STMICROELECTRONICS STPM01_11

STPM01
Programmable single phase energy metering IC
with tamper detection
Features
■
Active, reactive, apparent energies and RMS
values
■
Ripple free active energy pulsed output
■
Live and neutral monitoring for tamper
detection
■
Easy and fast digital calibration in only one
point over the whole current range
■
OTP for calibration and configuration
■
Integrated linear VREGs for digital and analog
supply
■
Selectable RC or crystal oscillator
■
Support 50 ÷ 60 Hz – IEC62052-11, IEC620532x specification
■
Less than 0.1 % error
■
Precision voltage reference: 1.23 V and 30
ppm/°C max
Description
The STPM01 is designed for effective
measurement of active, reactive and apparent
energy in a power line system using Rogowski
coil, current transformer and shunt sensors. This
device can be implemented as a single chip
monophase energy meter or as a peripheral
measurement in a microcontroller based
monophase or 3-phase energy meter. The
STPM01 consists, essentially, of two parts: the
analog part and the digital part. The former, is
composed by preamplifier and 1st order Δ ∑ A/D
converter blocks, band gap voltage reference, low
drop voltage regulator, the latter, is composed by
system control, oscillator, hard wired DSP and
SPI interface. There is also an OTP block, which
is controlled through the SPI by means of a
Table 1.
TSSOP20
dedicated command set. The configured bits are
used for testing, configuration and calibration
purpose. From a pair of Δ ∑ output signals coming
from analog section, a DSP unit computes the
amount of consummated active, reactive and
apparent energy, RMS and instantaneous values
of voltage and current. The results of computation
are available as pulse frequency and states on
the digital outputs of the device or as data bits in a
data stream, which can be read from the device
by means of SPI interface. This system bus
interface is used also during production testing of
the device and/or for temporary or permanent
programming of bits of internal OTP. In the
STPM01 an output signal with pulse frequency
proportional to energy is generated, this signal is
used in the calibration phase of the energy meter
application allowing a very easy approach. When
the device is fully configured and calibrated, a
dedicated bit of OTP block can be written
permanently in order to prevent accidental
entering into some test mode or changing any
configuration bit.
Device summary
Order code
Temperature range
Package
Packaging
STPM01FTR
- 40 to 85 °C
TSSOP20 (tape and reel)
2500 parts per reel
June 2011
Doc ID 10853 Rev 8
1/60
www.st.com
60
Contents
STPM01
Contents
1
Schematic diagram
......................................... 5
2
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4
Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6
Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1
Measurement error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.2
ADC offset error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.3
Gain error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.4
Power supply DC and AC rejection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.5
Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8
Theory of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1
General operation description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.2
Analog inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.3
∑Δ A/D converters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.4
Zero crossing detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.5
Period and line voltage measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.6
Single wire meter mode (only Rogowsky coil sensor) . . . . . . . . . . . . . . . 21
8.7
Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.8
Load monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.9
Error detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.10
Tamper detection module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.10.1
2/60
Detailed operational description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.11
Phase compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.12
Clock generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Doc ID 10853 Rev 8
STPM01
Contents
8.12.1
RC Startup procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.13
Resetting the STPM01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.14
Energy to frequency conversion (standalone) . . . . . . . . . . . . . . . . . . . . . 28
8.15
Driving a stepper motor (standalone) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8.16
Using STPM01 in microcontroller based meter (peripheral) . . . . . . . . . . 30
8.17
Status bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.18
Programming the STPM01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.19
Configuration bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.20
Mode signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
8.21
SPI interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
8.21.1
Remote reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
8.22
Reading data records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
8.23
Writing procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8.24
Energy calculation algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
8.24.1
Active power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.24.2
Reactive power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
8.24.3
Apparent power and RMS values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
9
STPM01 calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
10
Application design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
11
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
12
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Doc ID 10853 Rev 8
3/60
List of tables
STPM01
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Table 22.
4/60
Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Programmable pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Internal signal description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Gain of voltage and current channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Configuration of current sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Nominal voltage values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
No load detection thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Different settings for LED signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Configuration of MOP and MON pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
LED pin configuration in peripheral mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Status bit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Configuration bits map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Mode signals description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Working point settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Device constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Resistor divider ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Current channel typical components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Doc ID 10853 Rev 8
STPM01
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
Figure 29.
Figure 30.
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pin connections (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Supply current vs. supply voltage, TA = 25 °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
RC oscillator frequency vs. VCC, R = 12 kΩ, TA = 25 °C . . . . . . . . . . . . . . . . . . . . . . . . . . 15
RC oscillator: frequency jitter vs. temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Analog voltage regulator: line - load regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Digital voltage regulator: line - load regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Voltage channel linearity at different VCC voltages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Power supply AC rejection vs. VCC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Power supply DC rejection vs. VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Error over dynamic range gain dependence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Primary current channel linearity at different VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Gain response of ΔΣ AD converters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
First order ∑ Δ A/D converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
ZCR signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
LIN and BFR signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Bandgap temperature variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Timings of tamper module - Primary channel selected. . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Timings of tamper module - Secondary channel selected . . . . . . . . . . . . . . . . . . . . . . . . . 25
Different oscillator circuits (a): with quartz; (b): internal oscillator; (c): with external source27
Positive energy stepper driving signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Negative energy stepper driving signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
STPM01 data records map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Timing for providing remote reset request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Data records reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Timing for data records reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Timing for writing configuration and mode bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Active energy computation diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
STPM01 reference schematic with one current transformer and one shunt. . . . . . . . . . . . 54
STPM01 with 3X charge pump DC-DC converter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Doc ID 10853 Rev 8
5/60
Schematic diagram
STPM01
1
Schematic diagram
Figure 1.
Block diagram
6/60
Doc ID 10853 Rev 8
STPM01
Pin configuration
2
Pin configuration
Figure 2.
Pin connections (top view)
Table 2.
Pin description
Pin n°
Symbol
Type (1)
1
MON
PO
Programmable output pin, see Table 5
2
MOP
PO
Programmable output pin, see Table 5
3
SCS
D IN
Digital input/output pin, see Table 5
4
VDDD
A OUT
5
VSS
GND
Ground
6
VCC
P IN
Supply voltage
7
VOTP
P INr
Supply voltage for OTP cells
8
VDDA
A OUT
9
IIP1
A IN
Positive input of primary current channel
10
IIN1
A IN
Negative input of primary current channel
11
IIP2
A IN
Positive input of secondary current channel
12
IIN2
A IN
Negative input of secondary current channel
13
VIP
A IN
Positive input of voltage channel
14
VIN
A IN
Negative input of voltage channel
15
SYN
D I/O
Programmable input/output pin, see Table 5
Crystal oscillator input or resistor connection if RC oscillator is selected
Name and function
1.5 V Output of internal low drop regulator which supplies the digital core
3 V Output of internal low drop regulator which supplies the analog part
16
CLKIN
A IN
17
CLKOUT
A OUT
18
SCL/NLC
D I/O
Programmable input/output pin, seeTable 5
19
SDA/TD
D I/O
Programmable input/output pin, see Table 5
20
LED
DO
Programmable output pin, see Table 5
Oscillator Output (RC or crystal)
1. A: Analog, D: Digital, P: Power
Doc ID 10853 Rev 8
7/60
Maximum ratings
STPM01
3
Maximum ratings
Table 3.
Absolute maximum ratings
Symbol
Parameter
Value
Unit
-0.3 to 6
V
± 150
mA
-0.3 to VCC + 0.3
V
VCC
DC Input voltage
IPIN
Current on any pin (sink/source)
VID
Input voltage at digital pins (SCS, MOP, MON, SYN, SDATD,
SCLNLC, LED)
VIA
Input voltage at analog pins (IIP1, IIN1, IIP2, IIN2, VIP, VIN)
-0.7 to 0.7
V
VOTP
Input voltage at OTP pin
-0.3 to 25
V
ESD
Human body model (all pins)
± 3.5
kV
TOP
Operating ambient temperature
- 40 to 85
°C
Junction temperature
- 40 to 150
°C
Storage temperature range
- 55 to 150
°C
TJ
TSTG
Note:
Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these condition is not implied.
Table 4.
Thermal data
Symbol
RthJA
Parameter
Thermal resistance junction-ambient
1. This value is referred to single-layer PCB, JEDEC standard test board.
8/60
Doc ID 10853 Rev 8
Value
Unit
114.5 (1)
°C/W
STPM01
Functions
4
Functions
Table 5.
Programmable pin functions
Programmable
pin
Stand-alone mode
(APL register=2 or 3)
Peripheral mode
(APL register=0 or 1)
MON
Output for Stepper’s node (MB)
If APL=0 then Watchdog signal.
If APL=1 then ΔΣ signal of current channel
MOP
Output for Stepper’s node (MA)
If APL=0 then ZCR
If APL=1 then ΔΣ signal of voltage channel
LED
If APL=2 then LED provides high frequency
pulses proportional to Active Energy with 50%
duty cycle.
If APL=3 then LED provides pulses proportional
to Active Energy (internal signal AW). The
number of pulses per kWh can be selected
according to the value of KMOT configuration bit.
If APL=0 then LED can provide Active,
Reactive or Apparent Energy according to
value of KMOT configuration bit.
If APL=1 then LED is connected to the MUX
signal generated from the tamper detection
circuit.
When LED=low then the primary current
channel is selected, if LED=high the
secondary current channel is selected.
