ST STEVAL-IHM031V1 User manual

October 2010 Doc ID 17701 Rev 1 1/45
UM0971
User manual
STEVAL-IHM031V1 low voltage
three-phase inverter demonstration board
Introduction
The STEVAL-IHM031V1 demonstration board is a low voltage three-phase power stage
inverter designed to perform permanent magnet motor controls. To this purpose, it must be
connected to an additional control logic stage (usually based on an 8/32-bit microcontroller).
According to the existing wide range of motor types and control techniques, it has been
designed to offer large flexibility by allowing full configurability.
In particular, it can be used for implementing scalar control (also known as current six-step
mode or trapezoidal shaped back-EMF) and field oriented control (sinusoidal-shaped back-
EMF PMSM).
The system has been specifically designed to achieve accurate and fast conditioning of the
current and back-EMF feedbacks, thereby matching the requirements typical of high-end
applications such as field oriented motor control. Back-EMF conditioning networks can
include an amplification stage for managing very low motor speed. Circuit networks are
provided to implement different techniques of sensorless speed and rotor position detection.
The input voltage range is from 12 V up to 24 V with no need to set any jumper for selecting
the input voltage level. Nominal power is up to 120 W. A dedicated power supply has been
designed to provide power +5 V and +3.3 V voltages to supply the control stage board. The
latter can be connected to the STEVAL-IHM031V1 board by using a dedicated motor control
connector, generally available in most boards based on microcontrollers produced by ST.
The three-phase inverter bridge is based on the STS8DNH3LL power MOSFET dual-in-
package SO-8 and L6387E gate driver. The board is self-protected by overcurrent events
and for each power MOSFET the case temperature is sensed through a temperature
sensor. A connector exists to read signals coming from encoder and Hall sensors.
Figure 1. STEVAL-IHM031V1 demonstration board
www.st.com

Contents UM0971
2/45 Doc ID 17701 Rev 1
Contents
1 STEVAL-IHM031V1 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1 Electrical and functional characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2 Target application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3 Safety and operating instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.2 Demonstration board intended use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.3 Demonstration board installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.4 Electronic connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.5 Demonstration board operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Board description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 System architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Power supply circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.1 LD1117xx33 and LD1117xx50 characteristics . . . . . . . . . . . . . . . . . . . . 9
2.2.2 L4976 characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.3 Inverse polarity protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3 Gate driving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.4 Three-phase inverter power switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.4.1 STS8DNH3LL characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5 BEMF conditioning network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.5.1 Zero-crossing methods for BEMF reading . . . . . . . . . . . . . . . . . . . . . . . 16
2.5.2 Low amplitude BEMF signal amplification . . . . . . . . . . . . . . . . . . . . . . . 16
2.5.3 Virtual neutral (or natural) point reconstruction . . . . . . . . . . . . . . . . . . . 17
2.6 Current sensing and conditioning network . . . . . . . . . . . . . . . . . . . . . . . . 18
2.6.1 Bipolar current reading configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.6.2 Unipolar current reading configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.6.3 Three-shunt current reading configuration . . . . . . . . . . . . . . . . . . . . . . . 21
2.6.4 Single-shunt current reading configuration . . . . . . . . . . . . . . . . . . . . . . 21
2.6.5 Overcurrent protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.7 Temperature sensing and protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3 Descriptions of connectors and jumpers . . . . . . . . . . . . . . . . . . . . . . . 24
3.1 Jumper description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

UM0971 Contents
Doc ID 17701 Rev 1 3/45
3.2 Connector placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3 Connector description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4 STEVAL-IHM0031V1 hardware settings . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.1 Settings for six-step current control (block commutation) . . . . . . . . . . . . . 27
4.2 Settings for three-shunt configuration and FOC control . . . . . . . . . . . . . . 28
5 Board schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6 BOM list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

