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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.
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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
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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.
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Demonstration board description
Figure 4.
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Component placement
27 mm
32 mm
Figure 5.
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Top layer layout
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Demonstration board description
Figure 6.
Bottom layer layout
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Revision history
2
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Revision history
Table 4.
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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
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