SCLNLC
SDATD
No-load indicator:
when low, a no-load condition is detected
Tamper indicator:
when low tamper condition is detected
SYN
Negative active power indicator:
when low a negative active power condition is
detected
SCS
Must be high to activate SCLNLC, SDATAD and
SYN indications
Doc ID 10853 Rev 8
Used for SPI interface (see SPI interface
section for details)
9/60
Functions
Table 6.
Symbol
STPM01
Internal signal description
Name
Description
ZCR
Zero crossing signal
Provides positive pulse every time the line voltage crosses zero
AW
Active energy
Pulse frequency signal proportional to active energy
RW
Reactive energy
Pulse frequency signal proportional to reactive energy
SW
Apparent energy
Pulse frequency signal proportional to apparent energy
LIN
Line frequency signal
This signal is high when the voltage channel value is rising and it is low when
the voltage channel is falling. Basically this signal is the sign of dv/dt.
Base frequency range
This signal is high when either the voltage line frequency is outside the
nominal band or the voltage register is below 64.
It is cleared when the voltage line frequency is inside the nominal band and
the voltage register goes above 128.
Stepper motor signals
Signal available in MOP and MON to drive a stepper motor
BIT
Tamper flag
This signal provides the information on the tamper status. If low no tamper is
detected, when high a tamper condition has been detected. This signal is part
of the status register but is also available on the SDATD pin when in
standalone mode.
BIL
No load condition
Provides information on the load condition. This signal is part of the status
register but is also available on the SCLNLC pin when in standalone mode.
BIL=1 no load condition, BIL=0 normal operation.
BFR
MA
MB
10/60
Doc ID 10853 Rev 8
STPM01
5
Electrical characteristics
Electrical characteristics
VCC = 5 V, TA = 25 °C, 100 nF to 1 uF between VDDA and VSS, 100 nF to 1 uF between VDDD
and VSS, 100 nF to 1 uF between VCC and VSS unless otherwise specified.
Table 7.
Electrical characteristics
Symbol
Parameter
Test conditions
Min.
Typ.
Max.
Unit
400
Hz
Energy measurement accuracy
fBW
Effective bandwidth
Limited by digital filtering
5
eAW
Accuracy of active power
Over 1 to 1000 of dynamic
range
0.1
%
eRW
Accuracy of reactive power
Over 1 to 1000 of dynamic
range
0.1
%
eSW
Accuracy of apparent power
Over 1 to 500 of dynamic range
0.1
%
SNR
Signal to noise ratio
Over the entire bandwidth
52
db
PSRRDC Power supply DC rejection
Voltage signal: 200 mVrms/50Hz
Current signal: 10 mVrms/50Hz
fCLK= 4.194 MHz
VCC=3.3V±10%, 5V±10%
0.2
%
PSRRAC Power supply AC rejection
Voltage signal: 200 mVrms/50Hz
Current signal: 10 mVrms/50Hz
fCLK= 4.194 MHz
VCC=3.3V+0.2Vrms1@100Hz
VCC=5.0V+0.2Vrms1@100Hz
0.1
%
5.5
V
General section
VCC
Operating supply voltage
ICC
Supply current configuration
registers cleared or device
locked (TSTD=1)
ΔICC
Increase of supply current per
configuration bit, during
programming
3.165
4 MHz, VCC = 5V
3
4
8 MHz, VCC = 5V
5
6
4 MHz, VCC = 5V
120
mA
µA/bit
Increase of supply current per
configuration bit with device
locked
4 MHz, VCC = 5V
2
2.5
V
POR
Power on reset on VCC
VDDA
Analog supply voltage
2.85
3.0
3.15
V
VDDD
Digital supply voltage
1.425
1.50
1.575
V
fCLK
Oscillator clock frequency
fLINE
VOTP
MDIV bit = 0
4.000
4.194
MHz
MDIV bit = 1
8.000
8.192
MHz
Nominal line frequency
45
65
Hz
OTP programming voltage
14
20
V
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Electrical characteristics
Table 7.
Symbol
Electrical characteristics (continued)
Parameter
IOTP
OTP programming current per
bit
tOTP
OTP programming time per bit
ILATCH
STPM01
Test conditions
Min.
Typ.
Max.
2.5
100
Unit
mA
300
µs
300
mA
-0.3
0.3
V
Gain 8X
-0.15
0.15
Gain 16X
-0.075
0.075
Gain 24X
-0.05
0.05
Gain 32X
-0.035
0.035
Current injection latch-up
immunity
Analog Inputs (IIP1, IIN1, IIP2, IIN2, VIP, VIN)
Voltage channel
VMAX
Maximum input signal levels
Current
channels
V
fADC
A/D Converter bandwidth
10
kHz
fSPL
A/D Sampling frequency
FCLK/4
Hz
VOFF
Amplifier offset
ZIP
VIP, VIN Impedance
Over the total operating voltage
range
ZIN
VIP1, VIN1, VIP2, VIN2
Impedance
Over the total operating voltage
range
GERR
IVL
ILEAK
100
Current channels gain error
±20
mV
400
kΩ
100
kΩ
±10
%
Voltage channel leakage current
-1
1
Channel disabled (PST=0 to 3;
CH2 disabled if CSEL=0; CH1
Current channel leakage current disabled if C
SEL=1) or device off
-1
1
Input enabled
µA
µA
-10
10
Digital I/O Characteristics (SDA, CLKIN, CLKOUT, SCS, SYN, LED)
SDA, SCS, SYN, LED
VIH
Input high voltage
VIL
Input low voltage
VOH
Output high voltage
IO = -2mA
VOL
Output low voltage
IO = +2mA
IUP
Pull up current
tTR
Transition time
CLKIN
0.75VCC
V
1.5
SDA, SCS, SYN, LED
0.25VCC
CLKIN
V
0.8
VCC-0.4
V
0.4
CLOAD = 50pF
V
15
µA
10
ns
Power I/O Characteristics (MOP, MON)
VOH
Output high voltage
IO = -14mA
VOL
Output low voltage
IO = +14mA
tTR
Transition time
CLOAD = 50pF
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Doc ID 10853 Rev 8
VCC-0.5
V
0.5
5
10
V
ns
STPM01
Table 7.
Electrical characteristics
Electrical characteristics (continued)
Symbol
Parameter
Test conditions
Min.
Typ.
Max.
Unit
1
µA
4
MΩ
Crystal oscillator (see circuit Figure 20)
II
Input current on CLKIN
RP
External resistor
CP
External capacitors
fCLK
Nominal output frequency
1
22
4
4.194
8
8.192
pF
MHz
RC oscillator (see circuit Figure 20)
ICLKIN
Settling current
RSET
Settling resistor
tJIT
Frequency jitter
40
fCLK= 4 MHz
60
µA
12
kΩ
1
ns
1.23
V
±1
%
On chip reference voltage
Reference voltage
VREF
TC
Reference accuracy
Temperature coefficient
After calibration
30
50
ppm/
°C
SPI interface timing
FSCLKr
Data read speed
32
MHz
FSCLKw
Data write speed
100
kHz
tDS
Data setup time
20
ns
tDH
Data hold time
0
ns
tON
Data driver on time
20
ns
tOFF
Data driver off time
20
ns
tSYN
SYN active width
2/fCLK
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s
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Terminology
6
Terminology
6.1
Measurement error
STPM01
The error associated with the energy measurement made by the STPM01 is defined as:
Percentage error = [STPM01 (reading) - true energy] / true energy
6.2
ADC offset error
This is the error due to the DC component associated with the analog inputs of the A/D
converters. Due to the internal automatic DC offset cancellation the STPM01 measurement
is not affected by DC components in voltage and current channel. The DC offset
cancellation is implemented in the DSP.
6.3
Gain error
The gain error is gain due to the signal channel gain amplifiers. This is the difference
between the measured ADC code and the ideal output code. The difference is expressed as
percentage of the ideal code.
6.4
Power supply DC and AC rejection
This parameter quantifies the STPM01 measurement error as a percentage of reading when
the power supplies are varied. For the PSRRAC measurement, a reading at two nominal
supplies voltages (3.3 and 5 V) is taken. A second reading is obtained with the same input
signal levels when an ac (200 mVRMS/100 Hz) signal is introduced onto the supplies. Any
error introduced by this ac signal is expressed as a percentage of reading.
For the PSRRDC measurement, a reading at two nominal supplies voltages (3.3 and 5V) is
taken. A second reading is obtained with the same input signal levels when the supplies are
varied ± 10 %. Any error introduced is again expressed as a percentage of the reading.
6.5
Conventions
The lowest analog and digital power supply voltage is named VSS which represent the
system ground (GND). All voltage specifications for digital input/output pins are referred to
GND.
Positive currents flow into a pin. Sinking current means that the current is flowing into the pin
and then it is positive. Sourcing current means that the current is flowing out of the pin and
then it is negative.
Timing specifications of signal treated by a digital control part are relative to CLKOUT. This
signal is provided from the crystal oscillator of 4.194 MHz nominal frequency or from the
internal RC oscillator, eventually an external source of 4.194 MHz or 8.192 MHz can be
used.
Timing specifications of signals of the SPI interface are relative to the SCLNLC, there is no
direct relationship between the clock (SCLNLC) of the SPI interface and the clock of the
DSP block. A positive logic convention is used in all equations.
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STPM01
Typical performance characteristics
7
Typical performance characteristics
Figure 3.
Supply current vs. supply voltage,
TA = 25 °C
Figure 4.
