ST EVALSTPM34 User manual

September 2015
DocID026226 Rev 2
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www.st.com
UM1748
User manual
EVALSTPM34, EVALSTPM33, EVALSTPM32 evaluation board
Introduction
This user manual describes the EVALSTPM34, EVALSTPM33, EVALSTPM32 evaluation board.
The STPM3x is an ASSP family of mixed signals designed for high accuracy measurement of power
and energy in power line systems using the Rogowski coil, current transformer or shunt current sensors.
According to p/n, the device has up to two voltages and two current channels, for energy measurement
in dual-phase and single-phase (with or without neutral current monitoring) electricity metering systems.
The STPM3x devices provide instantaneous voltage and current waveforms and calculate voltage and
current RMS values, active, reactive and apparent powers and energies for each channel. Moreover,
they embed a full set of calibration and compensation parameters which allow the meter to fit tight
accuracy standards (EN 50470-x, IEC 62053-2x, ANSI12.2x for AC watt meters). All calculated data, as
well as configuration parameters, are stored in internal 32-bit registers accessible through SPI or UART
peripheral. Three boards are available for evaluation purpose:
EVALSTPM34 board with 2 CT
EVALSTPM33 board with CT and shunt
EVALSTPM32 board with shunt
The main features of these boards are:
0.2% accuracy single-phase meter reference design
USB port for connection to the isolated hardware programmer STEVAL-IPE023V1 and PC GUI
RS232 and UART isolated port for connection to PC GUI
SPI/UART switch for device peripheral selection
2x programmable LEDs on-board
Digital expansion to external system-on-chip or MCU
Power supply 3.3 V: external or through the STEVAL-IPE023V1 isolated USB board
IEC61000 standard compliant

Contents
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Contents
1Overview ..........................................................................................3
1.1 Safety rules.......................................................................................4
1.2 Operating conditions.........................................................................4
1.3 Recommended readings...................................................................5
1.4 Getting technical support ..................................................................5
2EVALSTPM34, EVALSTPM33, EVALSTPM32 board......................6
2.1 Board description..............................................................................6
2.1.1 Hardware configuration ...................................................................... 6
2.1.2 Power supply...................................................................................... 6
2.1.3 Enable and reset ................................................................................ 6
2.1.4 Digital output....................................................................................... 7
2.1.5 SPI connection ................................................................................... 7
2.1.6 UART connection ............................................................................... 8
2.1.7 Metrology............................................................................................ 8
2.1.8 LED..................................................................................................... 9
2.1.9 Clock................................................................................................... 9
2.1.10 Voltage reference ............................................................................... 9
2.2 Connection to the line .......................................................................9
2.3 Board setup.....................................................................................12
2.3.1 Connection to PC GUI through the STEVAL-IPE023V1.................. 12
2.3.2 Connection to PC GUI through the RS232 port ............................... 12
2.4 The device basic configuration........................................................13
3Revision history ............................................................................14

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1 Overview
Figure 1: EVALSTPM34 board
Figure 2: EVALSTPM33 board

Overview
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Figure 3: EVALSTPM32 board
1.1 Safety rules
These boards can be connected to the mains voltage (230 V/110 V). In the case of
improper use, wrong installation or malfunction, there is a danger of serious personal injury
and damage to property. All operations such as: transport, installation, and commissioning,
as well as maintenance, should be carried out by skilled technical personnel (national
accident prevention rules must be observed) only.
1.2 Operating conditions
Table 1: Operating conditions
Parameter
Value
VNnominal voltage
230 VRMS
INnominal current
5 ARMS
Imax. maximum current
100 ARMS
CPconstant pulses
41600 imp/kWh
fline line frequency
50/60 Hz ± 10%
TOP operating temperature
-40/+85 °C

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1.3 Recommended readings
This document describes how to use and set up a basic test session with a GUI interface.
Additional information is available in the following documents:
STPM3x datasheet
AN4470
UM1719
EVALSTPM32 schematics
EVALSTPM33 schematics
EVALSTPM34 schematics
1.4 Getting technical support
All our customers receive free technical assistance through local ST distributor/office or by
visiting www.st.com; upgrades are also available free of charge on www.st.com/metering.
Customers should work with the latest version of software/firmware before contacting us.