List of tables UM0971
4/45 Doc ID 17701 Rev 1
List of tables
Table 1. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 2. Electrical characteristics of the LD1117#33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 3. Electrical characteristics of the LD1117#50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table 4. Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 5. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 6. Low amplitude BEMF jumper configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 7. Virtual neutral point reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 8. AC current jumper configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 9. DC current jumper configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 10. Three-shunt jumper settings (default) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 11. Single-shunt jumper settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 12. Jumper description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Table 13. Connector pinout description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Table 14. Single-shunt current reading - jumper configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Table 15. Sensored mode - jumper configuration (Hall sensors for rotor position detecting) . . . . . . . 27
Table 16. Sensorless mode - jumper configuration (BEMF reading w/o amplification) . . . . . . . . . . . 27
Table 17. Sensorless mode - jumper configuration (low BEMF reading w/o amplification) . . . . . . . . 28
Table 18. Virtual neutral point reconstruction - jumper configuration . . . . . . . . . . . . . . . . . . . . . . . . . 28
Table 19. Three-shunt current reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Table 20. Encoder/Hall sensor speed reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Table 21. BOM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Table 22. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

UM0971 List of figures
Doc ID 17701 Rev 1 5/45
List of figures
Figure 1. STEVAL-IHM031V1 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 2. STEVAL-IHM031V1 block scheme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 3. Power supply block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 4. LD1117 family packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 5. Typical application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 6. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 7. Gate driving network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 8. STS8DNH3LL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 9. Back-EMF conditioning network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 10. Low back-EMF amplification network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 11. AC current reading configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 12. Single-shunt configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 13. Overcurrent protection circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 14. Temperature sensing circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Figure 15. STEVAL-IHM0031V1 connector placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 16. Bemf_hall_encoder schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 17. Current conditioning network schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 18. Driver and power MOSFET schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Figure 19. Motor control connector schematic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 20. Power supply schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

STEVAL-IHM031V1 features UM0971
6/45 Doc ID 17701 Rev 1
1 STEVAL-IHM031V1 features
1.1 Electrical and functional characteristics
The information below lists the converter specification data and the main parameters fixed
for the STEVAL-IHM0031V1 demonstration board.
●Minimum input voltage: 12 VDC
●Maximum input voltage: 24 VDC
●Maximum output power for motor up to 120 W
●Circuit protection against input reverse polarity
●5 VDC auxiliary power supply based on the LD1117xx50
●3.3 VDC auxiliary power supply based on the LD1117xx33
●8 VDC auxiliary power supply based on the L4976
●Power MOSFET STS8DNH3LL dual N-channel in SO-8 package
●Motor control connector for interface with STM32 and STM8 microcontroller family
demonstration boards
●Hall/encoder inputs
●Fully configurable to implement both scalar and field oriented motor control driving
strategies
1.2 Target application
●Battery powered high-end tools
●Medical applications
●Autonomous mover
●Super silent and high-efficiency water pump for cooling/heating applications
1.3 Safety and operating instructions
1.3.1 General
Warning: During assembly and operation, the STEVAL-IHM031V1
demonstration board poses several inherent hazards,
including bare wires, moving or rotating parts, and hot
surfaces. There is a danger of serious personal injury and
damage to property, if the kit or its components are
improperly used or installed incorrectly.
All operations involving transportation, installation and use, as well as maintenance, is to be
carried out by skilled technical personnel (national accident prevention rules must be
observed). For the purposes of these basic safety instructions, “skilled technical personnel”
are suitably qualified people who are familiar with the installation, use, and maintenance of
power electronic systems.