RC oscillator frequency vs. VCC,
R = 12 kΩ, TA = 25 °C
Figure 5.
RC oscillator: frequency jitter vs.
temperature
Figure 6.
Analog voltage regulator: line - load
regulation
Figure 7.
Digital voltage regulator: line - load Figure 8.
regulation
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Voltage channel linearity at
different VCC voltages
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Typical performance characteristics
Figure 9.
STPM01
Power supply AC rejection vs. VCC
Figure 11. Error over dynamic range gain
dependence
Figure 10. Power supply DC rejection vs. VCC
Figure 12. Primary current channel linearity at
different VCC
Figure 13. Gain response of ΔΣ AD converters
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STPM01
Theory of operation
8
Theory of operation
8.1
General operation description
The STPM01 is able to perform active, reactive and apparent energy measurements, RMS
and instantaneous values for voltage and current, line frequency information.
Most of the functions are fully programmable using internal configuration bits accessible
through SPI interface. The most important configuration bits are the two application bits
(APL - see Table 16 for configuration register). Using these bits the STPM01 can be
programmed as peripheral (APL = 0 or APL = 1) in microcontroller based meter systems or
as standalone meter device (APL = 2 or APL = 3).
In standalone mode, the STPM01 is able to drive a stepper motor with the MOP and MON
pins, while some of the SPI pins (see Table 5) are used to provide information on tamper, no
load and negative power.
In peripheral mode, due to the fact that the stepper motor is not used, the MOP and MON
pins are used to provide different information (see Table 5), while the SPI pins are used to
communicate with the microcontroller.
The STPM01 includes internal registers that hold the useful information for the meter
system. Two kinds of active energy are available: the total active energy that includes all
harmonic content called type 0 and the active energy limited to the 1st harmonic called type
1. This last energy value is obtained filtering the type 0 active energy. The resolution of both
the two active energies is 20-bit. Reactive and Apparent energies are also available with a
20-bit resolution.
STPM01 provides also the RMS values of voltage and current. Due to the modest dynamic
variation of the voltage, the RMS value is stored with a resolution of 11 bit. While the RMS
current value has a resolution of 16 bit. The momentary sampled value of voltage and
current are available also with a resolution of 11 and 16 bit respectively. The line frequency
value is stored with a resolution of 14 bits.
Due to the proprietary energy computation algorithm, STPM01 calibration is very easy and
fast allowing calibration in only one point over the whole current range. The calibration
parameters are stored permanently in the OTP (one time programmable) cells, preventing
calibration tampering.
8.2
Analog inputs
Input amplifiers
The STPM01 has one fully differential voltage input channel and two fully differential current
input channels.
The voltage channel consists of a differential amplifier with a gain of 4. The maximum
differential input voltage for the voltage channel is ± 0.3 V.
The two current channels are multiplexed (see tamper section for details) to provide a single
input to a preamplifier with a gain of 4. The output of this preamplifier is connected to the
input of a programmable gain amplifier (PGA) with possible gain selections of 2, 4, 6, 8. The
total gain of the current channels are then 8, 16, 24, 32. The gain selections are made by
writing to the gain register and it can be different for the two current channels. In case the
tamper function is not used, the secondary current can be disabled.
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Theory of operation
STPM01
The maximum differential input voltage is dependent on the selected gain according to the
following table.
Table 8.
Gain of voltage and current channels
Voltage channels
Gain
Current channels
Max Input voltage (V)
±0.30
4
Gain
Max input voltage (V)
8X
±0.15
16X
±0.075
24X
±0.05
32X
±0.035
The gain register is included in the device configuration register with the address names
PST and ADDG. The table below shows the gain configuration according to the register
values:
Table 9.
Configuration of current sensors
Primary
Gain
Secondary
Sensor
Gain
Configuration Bits
Sensor
8
16
PST (3 bits)
ADDG (1 bit)
0
0
0
1
1
0
1
1
Rogowsky Coil
24
Disabled (No Tamper)
32
8
CT
2
X
32
Shunt
3
X
4
0
4
1
8
8
16
16
Rogowsky Coil
Rogowsky Coil
24
24
5
0
32
32
5
1
8
8
CT
6
X
32
Shunt
7
X
CT
8
Note:
If the device is used in configuration PST = 7 (primary channel with CT, secondary channel
with Shunt), the shunt Ks must always be equal to one fourth of the current transformer Ks.
Both the voltage and current channels implement an active offset correction architecture
which gives the benefit to avoid any offset compensation.
The analog voltage and current signals are processed by the ∑ Δ Analog to digital
converters that feed the hardwired DSP. The DSP implements an automatic digital offset
cancellation that make possible avoiding any manual offset calibration on the analog inputs.
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STPM01
8.3
Theory of operation
∑Δ A/D converters
The analog to digital conversion in the STPM01 is carried out using two first order ∑ Δ
converters. The device performs A/D conversions of analog signals on two independent
channels in parallel. The current channel is multiplexed as primary or secondary current
channel in order to be able to perform a tamper function, if it is enabled. The converted ∑ Δ
signals are supplied to the internal hardwired DSP unit, which filters and integrates those
signals in order to boost the resolution and to yield all the necessary signals for
computations.
A ∑ Δ modulator converts the input signal into a continuous serial stream of 1 s and 0 s at a
rate determined by the sampling clock. In the STPM01, the sampling clock is equal to fCLK/4.
The 1-bit DAC in the feedback loop is driven by the serial data stream. The DAC output is
subtracted from the input signal. If the loop gain is high enough, the average value of the
DAC output (and therefore the bit stream) can approach that of the input signal level. When
a large number of samples are averaged a very precise value of the analog signal is
obtained. This averaging is carried out in the DSP section which implements decimation,
integration and DC offset cancellation of the supplied ∑ Δ signals. The gain of the
decimation filters is 1.004 for the voltage channel and 0.502 for the current channel. The
resulting signal has a resolution of 11bits for voltage channel and 16 bits for current
channel.
Figure 14. First order ∑ Δ A/D converter
f CLK/4
Integrator
+
Input analog signal
Output digital signal
Σ
∫
-
DAC
8.4
Zero crossing detection
The STPM01 has a zero crossing detector circuit on the voltage channel which can be used
by application for synchronization of some utility equipment to event of zero crossing of line
voltage. This circuit produces the internal signal ZCR which has a rising edge every time the
line voltage crosses zero and a negative edge every time the voltage reaches its positive or
negative peak. The ZCR signal is then at twice the line voltage frequency. The ZCR signal is
available on the MOP pin only when STPM01 works as peripheral with the configuration bit
APL = 0.
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Theory of operation
STPM01
Figure 15. ZCR signal
8.5
Period and line voltage measurement
The period module measures the period of the base frequency of the voltage channel and
checks if the voltage signal frequency is within the fCLK/217 to fCLK/215 band. To do this, the
LIN signal is produced, which is low when the line voltage is rising, and high when the line
voltage is falling. This means that the LIN signal is the sign of dv/dt. With further elaboration,
the ZCR signal is also produced. On the trailing edge of LIN (line frequency) the period
counter starts counting up pulses of the fCLK /4 reference signal. The LIN signal is available
on the status bit register (see Table 15).
If the counted number of pulses between two trailing edges of LIN is higher than 215, or if
the counting is never stopped (no LIN trailing edge) this means that the base frequency is
lower than fCLK/217 Hz and a BFR (base frequency range) error flag is set.
If the number of pulses counted between two trailing edges of LIN is lower than 213, the
base frequency exceeds the limit (means it is higher than fCLK/215. In this case, the error
must be repeated three consecutive times in order to set the BFR error flag.
For example, with a 4.194304 MHz oscillator frequency and MDIV bit clear (or 8.192 MHz
with MDIV set), fCLK/4 is 1048.576 MHz. If the line frequency is 30 Hz, the counted fCLK/4
pulses between two LIN trailing edges are 34952, more than 215 (32768 pulses). The BFR
low frequency limit is then:
fCLK/217 = 4194304/131072 = 32 Hz.
With the same clock frequency, if the line frequency is 130Hz, the fCLK/4 pulses between two
LIN trailing edges are 8066, more than 213 (8192). The BFR high frequency limit is then:
fCLK/215 = 4194304/32768 = 128 Hz.
When the line frequency re-enters the nominal band, the BFR flag is automatically reset.
This BFR error flag is also assembled as part of the 8-bit status register (see Table 15).
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STPM01
Theory of operation
Figure 16. LIN and BFR signal
The BFR flag is also set if the register value of the RMS voltage drops below 64. BFR is
cleared when the register value goes above 128. The BFR, then, also gives information
about the presence of the line voltage within the meter.
When the BFR error is set, the computation of power is zero unless the FRS bit is set or the
single wire mode operation is selected (see Section 8.6).
In fact, the effect of the BFR bit can be overridden by setting FRS configuration bit.
It means that if FRS is set and BFR is also set, all the energy computation is carried on as
BFR was cleared. In this case then p=u*i, where u could be zero or not (if BFR was set
because voltage RMS register value is below 64).
In standalone mode, the MOP, MON and LED provide the energy information, their
operation is not affected by FRS bit, it means that when BFR is set they stop switching
regardless the FRS value.
8.6
Single wire meter mode (only Rogowsky coil sensor)
STPM01 support single wire meter (SWM) operation when working with Rogowsky coil
current sensors. In SWM mode there is no available voltage information in the voltage
channel. It is possible that someone has disconnected one wire (live or neutral) of the meter
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Theory of operation
STPM01
for tampering purposes or in case the line voltage is very stable, it is possible to use a
predefined value for computing the energy without sensing it.
