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 1/9
www.st.com
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
IN1B Logic input Bridge B logic input 1
IN2B Logic input Bridge B logic input 2
Bridge A enable (active high). When low, the power DMOSs
of bridge A are switched OFF.
ENB Logic input
DIAGA Open drain output
DIAGB Open drain output
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
Bridge B enable (active high). When low, the power DMOSs
of bridge B are switched OFF.
Bridge A diagnostic pin. When low, an overcurrent or
overtemperature event of bridge A is signaled.
Bridge B diagnostic pin. When low, an overcurrent or
overtemperature event of bridge B is signaled.
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AN2759 Demonstration board description
Figure 2. EVAL6227QR demonstration board description
SGND
IN1B
IN2B
REFB
DIAGB
IN2A
REFA
IN1A
DIAGA
ENB
ENA
PGND
VS
OUT1B
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.
OUT2B
OUT2A
OUT1A
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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Demonstration board description AN2759
A
Figure 3. EVAL6227QR demonstration board schematic
VS
PGND
C4C4
6
2
4
3
NC
NC5NC
NC
NC
VSB
20
VSA
1
C1C1
3
D1D1
2
C2C2
22
C3C3
VCP
24
VBOOT
17
GND
21
GND
1
OUT2B
OUT1AOUT2
OUT1B
7
8
9
19
31
23
NC
OUT1B
OUT2B
OUT1A
OUT2A
L6227Q
10
18
NC
NC
32
NC
NC
L6227Q VFQFPN5x5
L6227Q VFQFPN5x5
SENSEB
12
SENSEA
29
RCB
11
RCA
30
VREF B
15
VREF A
26
SENSEA SENSEB
R21R21
R20R20
C10C10
R6R6
R5R5
C7C7
IN 1A
27
IN1A
IN 2A
28
IN2A
25
ENA
R1R1
ENA
16
ENB
R2R2
ENB
IN 1B
13
IN1B
IN 2B
14
IN2B
DIAGA
U1
U1
DIAGB
R10R10
R9R9
R8R8R7R7
R4R4
R3R3
C8C8
C6C6
R12R12
C5C5
SGND
R11R11
C9C9
R14R14
R13R13
REFA
REFB
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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
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
100 kΩ, 5%, 0.25 W Resistor
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
t
DISABLE
R5, C7 and R6, C10 are used to set the off-time t
is about 200 µs and delay time t
about 1 µs using the values in Table 3).
DELAY
of the two PWM channels at about 50
OFF
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.
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Demonstration board description AN2759
Figure 4. Component placement
27 mm
32 mm
Figure 5. Top layer layout
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AN2759 Demonstration board description
Figure 6. Bottom layer layout
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Revision history AN2759
2 Revision history
Table 4. Document revision history
Date Revision Changes
06-Oct-2008 1
28-Jan-2009 2
Initial release
Updated value in Table 2: EVAL6227QR electrical specification
(recommended value) on page 3
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AN2759
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