UM0971 STEVAL-IHM031V1 features
Doc ID 17701 Rev 1 7/45
1.3.2 Demonstration board intended use
The STEVAL-IHM031V1 demonstration board is a component designed for demonstration
purposes only, and is not to be used for electrical installation or machinery. The technical
data as well as information concerning the power supply conditions must be taken from the
relevant documentation and strictly observed.
1.3.3 Demonstration board installation
The installation and cooling of the demonstration board is in accordance with the
specifications and the targeted application.
●The motor drive converters are protected against excessive strain. In particular, no
components are to be bent, or isolating distances altered, during the course of
transportation or handling.
●No contact must be made with other electronic components and contacts.
●The boards contain electrostatically sensitive components that are prone to damage
through improper use. Electrical components must not be mechanically damaged or
destroyed (to avoid potential health risks).
1.3.4 Electronic connections
Applicable national accident prevention rules must be followed when working on the main
power supply with a motor drive. The electrical installation is completed in accordance with
the appropriate requirements (e.g., cross-sectional areas of conductors, fusing, PE
connections, etc.).
1.3.5 Demonstration board operation
A system architecture which supplies power to the STEVAL-IHM031V1 demonstration board
is equipped with additional control and protective devices in accordance with the applicable
safety requirements (e.g., compliance with technical equipment and accident prevention
rules).
Warning: Do not touch the demonstration board after disconnection
from the voltage supply, as several parts and power terminals
which contain possibly energized capacitors need to be
allowed to discharge.

Board description UM0971
8/45 Doc ID 17701 Rev 1
2 Board description
2.1 System architecture
The system can be schematized in five main blocks (see Figure 2):
●Power supply: this section accepts a supply voltage between 12 V and 24 V and
provides, in output, three supply voltage levels: +3.3 V, +5 V, and +8 V. The first two are
also available on the MC connector for supplying the control unit (not part of this
STEVAL-IHM031V1 board). Please read Section 2.2 for details on used devices.
●Gate driving: the power switches of the three-phase inverter bridge are driven by (3x)
L6387E high/low side drivers. Refer to Section 2.3 for details on driving network.
●Three-phase inverter: the power MOSFET STS8NH3LL is the device used for the
inverter bridge. As it is made up of two NMOS integrated in the same package, three
ICs are used in total. Please consult Section 2.4 for details on power switches.
●Back-EMF voltage conditioning: this circuit senses and/or amplifies the voltage back-
EMF of each motor phase. See Section 2.5 for details.
●Current reading and conditioning: this circuit network is used to sense and amplify the
current flowing through the shunt resistors. This block implements a hardware
overcurrent protection. See Section 2.6 for details on how it operates.
●Motor speed and rotor position: a connector and circuitry when connecting a
quadrature encoder/Hall sensor signal for motor speed/rotor position sensing.
●Control unit Interface: this is a signal interface (motor control connector) where a
control unit board can be connected to implement motor driving. ST distributes several
demonstrators and demonstration boards which are compatible with this interface. For
references, please read Section 6.
Figure 2. STEVAL-IHM031V1 block scheme
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DRIVING
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ANDCONDITIONING
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/VERCURRENT
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3PEED0OSITION
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O
W
E
R
S
U
P
P
L
Y
0-3-
-OTOR
PH INVERTER
6
 6
6
$#BUS
 6

UM0971 Board description
Doc ID 17701 Rev 1 9/45
2.2 Power supply circuit
The STEVAL-IHM031V1 board is designed to work with an input voltage bus ranging from
12 V up to 24 V (nominal values). The bus voltage supplies the three-phase inverter stage.
To allow proper working below the nominal 12 V lower voltage limit, an opportune power
supply stage has been designed, taking into account several aspects, such as:
●ensuring supply voltage for the gate driver L6387E (+8 V)
●+5 VDC generation with current capability of 800 mA
●+3.3 VDC generation with current capability of 800 mA
●providing externally auxiliary 8 VDC power supply
Figure 3 is a block diagram representation of the power supply stage used for the
STEVAL-IHM031V1 board:
Figure 3. Power supply block diagram
In a case where the bus voltage input is below nominal voltage (12 VDC), the L4976
regulator is no longer able to provide 8 V voltage level at its output. Nevertheless, it is still
possible to continue using the board by providing an external +8 V voltage through
connector J21.
2.2.1 LD1117xx33 and LD1117xx50 characteristics
The LD1117xx33/50 is a low drop voltage regulator able to provide up to 800 mA of output
current at 3.3 V/5 V output voltage. The main features follow.
!-V
, ,$3
,$3
6$# 6$#
6$#
)NVERSE
POLARITY
PROTECTION
6
$#