In order to enable the SWM mode, the STPM01 must be configured with PST values of 4 or
5, (tamper enabled-Rogowsky coils). In this way, if the BFR error is detected, STPM01
enters in SWM. If BFR is cleared the energy calculation is performed normally, when BFR is
set (no voltage information is available) the energy computation is carried out using a
nominal voltage value according to the NOM configuration bits.
Since there is no more information on the phase shift between voltage and current, the
apparent rather than active power is used for tamper and energy computation. The
calculated apparent energy is the product between IRMS (effectively measured) and an
equivalent VRMS that can be calculated as follows:
VRMS = VPK*KNOM,
where VPK represents the maximum line voltage reading of the STPM01 and KNOM is a
coefficient that changes according to the following table:
Table 10.
Nominal voltage values
NOM
KNOM
0
0.3594
1
0.3906
2
0.4219
3
0.4531
For example, if a R1 = 783 kΩ and R2 = 475 Ω are used as resistor divider when the line
voltage is present, the positive voltage present at the input of the voltage channel of
STPM01 is:
VI =
R2
⋅ VRMS 2
R1 + R2
since the maximum voltage value applicable to the voltage channel input of STPM01 is +0.3
V, the equivalent maximum line voltage applicable is:
VPK = R1+R2/R2 • 0.3 = 494.82
considering the case of NOM=2, the correspondent RMS values used for energy
computation are:
VRMS = VPK • 0.4219 = 208.76 [V]
Usually the supply voltage for the electronic meter is taken from the line voltage, in SWM,
since the line voltage is not present any more, some other power source must be used in
order to provide the necessary supply to STPM01 and the other electronic components of
the meter.
8.7
Power supply
The main STPM01 supply pin is the VCC pin. From the VCC pin two linear regulators provide
the necessary voltage for the analog part VDDA (3 V) and for the digital part VDDD (1.5 V).
The VSS pin represents the reference point for all the internal signals. 100 nF low ESR
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STPM01
Theory of operation
capacitor should be connected between VCC and VSS, VDDA and VSS, VDDD and VSS. All
these capacitors must be located very close to the device.
The STPM01 contains a power on reset (POR) detection circuit. If the VCC supply is less
than 2.5 V then the STPM01 goes into an inactive state, all the functions are blocked
asserting a reset condition. This is useful to ensure correct device operation at power-up
and during power-down. The power supply monitor has built-in hysteresis and filtering,
which give a high degree of immunity to false triggering due to noisy supplies.
A bandgap voltage reference (VBG) of 1.23 V ±1 % is used as reference voltage level
source for the two linear regulators and for the A/D converters. Also, this module produces
several bias currents and voltages for all other analog modules and for the OTP module. The
bandgap voltage can be compensated regardless to the temperature variations with the
BGTC bits.
Figure 17. Bandgap temperature variation
8.8
Load monitoring
The STPM01 includes a no load condition detection circuit with adjustable threshold. This
circuit monitors the voltage and the current channels and, when the measured voltage is
below the set threshold, the internal signal BIL becomes high. The information about this
signal is also available in the status bit BIL.
The no load condition occurs when the product between VRMS and IRMS register values is
below a given value. This value can be set with the LTCH configuration bits.
Four different no-load threshold values can be chosen according to the two configuration
bits LTCH (see Table 11).
Table 11.
No load detection thresholds
LTCH
KLTCH
0
800
1
1600
2
3200
3
6400
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Theory of operation
STPM01
When a no load condition occurs (BIL=1) the integration of power is suspended and the
tamper module is disabled.
In standalone mode, if a no load condition is detected, the BIL signal blocks generation of
pulses for stepper and forces SCLNLC pin to be low. If APL = 2 (see Section 8.14) the LED
pin continues providing the high frequency pulses, while if APL = 3, the pulses are stopped
as happens for MOP and MON.
In peripheral mode, the BIL signal can be accessed only through the SPI interface.
8.9
Error detection
In addition to the no load condition and the line frequency band, the integration of power can
be suspended also due to detected error on the source signals.
There are two kinds of error detection circuits involved. The first checks all the ∑ Δ signals
from the analog part if any is stacked at 1 or 0 within the 1/128 of fCLK period of observation.
In case of detected error the corresponding ∑ Δ signal is replaced with an idle ∑ Δ signal,
which represents a constant value 0. All error and other resolved flags are treated as bits of
a device status and can be read out by means of SPI interface.
Another error condition occurs if the MOP, MON and LED pin outputs signals are different
from the internal signals that drive them. This can occur if some of this pin is forced to GND
or to some other imposed voltage value. In this case the internal status bit PIN is activated
providing the information that some hardware problem has been detected, for example the
stepper motor has been mechanically blocked.
8.10
Tamper detection module
The STPM01 is able to measure the current in both live and neutral wire with a time domain
multiplexing approach on a unique sigma delta modulator. This mechanism is adopted to
implement anti-tamper function. If this function is selected (see Table 9), the live and neutral
wire currents are monitored; when the difference between the two measurements exceeds a
rated threshold the STPM01 enters the "tamper state", while in "normal state" the two
measurements are below the threshold.
In particular, both channels are not observed all the time, rather a time multiplex mechanism
is used. During the observation time of each channel, its active energy is calculated. A
tamper condition occurs when the absolute value of the difference between the two active
energy values is greater than a certain percentage of the averaged energy during the
activated tamper module (see Equation 1: ).
This percentage value can be selected between two different values (12.5 % and 6.25 %)
according to the value of the configuration bit CRIT.
The tamper condition is detected when the following formula is satisfied:
Equation 1
EnergyCH1 - EnergyCH2 > KCRIT (EnergyCH1 + EnergyCH2)/2;
where KCRIT can be 12.5 % or 6.25 %.
The detection threshold is much higher than the accuracy difference of the current channels,
which should be less than 0.2 %, but, some headroom should be left for possible transition
effect, due to accidental synchronism of actual load current change with the rhythm of taking
the energy samples.
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STPM01
Theory of operation
The tamper circuit works if the energies associated with the two current channels are both
positive or negative, if the two energies have different sign, the tamper is on all the time
however, the channel with the associated higher power is selected for the final computation
of energy.
In single wire mode, the apparent energy rather than the active is used for tamper detection.
When internal signals are not good enough to perform the calculations, i.e. line period is out
or range or ΔΣ signals from analog section are stacked at high or low logic level, or no load
condition is activated, the tamper module is disabled and its state is preset to normal.
8.10.1
Detailed operational description
The meter is initially set to normal state, i.e. tamper not detected.In this condition the
primary channel is selected for final integration of energy. In such state the values of both
load currents should not differ more than the accuracy difference of the channels does.
Sixty-four periods of line voltage is used as a tamper checking period.
After 24 periods of line voltage two internal signals MUX and INH are changed in order to
enable secondary current channel and to freeze the last power and RMS values of primary
current channel. The following 16 periods of line frequency are used for tamper detection
integration. During this gap, the final energy calculation does not use the signal from
selected channel but the frozen values.
Four line periods after the INH switch, the integration of power from secondary current
channel is started and lasts four periods. Additional four line periods later MUX signal is
switched back to primary current channel and the integration for tamper detection is started.
The timings of MUX and INH signals are shown in Figure 18 below.
Figure 18. Timings of tamper module - Primary channel selected
MUX
Ch 1
Ch 2
Ch 1
Ch 1
INH
Tamper power integrators
Cycles
B
24
4
4
A
4
4
24
When the secondary channel is selected to be integrated by the final energy integrator, the
MUX and INH signals change according to Figure 19 below.
Figure 19. Timings of tamper module - Secondary channel selected
This means that energy of four periods from secondary channel followed by energy of four
periods from primary channel is sampled within the tamper module. From these two
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Theory of operation
STPM01
samples, called B and A respectively, the criteria of tamper is calculated and the channel
with higher current is selected, resulting in a new tamper state. If four consecutive new
results of criteria happen, i.e. after elapsed 5.12 s at 50 Hz, the meter will enter into tamper
state. Thus, the channel with the higher current will be selected for the energy calculation. If
samples of power A and B would have different signs, the Tamper would be on all the time
but, the channel with bigger power would be still selected for the final integration of energy.
If a tamper status has been detected, the multiplex ratio will be 56:8 if the primary channel
energy is greater than the secondary one, otherwise it will be 8:56.
The detected tamper condition is stored in the BIT status bit. If BIT = 0 tamper is not
detected, if BIT = 1 a tamper condition has been detected. In standalone mode the BIT flag
is also available in the SDATD pin.
8.11
Phase compensation
The STPM01 is does not introduce any phase shift between voltage and current channel.
However, the voltage and current signals come from transducers, which could have inherent
phase errors. For example, a phase error of 0.1° to 0.3° is not uncommon for a current
transformer (CT). These phase errors can vary from part to part, and they must be corrected
in order to perform accurate power calculations. The errors associated with phase mismatch
are particularly noticeable at low power factors. The STPM01 provides a means of digitally
calibrating these small phase errors through a introducing delays on the voltage or current
signal. The amount of phase compensation can be set using the 4 bits of the phase
calibration register (CPH).
The default value of this register is at value of 0 which gives 0° phase compensation. When
the 4 bits give a CPH of 15 (1111) the introduced compensation is +0.576°. This
compensates the phase shift usually introduced by the current sensor, while the voltage
sensor, normally a resistor divider, does not introduce any delay. The resolution step of the
phase compensation is 0.038°.