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2.1 Board description
2.1.1 Hardware configuration
Table 2: EVALSTPM3x evaluation board setting and configuration terminals
Parameter
Value
J7
3.3 V external DC supply
J4
Device enable and reset
J5
Digital output pins
J6
SPI connector to the USB programmer/reader
J1
DB9 female connector for RS232 port
J2
UART isolated pin connector
J3
RS232 enable
J11a
VREF jumper
SWC1
DIP switch for SPI/UART peripheral selection
L1
Primary voltage
L2b
Secondary voltage
I1
Primary current
I2
Secondary current
2.1.2 Power supply
The board does not contain a power supply. VCC = 3.3 V DC supply should be provided
externally, by J7 connector. If the board is interfaced to PC by the STEVAL-IPE023V1
isolated dongle, it provides the board with supply. Since UART section is isolated, to use
either RS232 or J2 UART connectors, a different isolated 3.3 V supply must be provided
through J2 connector.
2.1.3 Enable and reset
The STPM3x enable pin should be shorted to VCC by keeping J4 jumper in EN position. To
reset the device, this jumper has to be in OFF position (GND).
a
For the EVALSTPM34 and the EVALSTPM33 board only.
b
For the EVALSTPM34 board only.

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2.1.4 Digital output
8-pin J5 connector provides all digital output pins of the device as listed in the below table:
Table 3: J5 connector pinout
Connector pin
STPM3x pin
1
INT1
2
INT2a
3
LED2
4
EN/RST
5
LED1
6
GND
7
CKIN/XTAL2
8
CKOUT/ZCR
2.1.5 SPI connection
To communicate with the device using the STEVAL-IPE023V1 isolated USB dongle, the
STPM3x SPI peripheral has to be selected. All SWC1 switches have to be in OFF position
before the device powers up. SPI pins are available in J6 connector for 10-pin flat cable
interfacing either to the STEVAL-IPE023V1 or to an external MCU.
Table 4: J6 SPI connector pinout
Name
Description
1
Not connected
2
MOSI
3
GND
4
MISO
5
SCS
6
SCL
7
Not connected
8
SYN
9
Not connected
10
VCC
The STEVAL-IPE023V1 provides isolation, while J6 pins are not isolated.
a
For the EVALSTPM34 and the EVALSTPM33 board only.

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2.1.6 UART connection
UART peripheral also communicates to the device. In this case, all SWC1 switches should
be in ON position when the device powers up. RS232 port is isolated from the board
through Si8621 transceiver to safely connect the board to PC; in this case, J3 jumper has
to be connected. UART isolated pins are also available on J2 connector for MCU
connection; in this case J3 jumper has to be disconnected. If UART connection is used, a
separate 3.3 VDC has to be provided to UART section.
Table 5: J2 UART connector
Name
Description
1
RXD
2
TXD
3
+3.3 VDC
4
GND
2.1.7 Metrology
Current sensing is performed by CT or shunt, while voltage is sensed by voltage
dividers.The EVALSTPM34 board has two currents and two voltage channels, while the
EVALSTPM33 has two currents and one voltage channel, the EVALSTPM32 has one
current and one voltage channel available. Main design parameters are listed in the below
table.
Table 6: EVALSTPM3x evaluation board parameters
Channel
Parameter
Value
Primary current
Current sensor sensitivity kSa
2.4 mV/A
Shunt sensor sensitivityb
0.3 mV/A
Primary voltage
R1voltage divider upper resistorc
810000 Ω
R2voltage divider upper resistor
470 Ω
Secondary currentd
kScurrent sensor sensitivity
2.4 mV/A
Secondary voltage
R1 voltage divider upper resistor
81000 Ω
R2 voltage divider upper resistor
470 Ω
Any
CPconstant pulse
41600 pulses/kWh
A 22 nF capacitor in parallel with R2 implements an antialiasing filter for voltage signal.
Regarding to current signal, the antialiasing filter is given by a 10 nF capacitor and 1 kOhm
resistors.
a
For the EVALSTPM34 board only.
b
For the EVALSTPM32 and EVALSTPM33 board only.
c
R1, R2 names do not refer to specific resistors on the schematic, but these names indicate voltage divider
resistors.
d
For the EVALSTPM34 and EVALSTPM33 board.