Board description UM0971
10/45 Doc ID 17701 Rev 1
Figure 4. LD1117 family packages
DPAK
SO-8
TO-220
SOT-223
1231
3
12
2
3
Table 1. Absolute maximum ratings
Symbol Parameter Value Unit
VIN (1) DC input voltage 15 V
PTOT Power dissipation 12 W
TSTG Storage temperature range -40 to +150 °C
TOP Operating junction temperature range for C version -40 to +125 °C
for standard version 0 to +125 °C
1. Absolute maximum rating of VIN = 18 V, when IOUT is lower than 20 mA.
Table 2. Electrical characteristics of the LD1117#33
Symbol Parameter Test condition Min. Typ. Max. Unit
VOOutput voltage Vin = 5.3 V, IO= 10 mA, TJ= 25 °C 3.267 3.3 3.333 V
VOOutput voltage IO= 0 to 800 mA, Vin = 4.75 to 10 V 3.235 3.365 V
ΔVOLine regulation Vin = 4.75 to 15 V, IO= 0 mA 1 6 mV
ΔVOLoad regulation Vin = 4.75 V, IO= 0 to 800 mA 1 10 mV
ΔVOTemperature stability 0.5 %
ΔVOLong term stability 1000 hrs, TJ= 125 °C 0.3 %
Vin Operating input voltage IO= 100 mA 15 V
IdQuiescent current Vin ≤15 V 5 10 mA
IOOutput current Vin = 8.3 V, TJ= 25 °C 800 950 1300 mA
eN Output noise voltage B = 10 Hz to 10 kHz, TJ= 25 °C 100 µV
SVR Supply voltage rejection IO= 40 mA, f = 120 Hz, TJ= 25 °C
Vin = 6.3 V, Vripple = 1 VPP
60 75 dB

UM0971 Board description
Doc ID 17701 Rev 1 11/45
VdDropout voltage
IO= 100 mA 1 1.1
VIO= 500 mA 1.05 1.15
IO= 800 mA 1.10 1.2
Thermal regulation Ta= 25 °C, 30 ms pulse 0.01 0.1 %/W
Table 2. Electrical characteristics of the LD1117#33 (continued)
Symbol Parameter Test condition Min. Typ. Max. Unit
Table 3. Electrical characteristics of the LD1117#50
Symbol Parameter Test condition Min. Typ. Max. Unit
VOOutput voltage Vin = 7 V, IO= 10 mA, TJ= 25 °C 4.95 5 5.05 V
VOOutput voltage IO= 0 to 800 mA, Vin = 6.5 to 15 V 4.9 5.1 V
ΔVOLine regulation Vin = 6.5 to 15 V, IO= 0 mA 1 10 mV
ΔVOLoad regulation Vin = 6.5 V, IO= 0 to 800 mA 1 15 mV
ΔVOTemperature stability 0.5 %
ΔVOLong term stability 1000 hrs, TJ= 125 °C 0.3 %
Vin Operating input voltage IO= 100 mA 15 V
IdQuiescent current Vin ≤15 V 5 10 mA
IOOutput current Vin = 10 V, TJ= 25 °C 800 950 1300 mA
eN Output noise voltage B = 10 Hz to 10 kHz, TJ= 25 °C 100 µV
SVR Supply voltage rejection IO= 40 mA, f = 120 Hz, TJ= 25 °C
Vin = 8 V, Vripple = 1 VPP
60 75 dB
VdDropout voltage
IO= 100 mA 1 1.1
VIO= 500 mA 1.05 1.15
IO= 800 mA 1.10 1.2
Thermal regulation Ta= 25 °C, 30 ms pulse 0.01 0.1 %/W