8.12
Clock generator
All the internal timing of the STPM01 is based on the CLKOUT signal. This signal can be
generated in three different ways:
1.
RC: this oscillator mode can be selected using the RC configuration bit. If RC = 1 the
STPM01 will run using the RC oscillator. A resistor connected between CLKIN and
ground will set the RC current. For 4 MHz operation the suggested settling resistor is
12 kΩ; The oscillator frequency can be compensated using the CRC configuration bit
(see Table 16)
2.
Quartz: If RC = 0 the oscillator will work with an external crystal. The suggested circuit
is depicted in Figure 20;
3.
External clock: keeping RC=0, it is also possible to feed the CLKOUT pin with an
external oscillator signal
The clock generator is powered from analog supply and is responsible for two tasks. The
first one is to retard the turn on of some function blocks after POR in order to help smooth
start of external power supply circuitry by keeping off all major loads.
The second task of the clock generator is to provide all necessary clocks for analog and
digital parts. Within this task, the MDIV configuration bit is used to inform the device about
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Theory of operation
the nominal frequency value of CLKOUT. Two nominal frequency ranges are expected, from
4.000 MHz to 4.194 MHz (MDIV = 0) or from 8.000 MHz to 8.192 MHz (MDIV = 1).
Figure 20. Different oscillator circuits (a): with quartz; (b): internal oscillator; (c): with external
source
8.12.1
RC Startup procedure
To use the device with RC oscillator the configuration bit RC (see Table 16) must be set.
Since the default configuration is for a crystal oscillator, when a RC oscillator is used instead
and the device is supplied for the very first time it is not internally clocked and consequently
the DSP is inactive. In this condition it is not possible to set RC or any other configuration bit.
The following SPI procedure can be run in order to set the RC bit and provide the clock to
the device:
●
Set the mode signal BANK;
●
Perform a software reset;
●
Read the registers: BANK mode signal should be checked and the records should
show something (not 000000F0);
●
Set the mode signal RD;
●
Read the registers through SPI just to check that RD mode signal has been set;
●
Clear the mode signal BANK;
●
DO NOT perform a reading, and write configuration bit RC;
In this way the RC oscillator is started. If the registers are read again, it can be seen that RD
and RC bits are set, and BANK is cleared.
Once the RC startup procedure is complete, the device is clocked and active and it is
possible to permanently write the RC bit.
For details on mode signals refer to Chapter 8.20, for SPI operations refer to Chapter 8.21.
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Theory of operation
8.13
STPM01
Resetting the STPM01
The STPM01 has no reset pin. The device is automatically reset by the POR circuit when
the VCC crosses the 2.5 V value but it can be reset also through the SPI interface giving a
dedicated command (see SPI section for remote reset command details).
In case of reset caused by POR circuit all clocks and both DC buffers in the analog part are
kept off for about 30 ms and all blocks of digital part, except for SPI interface, which is hold
in a reset state for about 125 ms after a reset condition.
When the reset is performed through SPI no delayed turn on is generated.
Resetting the STPM01 causes all the functional modules of STPM01 to be cleared including
the OTP shadow latches (see paragraph 16 for OTP shadow latches description).
The reset through SPI (remote reset request) will normally take place during production
testing or in an application of meter with some on-board microprocessor when some
malfunction of metering device will be detected.
8.14
Energy to frequency conversion (standalone)
When used in standalone mode the STPM01 provides energy to frequency conversion both
for calibration and energy readout purposes. In fact one convenient way to verify the meter
calibration is to provide a pulse train signal with 50 % duty cycle whose frequency signal is
proportional to the active energy under steady load conditions. In this case the user will
choose a certain number of pulses on the LED pin that will corresponds to 1 kWh. We will
name this value as P.
The active energy frequency-based signal is available in the LED pin when APL = 2 or APL
= 3.
If APL = 2 the LED is driven from internal signal AW (active energy) whose frequency is
proportional to the active energy. The signal AW is taken from the 11th bit of the active
energy register, consequently a relationship between the LSB value of the active energy
register and the number of pulses provided per each kWh (P) can be defined as.
kAW = 1000/(211•P) [Wh]
If APL = 3 the LED pin provides active energy frequency-based signal dependent on the
value of the KMOT configuration bit according to the following table. In this case the pulses
will have a fixed width of 31.25 ms.
Table 12.
Different settings for LED signal
APL=2
APL=3
Pulses
Pulses
KMOT (2 Bits)
0
P/64
1
P/128
P
2
P/32
3
P/256
Due to the innovative and proprietary power calculation algorithm the frequency signal is not
affected by any ripple at twice the line frequency, this feature strongly reduces the
calibration time of the meter.
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Theory of operation
In a practical example where APL = 2, and the desired P is 64000 pulses/kWh (= 17.7
Hz*kW), we have:
KAW = 7.63*10-6 Wh
This means that the reading of 0x00001 in the active energy register represents 7.63 µWh,
while 0xFFFFF represents 8 Wh.
8.15
Driving a stepper motor (standalone)
When used in standalone mode (APL = 2 or APL = 3), the STPM01 is able to directly drive a
stepper motor. From signal AW, a stepper driving signals MA and MB are generated by
means of internal divider, mono-flop and decoder. The MA and MB signals are brought to
the MOP and MON pins that are able to drive the stepper motor. Several kinds of selections
are possible for the driving signals according to the configuration bits LVS and KMOT.
The numbers of pulses per kWh (PM) in the MOP and MON outputs are linked with the
number of pulses of the LED P (see previous paragraph) pin with the following relationship:
Table 13.
Configuration of MOP and MON pins
LVS (1 Bit)
KMOT (2 Bits)
Pulses length
PM
0
0
31.25 ms
P/64
0
1
31.25 ms
P/128
0
2
31.25 ms
P/32
0
3
31.25 ms
P/256
1
0
156.25 ms
P/640
1
1
156.25 ms
P/1280
1
2
156.25 ms
P/320
1
3
156.25 ms
P/2560
The mono-flop limits the length of the pulses according to the LVS bit value.
The decoder distributes the pulses to MA and MB alternatively, which means that each of
them has only a half of selected frequency.
Negative power is computed with its own sign, and the MOP and MON signals invert their
logic state in order to make the backward rotation direction of the motor. See the diagram
below.
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Theory of operation
STPM01
Figure 21. Positive energy stepper driving signals
Hi
MON
Lo
Hi
MOP
Lo
Figure 22. Negative energy stepper driving signals
Hi
MON
Lo
Hi
MOP
Lo
When a no-load condition is detected MOP and MON are held low.
8.16
Using STPM01 in microcontroller based meter (peripheral)
The higher flexibility of STPM01 allows its use in very high end microcontroller based energy
meters. In this case the STPM01 must be programmed to work in peripheral mode, all the
SPI pins (SCS, SCLNCL, SDATD, SYN) are used only for communication purposes allowing
the microcontroller to write and read the internal STPM01 registers. The peripheral mode
has two further different configuration modes according to the status of the APL
configuration bit. The APL bit status changes the function of MOP, MON and LED pins
according to the description below.
APL = 0:
In the MOP pin, the ZCR signal is available (see paragraph 3 for details about ZCR signal);
The pin MON provides the DOG signal. The DOG signal generates a 16 ms long positive
pulse every 1.6 seconds. Generation of these pulses can be suspended if data are read in
intervals shorter than 1.6 s. The DOG signal is actually a watchdog reset signal which can
be used to control an operation of an on-board microcontroller. It is set to high whenever the
VDDA voltage is below 2.5 V, but after VDDA goes above 2.5 V this signal starts to run.
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Theory of operation
It is expected that an application microcontroller should access the data in the metering
device on regular basis at least 1/s (recommended is 32/s). Every latching of results in the
metering device requested from the microcontroller also resets the watchdog. If latching
requests does not follow each other within 1.6 second, an active high pulse on MON is
produced, because device assumes that microcontroller does not operate properly. An
application can use this signal either to control the RESET pin of its microcontroller or it can
be tied to some interrupt pin. The last possibility is recommended for a battery backup
application which can enter some sleep mode due to power down condition and should not
be reset by metering device because it would exit from the sleep mode.
The LED pin can be driven from AW wide band (active energy as in standalone mode), AW
limited at fundamental, RW (reactive energy) or SW (apparent energy) according to the
value of KMOT bit.
Table 14.
LED pin configuration in peripheral mode
KMOT (2 Bits)
Signal available in LED pin
# of Pulses
0
AW Type 0
(1)
P [kWh]
1
AW Type 1 (1)
P [kWh]
2
RW
P [kVARh]
3
SW
P [kVAh]
1. * Type0 is the Wide band Active Energy and Type1 is the fundamental Active Energy if FUND=0, if FUND=1 they are
swapped.
In this case, since the LED pin is driven by signals different from AW, some other
relationship between the LSB of the register and must be defined:
KAWFund = 4*KAW [Wh]
KRW = 2*KAW [VARh]
KSW = KAW [VAh]
APL = 1:
MOP provides the ∑ Δ signal generated from the analog voltage input;
MON provides the ∑ Δ signal generated from the analog current input, according to the
selection of the tamper module
LED provides the information about the selection of the current channel made by the tamper
module. If LED is low it means the primary channel is selected, if LED is high the secondary
channel is actually selected.
8.17
Status bits
The STPM01 includes 8 status bits that provide several information on the current meter
status. The status bits are the following:
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Theory of operation
Table 15.
