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. January 2009 EVAL6227QR demonstration board Rev 2 1/9 www.st.com Demonstration board description 1 Demonstration board description Table 1. 2/9 AN2759 EVAL6227QR pin connections Name Type Function VS 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 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 Bridge A and bridge B power supply Signal ground terminal 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 3/9 R3 R4 R7 REFB SGND DIAGB DIAGA IN2B REFA R8 R2 ENB IN1B R1 ENA R13 R9 C9 R11 C5 R10 C6 14 13 16 25 28 27 C8 U1 IN 2B IN 1B ENB ENA IN 2A IN 1A C7 2 D1 3 L6227Q VREF A 26 IN2A R14 1 VREF B 15 GND 21 GND 17 VBOOT RCA 30 R5 C3 1 22 VSA SENSEA 24 VCP RCB 11 R6 IN1A C2 C10 SENSEA R20 29 20 VSB SENSEB 4/9 12 7 8 10 18 32 9 19 31 23 2 3 4 5 6 SENSEB L6227Q VFQFPN5x5 NC NC NC NC NC OUT1B OUT2B OUT1A OUT2A NC NC NC NC NC C4 OUT1B OUT2B OUT1A OUT2A PGND VS Figure 3. R21 C1 Demonstration board description AN2759 EVAL6227QR demonstration board schematic R12 AN2759 Demonstration board description Table 3. EVAL6227QR part list Part reference Part value Part description C1 220 nF/25 V Capacitor C2 220 nF/63 V Capacitor C3 10 nF/25 V Capacitor C4 100 µF/63 V Capacitor C5, C6 5.6 nF Capacitor C7, C10 820 pF Capacitor C8, C9 220 nF Capacitor D1 BAT46SW Diode R1, R2, R3, R4, R7, R8, R9, R10 100 kΩ, 5%, 0.25 W Resistor R5, R6 100 kΩ, 1%, 0.25 W Resistor R11, R13 20 kΩ, 5 %, 0.25 W Resistor R12, R14 2 kΩ, 5 %, 0.25 W Resistor R20, R21 0.4 Ω, 1 W Resistor U1 L6227Q Dual full-bridge in VFQFPN5x5 D1, C1 and C3 constitute a charge pump circuit, which generates the supply voltage for the high-side integrated MOSFETs. Due to voltage and current switching at relatively high frequency, these components are connected through short paths in order to minimize induced noise on other circuitries. R1, R2 and C5, C6 are used by the overcurrent protection integrated circuitry (disable time tDISABLE is about 200 µs and delay time tDELAY about 1 µs using the values in Table 3). R5, C7 and R6, C10 are used to set the off-time tOFF of the two PWM channels at about 50 µs. The off-time should be adjusted according to the motor electrical characteristics and supply voltage by changing R5, C7 and R6, C10 values. R11, R12, C8 and R13, R14, C9 are low-pass filters which provide an external reference voltage through a PWM output of a microcontroller. Figure 4, Figure 5 and Figure 6 show the placement of the components and the layout of the two layers of the EVAL6227QR demonstration board. A GND area has been used to improve the IC power dissipation. 5/9 Demonstration board description Figure 4. AN2759 Component placement 27 mm 32 mm Figure 5. 6/9 Top layer layout AN2759 Demonstration board description Figure 6. Bottom layer layout 7/9 Revision history 2 AN2759 Revision history Table 4. 8/9 Document revision history Date Revision Changes 06-Oct-2008 1 Initial release 28-Jan-2009 2 Updated value in Table 2: EVAL6227QR electrical specification (recommended value) on page 3 AN2759 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no liability whatsoever relating to the choice, selection or use of the ST products and services described herein. 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