Board description UM0971
12/45 Doc ID 17701 Rev 1
2.2.2 L4976 characteristics
The L4976 is a step down monolithic power switching regulator delivering 1 A at a voltage
between 3.3 V and 50 V (selected by a simple external divider). A wide input voltage range
from 8 V to 55 V and output voltages regulated from 3.3 V to 40 V cover the majority of
today's applications. Features of this new generation of DC-DC converters include pulse-by-
pulse current limit, hiccup mode for short-circuit protection, voltage feedforward regulation,
protection against feedback loop disconnection and thermal shutdown. The device is
available in plastic dual-in-line, MINIDIP 8 for standard assembly, and SO16W for SMD
assembly. It features:
●Up to 1 A step down converter
●Operating input voltage from 8 V to 55 V
●Precise 5.1 V reference voltage
●Output voltage adjustable from 0.5 V to 50 V
●Switching frequency adjustable up to 300 kHz
●Voltage feedforward
●Zero load current operation
●Internal current limiting (pulse-by-pulse and hiccup mode)
●Protection against feedback disconnection
●Thermal shutdown
Figure 5. Typical application circuit
2.2.3 Inverse polarity protection
To prevent accidental polarity inversion when supplying the STEVAL-IHM031V1 board
through connector J22, a protection circuit has been provided. It is made up of a diode and
a fuse of 6.3 A. In the case of polarity inversion occurring, the fuse F1 is permanently
damaged and needs to be replaced before the next system operation.
2.3 Gate driving
The L6387E is a high-voltage device, in the DIP-8 and SO-8 package, manufactured with
BCD “OFF-LINE” technology. It has a driver structure that enables the driving of an
independent referenced N-channel power MOSFET or IGBT. The high side (floating) section
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UM0971 Board description
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is enabled to work with voltage rail up to 600 V. The logic inputs are CMOS/TTL compatible
for ease of interfacing with controlling devices. It features:
●High voltage rail up to 600 V
●dV/dt immunity ±50 V/nsec in full temperature range
●Driver current capability:
– 400 mA source
– 650 mA sink
●Switching times 50/30 nsec rise/fall with 1 nF load
●CMOS/TTL Schmitt trigger inputs with hysteresis and pull down
●Internal bootstrap diode
●Outputs in phase with inputs
●Interlocking function
Figure 6. Block diagram
Figure 7 shows, in more detail, the circuit utilized for the turn-on and turn-off of the power
MOSFETs.
Figure 7. Gate driving network
As can be deduced from Figure 7, during turn-on, power MOSFET gate capacitances are
charged through R1 and R4 (220 Ω) resistors, while turn-off is fastened by the presence of
diode D1 and D2.
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Board description UM0971
14/45 Doc ID 17701 Rev 1
The driver L6387E offers an interlocking feature to avoid undesired simultaneous turn-on of
both driven power switches.
2.4 Three-phase inverter power switches
2.4.1 STS8DNH3LL characteristics
The STS8DNH3LL is a dual N-channel (30 V - 0.018 Ω- 8 A) low gate charge STripFET™ III
power MOSFET in the SO-8 package.
Figure 8. STS8DNH3LL
Table 4. Features
Type VDSS RDS(on) max ID
STS8DNH3LL 30 V < 0.022 Ω8 A
Table 5. Absolute maximum ratings
Symbol Parameter Value Unit
VDS Drain source voltage (vGS = 0) 30 V
VGS Gate source voltage ±16 V
IDDrain current (continuous) at TC= 25 °C 8 A
IDDrain current (continuous) at TC= 100 °C 5 A
IDM (1)
1. Pulse width limited by safe operating area
Drain current (pulsed) 32 A
PTOT Total dissipation at TC= 25 °C 2 W
EAS(2)
2. Starting TJ= 25 °C, ID= 6 A
Single-pulse avalanche energy 100 mJ
SO-8