STPM01
Status bit description
Bit #
Name
0
BIL
Description
Condition
BIL=0: No load condition not detected
No load condition
BIL=1: No load detected
1
BCF
∑ Δ signals status
2
BFR
Line frequency range
BCF=0: ∑ Δ signals alive
BCF=1: one or both ∑ Δ signals are stacked
BFR=0: Line frequency inside the 45Hz-65Hz range
BFR=1: Line frequency out of range
BIT=0: Tamper not detected;
3
BIT
Tamper condition
BIT=1: Tamper detected;
MUX=0: Primary current channels selected by the tamper module;
4
MUX
Current channel selection MUX=1: Secondary current channels selected by the tamper
module;
LIN=0: line voltage is going from the minimum to the maximum value.
(Δv/Δt >0);
5
LIN
Trend of the line voltage
LIN=1: line voltage is going from the maximum to the minimum value.
(Δv/Δt < 0);
PIN=0: the output pins are consistent with the data
6
PIN
Output pins check
7
HLT
Data Validity
PIN=1: the output pins are different with the data, this means some
output pin is forced to 1 or 0.
HLT=0: the data records reading are valid.
HLT=1: the data records are not valid. A reset occurred and a restart
is in progress.
When STPM01 is used in peripheral mode all these signal can be read through the SPI
interface. See paragraph 16 for details on the Status bit location in the STPM01 data
records.
In standalone mode the BIL signal is available in SCLNLC pin and the BIT signal in the
SDATD pin. All the other signals can be read only through SPI interface.
8.18
Programming the STPM01
Data records
The STPM01 has 8 internal data records registers. Every data record consists of 4-bit parity
code and 28-bit data value where the parity code is computed from the data value, which
makes total of 32 bits or 4 bytes.
The figure below shows the data records structure with the name of the contained
information.
Each bit of parity nibble is defined as odd parity of all seven corresponding bits of data
nibbles.
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Theory of operation
The first 6 registers are read-only except for the 8 bit mode signals in the DFP register (the
mode signals will be described later in this paragraph). The last two registers CFL and CFH
can be also written because they contain the configuration bits. Among these last 64 bits (32
of CFL and 32 of CFH), 8 bits are used for parity nibbles, then only 56 bits are used for
configuring and programming the STPM01.
Figure 23. STPM01 data records map
20 bit
4 bit
8 bit
1bit 1bit
1bit
6 bit
DAP
parity
type0 active energy
DRP
parity
reactive energy
DSP
parity
apparent energy
lower f(u)
DFP
parity
type 1 energy
mode signals
DEV
parity
p
uRMS
iRMS
DMV
parity
p
uMOM
iMOM
CFL
parity
lower part of configurators
parity
upper part of configurators
CFH
Status
0
msb
upper f(u)
lsb
11 bit
8.19
1
16 bit
Configuration bits
All the configuration bits that control the operation of the device (CFL and CFH data records)
can be written in a temporary or permanent way. In case of temporary writing the
configuration bits value are written in the so called shadow registers which are simple
latches that hold the configuration data. In case of permanent writing the configuration bits
are stored in the OTP (one time programmable) cells that keep the information for an
undefined period of time even if the STPM01 is without supply, but, once written, they
cannot be changed anymore.
The shadow registers are cleared whenever a reset condition occurs (both POR and remote
reset).
As indicated in the data records table, the configuration bits are 56. Each of them consists of
paired elements, one is latch, the OTP shadow, and another is the OTP antifuse element.
When the STPM01 is released in the market, all antifuses represents logic low state but they
can be written by the user in order to configure the STPM01.This means that STPM01 can
retain 56 bits of information even if it has been unsupplied for an undefined time. That’s why
the CFG signals are used to keep certain configuration and calibration values of device.
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Theory of operation
STPM01
The very first CFG bit, called TSTD, is used to disable any change of system signals after it
was permanently set. During the configuration phase, each bit set to logic level 1 will
increase the supply current of STPM01 of about 120 µA, until the TSTD bit is set to 1. The
residual increase of supply current is 2 µA per each bit set to 1. It is then recommended to
set the TSTD bit to 1 after the configuration procedure in order to keep the supply current as
low as possible.
The STPM01 can work either using the data stored in the OTP cells either the data available
in the shadow latches. This can be chosen according to the value RD Mode signal (see
mode signal paragraph for description). If the RD is set, the CFG bits originates from
corresponding OTP shadow latches otherwise, if the RD is cleared, the CFG bits originates
from corresponding OTP antifuses. This way one can temporary sets up certain
configuration or calibration of device then verify it and then change it, if it is necessary. For
example, this is extensively exercised during production tests.
Each configuration bit can be written sending a byte command to STPM01 through its SPI
interface. The procedure to write the configuration bits is described in the SPI section.
After the TSTD bit has been set, the only write commands accepted will be the precharge
and the remote reset, this implies that the shadow latches cannot be used as source of
configuration data anymore.
Table 16.
Configuration bits map
Address
Name
n. of
bits
0
TSTD
1
Test mode and OTP write disable:
- TSTD=0: testing and continuous pre-charge of OTP when in read mode,
- TSTD=1:normal operation and no more writes to OTP
000001
1
MDIV
1
Measurement frequency range selection:
- MDIV=0: 4.000MHz to 4.194MHz,
- MDIV=1: 8.000MHz to 8.192MHz
000010
2
RC
1
Type of internal oscillator selection:
- RC=0:crystal oscillator,
- RC=1:RC oscillator
000011
3
4 (1)
2
000100
Peripheral or Standalone mode:
- APL=0: peripheral, MON=WatchDOG; MOP=ZCR, LED=pulses,
- APL=1: peripheral, MOP=ΔΣ Voltage; MON=ΔΣ current; LED=Mux (current) APL=2: standalone, MOP,MON=stepper, LED=pulses, SCLNLC=no load
condition, SDATD=tamper detected, SYN=negative active power direction
- APL=3: standalone, MOP:MON=stepper, LED=pulses according to KMOT,
SCLNLC=no load condition, SDATD=tamper detected, SYN=negative active
power direction
6-bit
binary
DEC
000000
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APL
Description (1)
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STPM01
Theory of operation
Table 16.
Configuration bits map (continued)
Address
n. of
bits
Description (1)
PST
3
Current channel sensor type, gain and tamper selection:
- PST=0: primary is coil x8 (x16 if ADDG=1), secondary is not used, no tamper
- PST=1: primary is coil x24 (x32 if ADDG=1), secondary is not used, no tamper
- PST=2: primary is CT x8, secondary is not used, no tamper
- PST=3: primary is shunt x32, secondary is not used, no tamper
- PST=4: primary is coil x8 (x16 if ADDG=1), secondary is coil x8 (x16 if
ADDG=1), tamper
- PST=5: primary is coil x24 (x32 if ADDG=1), secondary is coil x24 (x32 if
ADDG=1), tamper
- PST=6: primary is CT x8, secondary is CT x8, tamper
- PST=7: primary is CT x8, secondary is shunt x32, tamper
Name
6-bit
binary
DEC
000101
5
000110
6
000111
(1)
7
001000
8
FRS
1
Power calculation when BFR=1 and PST≠4,5 (no single wire mode)
- FRS=0: energy accumulation is frozen, power is set to zero;
- FRS=1: normal energy accumulation and power computation (p=u*i);
001001
9
MSBF
1
Bit sequence output during record data reading selection:
- MSBF=0: msb first
- MSBF=1: lsb first
1
This bit swap the information stored in the type0 (first 20 bits of DAP register)
and type1 (first 20 bits of DFP register) active energy.
- FUND = 0: type 0 contains wide band active energy, type1 contains
fundamental active energy
- FUND = 1: type 0 contains fundamental active energy, type1 contains wide
band active energy
1
RESERVED
2
No load condition threshold as product between VRMS and IRMS:
LTCH=0
800
LTCH=1
1600
LTCH=2
3200
LTCH=3
6400
001010
10
001011
11
001100
12
001101 13 (1)
001110
FUND
LTCH
Constant of stepper pulses/kWh (see par. 16) selection when APL=2 or 3:
If LVS=0,
KMOT=0
P/64
KMOT=1
P/128
KMOT=2
P/32
KMOT=3
P/256
14
If LVS=1,
KMOT
001111 15 (1)
2
KMOT=0
KMOT=1
KMOT=2
KMOT=3
P/640
P/1280
P/320
P/2560
Selection of pulses for LED when APL=0:
KMOT=0
Type0 Active Energy
KMOT=1
Type1 Active Energy
KMOT=2
Reactive Energy
KMOT=3
Apparent Energy
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Theory of operation
Table 16.
STPM01
Configuration bits map (continued)
Address
Name
6-bit
binary
DEC
010000
16
RESERVED
BGTC
2
Bandgap Temperature compensation bits. See Figure 17 for details.
CPH
4
4-bit unsigned data for compensation of phase error, 0°+0.576°.
16 values are possible with a compensation step of 0.0384°. When CPH=0 the
compensation is 0°, when CPH=15 the compensation is 0.576°.
8
8-bit unsigned data for voltage channel calibration.
256 values are possible. When CHV is 0 the calibrator is at -12.5 % of the
nominal value. When CHV is 255 the calibrator is at +12.5 %. The calibration
step is then 0.098%.
8
8-bit unsigned data for primary current channel calibration.
256 values are possible. When CHP is 0 the calibrator is at -12.5 % of the
nominal value. When CHP is 255 the calibrator is at +12.5 %. The calibration
step is then 0.098%.