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2.1.8 LED
Two LEDs are connected to programmable LED pins of the device.
2.1.9 Clock
Clocking is provided to the board through 16 MHz quartz. 1 MOhm resistor and 15 pF
capacitors are used to filter noise.
2.1.10 Voltage reference
The STPM34 and STPM33 devices embed two internal independent voltage references.
J11 jumper shorts VREF, or it can be used to connect the external precision voltage
reference. The external reference should be connected between the desired VREF and
GND, if a single reference has to be used for both channels, VREF1 and VREF2 should be
shorted by J11.
2.2 Connection to the line
The board can be connected to line voltage and current in several ways, as shown in below
pictures.
Please note that, in boards using shunt, the shunt is at the same potential of voltage
neutral faston and therefore it is at the same potential of the board GND. When isolated
power sources are used or phantom loads, this is not important. In case of connection to
the mains, this has to be taken into account since, according to the wire connected to the
shunt, the board GND may be either at the 0 or 230 V potential.
Figure 4: Board connection to phantom load, dual-phase system (STPM34)

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Figure 5: Board connection to phantom load, single-phase system with neutral monitoring
(STPM34 and STPM33)
Figure 6: Board connection to phantom load, single-phase system (STPM3x)

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Figure 7: Board connection to isolated AC source (STPM34 and STPM33)
Figure 8: Board connection to mains

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2.3 Board setup
Regarding to the STPM3x evaluation software setup and use, please refer to user manual
UM1719.
The STEVAL-IPE023V1 is not included in the package, therefore it should be ordered
separately. Please read the user manual, before using it.
2.3.1 Connection to PC GUI through the STEVAL-IPE023V1
To evaluate the board using the STEVAL-IPE023V1 and the STPM3x evaluation software:
1. Put J4 enable jumper in EN position
2. Put SWC1 switches in OFF position, to "SPI serigraphy"
3. Connect J7 connector to 3.3 V DC isolated power supply, or put J4 jumper in the
STEVAL-IPE023V1 board in 1-2 position (supply voltage set to 3.3 V)
4. Connect the EVALSTPM3x board to either AC line or power source or phantom load as
shown in Section 2.1: "Board description", without powering it on
5. Connect the USB cable both to the STEVAL-IPE023V1 board and to PC
6. Connect the flat SPI cable from USB board to the EVALSTPM3x board
7. Power on AC source and DC source
8. Open GUI
9. When green LED on the STEVAL-IPE023V1 starts blinking, click "options", then
"interface", select "USB" and select the proper "serial port", baud rate is 19200
10. Now you can read, write, sample or calibrate the device
2.3.2 Connection to PC GUI through the RS232 port
To evaluate the board using a PC RS232 port and the STPM3x evaluation software:
1. Put J4 enable jumper in EN position
2. Put SWC1 switches in ON position, to "UART" serigraphy
3. Connect J7 connector and J2 connectors to 3.3 V DC separated and isolated power
supply
4. Enable RS232 port by inserting J3 jumper
5. Connect the EVALSTPM3x board to either AC line or power source or phantom load as
shown in Section 2.1: "Board description", without powering it on
6. Connect the serial cable both to the board and to PC
7. Power on AC source and DC source
8. Open GUI
9. Click "options", then "interface", select "UART" and select the proper "serial port", baud
rate is 9600
10. Now you can read, write, sample or calibrate the device

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2.4 The device basic configuration
During the startup, all internal device parameters are in the default value. For the
EVALSTPM34 board, primary channel gain GAIN[1:0] has to be changed to value 0
(current gain = x2), a correct energy measurement is, in this manner, assured. All other
parameters can be changed according to the needs (board calibration, phase-shift
compensation, desired output on the programmable pin). For further information on the
device configuration, please refer to the STPM3x datasheet.

Revision history
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Table 7: Document revision history
Date
Revision
Changes
16-Apr-2014
1
Initial release.
30-Sep-2015
2
Updated recommended readings, power supply, board setup and
the device basic configuration section.
Removed the schematic section.
Changed figure titled "Board connection to phantom load, single-
phase system (STPM3x)" and figure titled "Board connection to
isolated AC source (STPM34 and STPM33)".
Added figure titled "Board connection to mains".

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