UM0971 Board description
Doc ID 17701 Rev 1 15/45
2.5 BEMF conditioning network
Permanent magnet brushless DC motors require the electronic commutation of motor
phases to respect the synchronization between statoric flux and that of the permanent
magnet of the rotor.
Generally, a BLDC motor drive uses one or more sensors giving positional information to
maintain synchronization.
Such implementation results in a higher drive cost due to sensor wiring and implementation
in the motor. Moreover, sensors cannot be used in applications where the rotor is in closed
housing and the number of electrical entries must be kept to a minimum value.
Therefore, for cost and technical reasons, the BLDC sensorless drive is an essential
capability of a brushless motor controller. There exists various implementations of
sensorless BLDC control techniques, most of them using motor back-EMF voltage as rotor
position sensing signal.
In ST technical papers and application notes (please refer to Section 6) some topologies,
their advantages and drawbacks, as well as their practical implementation, are described in
detail.
STEVAL-IHM031V1 allows the easy implementation of most topologies described.
The network for reading back-EMF phase voltage has been designed to offer maximum
configurability according to different motor type operations and control strategy.
For each motor phase, there exists a conditioning network such as the one schematized
below in Figure 9:
Figure 9. Back-EMF conditioning network
The switch can assume one of two different positions according to the type of back-EMF
sensing methodology used.
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Board description UM0971
16/45 Doc ID 17701 Rev 1
2.5.1 Zero-crossing methods for BEMF reading
Putting the switch on Pos 1, the motor phase voltage is directly input to the voltage divider
block.
When the patented ST zero-crossing method is used, the voltage divider is simply made up
of a 10 kΩseries resistor for limiting the current to the control unit that processes the signal.
When the “classic” (industry standard) method is used, the voltage divider must scale and
filter the back-EMF voltage before it is input to the control unit. The partition ratio
determination depends on motor bus voltage. Therefore, the voltage divider resistor and
filtering capacitor values are calculated by the user.
2.5.2 Low amplitude BEMF signal amplification
When the back-EMF signal is very low (low speed) or for low voltage applications, the back-
EMF zero-crossing detection can become difficult due to the very weak signal. The
application note AN1103; improved B-EMF detection for low-speed and low-voltage
applications with ST72141, offers a circuit solution for improving back-EMF zero-crossing
detection at very low speeds or for low voltage applications.
This circuit can greatly improve the performance of sensorless BLDC drives in low voltage
applications, especially for automotive applications. With this technique, the sensorless
drive can be used in much wider speed ranges.
With reference to Figure 9, by setting Pos 2, an amplification block is inserted in back-EMF
signal processing, therefore allowing all the cases listed above to be covered.
For the actual amplification network, please see the circuit schematic in Figure 10:
Figure 10. Low back-EMF amplification network
The output voltage Vout can be expressed in function of generic back-EMF phase voltage
Vbemf_x in this way:
Equation 1
With the resistor values actually used in the circuit schematic:
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UM0971 Board description
Doc ID 17701 Rev 1 17/45
Equation 2
●R2=1500 Ω
●R=10000 Ω
we have:
Equation 3
and:
Equation 4
If needed, further adjustments on amplified Vout voltage can be done by means of the next
block voltage divider, as shown in Figure 1 and 9.
Table 6 lists the involved jumpers and their positions for low amplitude BEMF amplification:
Moreover, please refer to Section 3 for jumper setting configurations for outputting Vout
signals through the Motor Control connector.
2.5.3 Virtual neutral (or natural) point reconstruction
When the classic analog method is used for back-EMF reading, there is a need to
reconstruct the virtual neutral point of motor windings (when star connected). To this aim,
there are different schemes. In particular, STEVAL-IHM031V1 allows implementation of
both the following (though not at the same time):
1. to rebuild the virtual neutral motor using three resistors and a voltage divider and filter
2. a voltage divider of DC bus voltage to get a proper reference voltage which follows DC
bus fluctuation
For a detailed explanation and principle schemes, please see Section 3 of application note
AN1946; Sensorless BLDC motor control and BEMF sampling methods with ST7MC.
Table 7 lists the involved jumpers and their positions for selecting how to reconstruct the
virtual neutral point:
Table 6. Low amplitude BEMF jumper configuration
Jumper Position
J1 Between 1-2
J4 Between 1-2
J7 Between 1-2
R1 R3 R4 r 2200Ω====
Vbias 2.5 R1 R+
R1 R2+
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GR1 R+
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Board description UM0971
18/45 Doc ID 17701 Rev 1
2.6 Current sensing and conditioning network
2.6.1 Bipolar current reading configuration
The details of bipolar current sensing (also referred to as Alternating AC) reading
configuration is shown in Figure 11. In this configuration, the alternating current signal on
the shunt resistor, with positive and negative values, must be translated to be compatible
with the single positive input of the microcontroller ADC converter used to read the current
value. This means that the op amp must be biased in order to obtain a voltage on the output
which makes it possible to measure the symmetrical alternating input signal.
Basically, the output signal from the op amp is made up of two terms: a bias voltage Vbias
and an amplification of voltage drop across the shunt resistor (G). The formulas below show
the relationships between network components and signal values.
Figure 11. AC current reading configuration
Equation 5
Where:
Equation 6
and:
Table 7. Virtual neutral point reconstruction
Jumper Position Description
J9 Between 1-2 Three resistors used
Between 2-3 DC bus voltage divider
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Vout Vbias G Rshunt I⋅()⋅+=
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R3
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⋅=