8
8-bit unsigned data for secondary current channel calibration.
256 values are possible. When CHS is 0 the calibrator is at -12.5 % of the
nominal value. When CHS is 255 the calibrator is at +12.5 %. The calibration
step is then 0.098 %.
18
010011 19 (1)
010100
20
010101
21
010110
Description (1)
2
010001 17 (1)
010010
n. of
bits
22
010111 23 (1)
011000
24
011001
25
011010
26
011011
27
011100
28
011101
29
011110
30
CHV
011111 31 (1)
100000
32
100001
33
100010
34
100011
35
100100
36
100101
37
100110
38
CHP
100111 39 (1)
101000
40
101001
41
101010
42
101011
43
101100
44
101101
45
101110
46
CHS
101111 47 (1)
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Theory of operation
Table 16.
Configuration bits map (continued)
Address
Name
6-bit
binary
DEC
110000
48
110001 49 (1)
110010
n. of
bits
CRC
2
2-bit unsigned data for calibration of RC oscillator.
CRC=0, or CRC=3 cal=0%
CRC=1, cal=+10%;
CRC=2, cal=-10%.
NOM
2
2-bit modifier of nominal voltage for Single Wire Meter.
NOM=0: KNOM=0.3594 / NOM=1: KNOM=0.3906 / NOM=2: KNOM=0.4219 /
NOM=3: KNOM=0.4531;
50
110011 51 (1)
Description (1)
110100
52
ADDG
1
Selection of additional gain on current channels:
ADDG=0: Gain+=0 / ADDG=1: Gain+=8
110101
53
CRIT
1
Selection of tamper threshold:
CRIT =0: 12,5% / CRIT =1: 6,25%
110110
54
LVS
1
Type of stepper selection:
LVS=0: pulse width 31.25 ms, 5V, / LVS=1: pulse width, 156.25 ms, 3V
110111
55
1
Reserved
1. IMPORTANT: This bit represents the MSB of the decimal value indicated in the description column.
As it is indicated above, the STPM01 includes 56 CFG bits. Normally, some of these bits
should be permanently set during production of application of STPM01 in order to protect
the application from power fails. Of course, if an application would include an on-board
microcontroller, it could reload the configuration and calibration values after power on restart
and so, the permanent set of STPM01 would not be necessary. But this is not very safe way
to do it, because due to some EMI even imposed to tamper the meter, the microcontroller
may become lost and during such state, it can change some system signals in the STPM01
or somebody can change the calibration and configuration by changing the software of onboard microcontroller.
8.20
Mode signals
The STPM01 includes 8 mode signals located in the DFP data record, 3 of these are used
only for internal testing purposes while 5 are useful to change some of the operation of the
STPM01. The mode signals are not retained when the STPM01 supply is not available and
then they are cleared when a POR occurs but they are not cleared when a remote reset
command (RRR) is sent through SPI.
The mode signals bit can be written using the normal writing procedure of the SPI interface
(see SPI section).
Of course, we can clear the RD by clearing all system signals. The first way is to generate
POR signal but this way we clear and reset the whole device. An alternative way is to set the
TSTD bit in the shadow latches. This setting becomes effective after SCS goes to idle state
when the TSTD clears all system signals including itself but, it does not reset the whole
device.
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Theory of operation
Table 17.
STPM01
Mode signals description
Bit #
Signal
name
0
BANK
Bit
value
Status
0
Reserved
3
Reserved
4
CSEL
5
6
7
0111000x
70 or 71
1111000x
F0 or F1
0
MOP and MON operates normally
0111001x
72 or 73
1
MOP and MON provides the driving signals to implement a
charge-pump DC-DC converter
1111001x
F2 or F3
0
Current Channel 1 selected when tamper is disabled
0111100x
78 or 79
1
Channel 2 selected when tamper is disabled
1111100x
F8 or F9
0
The 56 Configuration bits originated by OTP antifuses
0111101x
7A or 7B
1
The 56 Configuration bits originated by shadow latches
1111101x
FA or FB
0
Any writing in the configuration bits is recorded in the
shadow latches
0111110x
7C or 7D
1
Any writing in the configuration bits is recorded both in the
shadow latches and in the OTP antifuse elements
1111110x
FC or FD
1
Swap the 32 bits data records reading. From
1,2,3,4,5,6,7,8, to 5,6,7,8,1,2,3,4 and viceversa
1111111x
FF
PUMP
2
Hex
command
Used for RC startup procedure
1
1
Binary
command
RD
WE
Precharge
– RD mode signal has been already described in the SPI section but there is another
implied function of the signal RD. When it is set, each sense amplifier is disconnected
from corresponding antifuse element and this way, its 3 V NMOS gate is protected
from the high voltage of VOTP during permanent write operation. This means that as
long as the VOTP voltage reads more than 3 V, the signal RD should be set.
– PUMP: when set, the PUMP mode signal transform the MOP and MON pins to act as
driving signals to implement a charge-pump DC-DC converter (see schematic page
36). This feature is useful in order to boost the VCC supply voltage of the STPM01 to
generate the VOTP voltage (14 V to 20 V) needed to program the OTP antifuse
elements.
– CSEL In normal operation, if the anti-tamper module is not activated (see PST
configuration bits) the STPM01 will select the channel 1 as source of current
information. For debug or calibration purposes it is possible to select channel 2 as
source of current channel signal when the tamper module is disabled. This is done
setting CSEL mode bit.
– WE (write enable): This mode signal is used to permanently write to the OTP antifuse
element. When this bit is not set, any write to the configuration bit is recorded in the
shadow latches. When this bit is set the writing is recorded both in the shadow latch
and in the OTP antifuse element.
– Precharge: this command swaps the sequence of data record read, allowing the
reading of the last four data records as first and the first four as second. The reading
sequence will be 5, 6, 7, 8, 1, 2, 3, 4. Differently from the other mode signals, the
precharge command is not retained inside the STPM01, in fact it should be sent each
time before the reading of the data records. This is the only command that can be
sent to STPM01 when the TSTD bit has been set.
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Theory of operation
– BANK: it is used to activate RC oscillator (see Chapter 8.12.1).
8.21
SPI interface
The SPI interface supports a simple serial protocol, which is implemented in order to enable
a communication between some master system (microcontroller or PC) and the device.
Three tasks can be performed with this interface:
- remote resetting the device,
- reading data records,
- writing the Mode bits and the configuration bits (temporarily or permanently);
Four pins of the device are dedicated to this purpose: SCS, SYN, SCLNCN, SDATD. SCS,
SYN and SCLNLC are all input pins while SDATD can be input or output according if the SPI
is in write or read mode. A high level signal for these pins means a voltage level higher than
0.75 x VCC, while a low level signal means a voltage value lower than 0.25 x VCC.
The internal register are not directly accessible, rather a 32 bit of transmission latches are
used to pre-load the data before being read or written to the internal registers.
The condition in which SCS, SYN and SCLNLC inputs are set to high level determines the
idle state of the SPI interface and no data transfer occurs.
– SCS: as already described in the document, when STPM01 is in standalone mode,
the SYN, SCLNLC and SDATD are used also for providing information on the meter
status (see Table 5) and are not used for SPI communication. The SCS pin allows
using the above pins for SPI communication even when the STPM01 is working in
standalone mode, in fact SCS pin enables SPI operation when low. In this section, the
SYN, SCLNLC and SDATD operation as part of the SPI interface is described.
– SYN: this pin operates different functions according to the status of SCS pin. When
SCS is low the SYN pin status select if the SPI is in read (SYN=1) or write mode
(SYN=0). When SCS is high and SYN is also high the results of the input or output
data are transferred to the transmission latches.
– SCLNLC: it is basically the clock pin of the SPI interface. This pin function is also
controlled by the SCS status. If SCS is low, SCLNCL is the input of serial bit
synchronization clock signal. When SCS is high, SCLNLC is also high determining
the idle state of the SPI.
– SDATD is the Data pin. If SCS is low, the operation of SDATD is dependent on the
status of SYN pin. if SYN is high SDATD is the output of serial bit data (read mode) if
SYN is low SDATD is the input of serial bit data signal (write mode). If SCS is high
SDATD is input of idle signal.
Any pin above has internal weak pull up device of nominal 15 µA. This means that when
some pin is not forced by external signals, the state of pin is logic high. A high state of any
input pin above is considered as an idle (not active) state. For the SPI to operate correctly
the STPM01 must be correctly supplied as described in the power supply section. Idle state
of SPI module is recognized when the signals of pins SYN, SCS, SCLNLC and SDATD are
in a logic high state. Any SPI operations should start from such idle state. The exception to
this rule is when STPM01 has been put into mode of standalone application. In such mode it
can happen that states of pins SCLNLC, SDATD and SYN are not high due to states of
corresponding internal status bits.
When SCS is active (low), signal SDATD should change its state at trailing edge of signal
SCLNLC and the signal SDATD should be stable at next leading edge of signal SCLNLC.
The first valid bit of SDATD is always started with activation of signal SCLNLC.
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Theory of operation
8.21.1
STPM01
Remote reset
The timing diagram of the operation is shown on the Figure 24. The time step can be as
short as 30 ns.
The internal reset signal is named RRR. Unlike the POR, the RRR signal does not cause
the 30 ms retard restart of analog module and the 120 ms retard restart of digital module.
This signal doesn’t clear the mode signals.
Figure 24. Timing for providing remote reset request (1)
SCS
SYN
SCLNLC
SDATD
t1 t2 t3 t4
t5 t6
t7
t8
t9
t10
1. All the time intervals must be longer than 30 ns. t7 → t8 is the reset time, this interval must be longer than 30 ns as well.
