a PWM output of a microcontroller.

Table 2 summarizes the electrical specification of the application and Figure 3 shows the electrical schematic.

Table 2.	EVAL6227QR electrical specification (recommended value)
	Parameter	Value
	Supply voltage range (VS)	8 to 52 Vdc
RMS output current rating (OUTx)		up to 1.4 A
	Switching frequency	up to 100 kHz
	Input and enable voltage range	0 to + 5 V
Voltage reference range (REFA, REFB)		0 to + 5 V
	Operating temperature range	-25 to +125°C
L6227Q thermal resistance junction to ambient		42°C/W

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