UM0971 Board description
Doc ID 17701 Rev 1 19/45
Equation 7
With the resistor values actually used in the circuit schematic, it is:
●R1=5100 Ω
●R2=920 Ω
●R3=470 Ω
●r= 1000 Ω
●R= 5100 Ω
Therefore getting:
●Vbias=1.7534 Ω
and:
●G=1.944
This means that the maximum instantaneous current amplifiable without distortion is 8 A
(corresponding to Vout = 3.3 V). The user can modify the maximum current value by
changing the shunt resistor values.
Table 8 lists the involved jumper and their positions for AC current reading configuration:
Note: The resistor R2 value of 920 Ωin the circuit schematic is made up of the sum of two
resistors: one of 100 Ω, belonging to the low-pass filter across the shunt resistor and the
second of 820 Ωbelonging to the amplifier network.
2.6.2 Unipolar current reading configuration
The details of the single-shunt current sensing (also referred to as direct DC current)
configuration are shown in Figure 12. This configuration is used when sampling is done on
positive current on the shunt resistor. The only positive value read on the shunt resistor
allows the setting of a higher gain for the op amp than the one set in AC reading mode.
Table 8. AC current jumper configuration
Jumper Position
J10 Present
J11 Between 1-2
J12 Present
G1
1
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R2
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R3
--------++
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Board description UM0971
20/45 Doc ID 17701 Rev 1
Figure 12. Single-shunt configuration
It is possible to calculate the voltage on the output of the op amp Vout as the sum of a bias
voltage, Vbias, and an amplification of voltage drop across the shunt resistor (G):
Equation 8
Where:
Equation 9
and:
Equation 10
With the resistor values actually used in the circuit schematic, we have:
●R1= 1100 Ω
●R2=1000 Ω
●R3=18 Ω
●R4=2700
●r=1000 Ω
●R=11900 Ω
Therefore getting:
●Vbias=0.2219 V
●G=6.2
Table 9 lists the involved jumpers and their positions for DC current reading configuration:
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