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.
Name
VS
PGND
IN1A
IN2A
ENA
IN1B
IN2B
ENB
DIAGA
DIAGB
SGND
REFA
REFB
OUT1A
OUT2A
OUT1B
OUT2B
EVAL6227QR pin connections
Type
Power supply
Ground
Logic input
Logic input
Logic input
Logic input
Logic input
Logic input
Open drain output
Open drain output
Ground
Analog input
Analog input
Power output
Power output
Power output
Power output
Function
Bridge A and bridge B power supply
Power ground terminal
Bridge A logic input 1
Bridge A logic input 2
Bridge A enable (active high). When low, the power DMOSs
of bridge A are switched OFF.
Bridge B logic input 1
Bridge B logic input 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.
Signal ground terminal
Bridge A current controller reference voltage
Bridge B current controller reference voltage
Bridge A output 1
Bridge A output 2
Bridge B output 1
Bridge B output 2
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AN2759
Figure 2.
Demonstration board description
EVAL6227QR demonstration board description
SGND
IN1B
IN2B
REFB
DIAGB
ENB
IN2A
REFA
IN1A
DIAGA
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
Supply voltage range (VS)
RMS output current rating (OUTx)
Switching frequency
Input and enable voltage range
Voltage reference range (REFA, REFB)
Operating temperature range
L6227Q thermal resistance junction to ambient
Value
8 to 52 Vdc
up to 1.4 A
up to 100 kHz
0 to + 5 V
0 to + 5 V
-25 to +125°C
42°C/W
3/9
3
1
21
17
24
22
VSA
GND
GND
VCP
VSB
20
IN 1A
IN 2A
ENA
ENB
IN 1B
VREF A
VREF B
VBOOT
RCA
RCB
SENSEA
SENSEB
26
15
30
11
29
12
R5
R5
C7
R6
R20
R20
R21
R12
R14
4/9
C1
Figure 3.
VS
C2
D1
C4
C3
2
1
Demonstration board description
PGND
IN1A
27
28
R1
R2
IN2A
NC
NC
NC
NC
NC
2
3
4
5
6
ENA
25
16
13
14
IN 2B
ENB
L6227Q
OUT1A
OUT2A
OUT1B
OUT2B
31
23
9
19
OUT1A
OUT2A
OUT1B
OUT2B
IN1B
IN2B
DIAGA
NC
NC
NC
NC
NC
7
8
10
18
32
L6227Q VFQFPN5x5
DIAGB
R3
R4
C6
C5
R7
R8
R9
R10
U1
SENSEA
C10
SENSEB
EVAL6227QR demonstration board schematic
SGND
R11
REFA
C8
R13
REFB
AN2759
C9
AN2759
Demonstration board description
Table 3.
EVAL6227QR part list
Part value
220 nF/25 V
220 nF/63 V
10 nF/25 V
100
µF/63
V
5.6 nF
820 pF
220 nF
BAT46SW
100 kΩ, 5%, 0.25 W
100 kΩ, 1%, 0.25 W
20 kΩ, 5 %, 0.25 W
2 kΩ, 5 %, 0.25 W
0.4
Ω,
1 W
L6227Q
Part description
Capacitor
Capacitor
Capacitor
Capacitor
Capacitor
Capacitor
Capacitor
Diode
Resistor
Resistor
Resistor
Resistor
Resistor
Dual full-bridge in VFQFPN5x5
Part reference
C1
C2
C3
C4
C5, C6
C7, C10
C8, C9
D1
R1, R2, R3, R4, R7,
R8, R9, R10
R5, R6
R11, R13
R12, R14
R20, R21
U1
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
is about 200
µs
and delay time t
DELAY
about 1
µs
using the values in
Table 3).
R5, C7 and R6, C10 are used to set the off-time t
OFF
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
微控制器 MCU
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