8.22
Reading data records
Data records reading will take place most often when there will be an on-board
microcontroller in an application. Such microcontroller will be able to read all measurement
results and all system signals (configuration, calibration, status, mode). Again, the time step
can be as short as 30 ns. There are two phases of reading, called latching and shifting.
Latching is used to sample results into transmission latches. The transmission latches are
the flip-flops that hold the data in the SPI interface. This is done with the active pulse on
SYN when SCS is idle. The length of pulse on SYN must be longer than 2 periods of
measurement clock, i.e. more than 500 ns at 4 MHz.
The shifting starts when SCS become active. In the beginning of this phase another, but
much shorter pulse (30 ns) on SYN should be applied in order to ensure that an internal
transmission serial clock counter is reset to zero. An alternative way is to extend the pulse
on SYN into the second phase of reading. After that reset is done, a 32 serial clocks per
data record should be applied. Up to 8 data records can be read this way. This procedure
can be aborted at any time by deactivation of SCS (see Figure 24).
The first read out byte of data record is least significant byte (LSB) of data value and of
course, the fourth byte is most significant byte (MSB) of data value. Each byte can be further
divided into a pair of 4-bit nibbles, most and least significant nibble (MSN, LSN). This
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Theory of operation
division makes sense with the MSB of data value because the MSN of it holds the parity
code rather than useful data.
Figure 25. Data records reconstruction
The sequence of data record during the reading operation is fixed. Normally, an application
will read 1st,.., 6th data record, the 7th and 8th data record would read only when it need to
fetch the configuration data. However, an application may apply a precharge command (see
Table 17) prior reading phase. This command forces the device to respond with the
sequence 5th,.., 8th, 1st,.., 4th. Such change of sequence can be used to skip the first four
data records.
The timing diagram of the reading operation is shown on the Figure 26. One can see the
latching and beginning of shifting phase of the first byte (0x5F) of the first data record and
end of reading. Also, both alternatives to reset the internal transmission serial clock counter
is shown in signal SYN.
Figure 26. Timing for data records reading
SCS
f(read)
SYN
SCLNLC
SDATD
1st byte
last bit of 32nd byte
t1
t2
t3t4 t5
t6
t7 t8
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Theory of operation
STPM01
t1 → t2: Latching phase. Interval value > 2/fCLK
t2 → t3: Data latched, SPI idle. Interval value > 30 ns
t3 → t4: Enable SPI for read operation. Interval value > 30 ns
t4 → t5: Serial clock counter is reset. Interval value > 30 ns
t5 → t6: SPI reset and enabled for read operation. Interval value > 30 ns
t7: Internal data transferred to SDATD
t8: SDATD data is stable and can be read
The system that reads the data record from the STPM01 should check the integrity of each
data record. If the check fails, the reading should be repeated, but this time only the shifting
should be applied otherwise a new data would be latched into transmission latches and
incorrectly read one would be lost.
Normally, each byte is read out as most significant bit (MSB) first. But this can be changed
by setting the MSBF configuration bit in the STPM01 CFL data record. If this is done, each
byte is read out as least significant bit (LSB) first.
8.23
Writing procedure
Each writable bit (configuration and mode bits) has its own 6-bit absolute address. For the
configuration bits, the 6-bit address value corresponds to its decimal value, while for the
mode bits the addresses are the ones indicated in the Mode Signal paragraph.
In order to change the state of some latch one must send to STPM01 a byte of data which is
normal way to send data via SPI. This byte consists of 1-bit data to be latched (MSB),
followed by 6-bit address of destination latch, followed by 1-bit don’t care data (LSB) which
makes total 8 bits of command byte.
For example, if we would like to set the configuration bit 47 (part of the secondary current
channel calibrator) to 0, we must convert the decimal 47 to its 6-bit binary value: 101111.
The byte command will be then composed like this:
1 bit DATA value+6-bits address+1 bit (0 or 1) as depicted in Figure 27. In this case the
binary command will be 01011111 (0x5F) which is the one depicted in the figure or
01011110 (0x5E).
Figure 27. Timing for writing configuration and mode bits
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STPM01
Theory of operation
t1 → t2 (> 30 ns): SPI out of idle state
t2 → t3 (> 30 ns): SPI enabled for write operation
t3: data value is placed in SDA
t4: SDA value is stable and shifted into the device
t3 → t5 (> 10 µs): writing clock period
t3 → t5: 1 bit data value
t5 → t6: 6 bits address of the destination latch
t6 → t7: 1 bit EXE command
t8: end of SPI writing
t9: SPI enters idle state
The same procedure should be applied for the mode signals, but in this case the 6-bits
address must be taken from the Table 17.
The LSB of command is also called EXE bit because instead of data bit value, the
corresponding serial clock pulse is used to generate the necessary latching signal. This way
the writing mechanism does not need the measurement clock in order to operate, which
makes the operation of SPI module of STPM01 completely independent from the rest of
device logic except from the signal POR.
Commands for changing system signals should be sent during active signals SCS and SYN
as it is shown in the Figure 27. The SYN must be put low in order to disable SDATD output
driver of STPM01 and make the SDATD as an input pin. A string of commands can be send
within one period of active signals SCS and SYN or command can be followed by reading
the data record but, in this case, the SYN should be deactivated in order to enable SDATD
output driver and a SYN pulse should be applied before activation of SCS in order to latch
the data.
Interfacing the standard 3-wire SPI with STPM01 SPI.
Due to the fact a 2-wire SPI is implemented in STPM01 it is clear that sending any
command from a standard 3-wire SPI would require 3-wire to 2-wire interface, which should
produce a proper signal on SDATD from host signals SDI, SDO and SYN. A single gate 3state buffer could be omitted by an emulation of SPI just to send some command. On a
microcontroller this would be done by the following steps:
1.
disable the SPI module;
2.
set SDI pin which is connected to SDATD to be output;
3.
activate SYN first and then SCS;
4.
apply new bit value to SDI and activate SCL;
5.
deactivate SCL;
6.
repeat the last two steps seven times to complete one byte transfer;
7.
repeat the last three steps for any remaining byte transfer;
8.
set SDI pin to be input;
9.
deactivate SCS and the SYN;
10. enable the SPI module;
In case of precharge command (0xFF), emulation above is not necessary. Due to the pull up
device on the SDATD pin of the STPM01 the processor needs to perform the following
steps:
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Theory of operation
STPM01
1.
activate SYN first in order to latch the results;
2.
after at least 1µs activate SCS;
3.
write one byte to the transmitter of SPI (this will produce 8 pulses on SCL with SDI=1);
4.
deactivate SYN;
5.
optionally read the data records (the sequence of reading will be altered;
6.
deactivate SCS;
Permanent writing of the CFG bits
In order to make a permanent set of some CFG bits, the following procedure should be
conducted:
1.
collect all addresses of CFG bits to be permanently set into some list;
2.
clear all OTP shadow latches;
3.
set the system signal RD;
4.
connect a current source of at least +14 V, 1 mA to 3 mA to VOTP;
5.
wait for VOTP voltage is stable;
6.
set one OTP shadow latch from the list;
7.
set the system signal WE;
8.
wait for 300 µs;
9.
clear the system signal WE;
10. clear the OTP shadow latch which was set in step 6;
11. until all wanted CFG bits are permanently set, repeat steps 5 to 11;
12. disconnect the current source;
13. wait for VOTP voltage is less than 3 V;
14. clear the system signal RD;
15. read all data records, in the last two of them there is read back of CFG bits;
16. if verification of CFG bits fails and there is still chance to pass, repeat steps 1 to 16.
For steps of set or clear apply the timing shown in Figure 27 with proper signal on the
SDATD. For step 15 apply the timing shown in Figure 26.
For permanent set of the TSTD bit, which will cause no more writing to the Configuration
bits, the procedure above must be conducted in such way that steps 6 to 13 are performed
in series during single period of active SCS because the idle state of SCS would make the
signal TSTD immediately effective which in turn, would abort the procedure and possibly
destroy the device due to clearing of system signal RD and so, connecting all gates of 3V
NMOS sense amplifiers of already permanently set CFG bits to the VOTP source.
8.24
Energy calculation algorithm
Inside the STPM01 the computing section of the measured active power uses a completely
new signal patented process approach. This approach allows the device to reach high
performances in terms of accuracy.
The signals, coming from the sensors, for the instantaneous voltage:
Equation 2
v(t) = V•sin ωt; where V is the peak voltage and ω is related to the line frequency
and the instantaneous current:
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STPM01
Theory of operation
Equation 3
i(t) = I • sin (ωt + ϕ);
where I is the peak current, ω is related to the line frequency and ϕ is the phase difference
between voltage and current.
8.24.1
Active power
Figure 28. Active energy computation diagram
In the STPM01, after the pre-conditioning and the A/D conversion, the digital voltage signal
(which is dynamically more stable with respect to the current signal) is processed by a
differentiated stage which transforms:
Equation 4
v(t) → v’(t) = dv/dt = V ⋅ ω ⋅ cos ωt − [see Figure 28 - 5]
The resulted signal, together with the pre-processed and digitalized current signal:
Equation 5
i(t) = I ⋅ sin(ωt + ϕ); [see Figure 28 - 6]
are then available for the calculation process. These digital signals are also provided into
two additional stages which perform the integration of themselves, obtaining:
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Theory of operation
STPM01
Equation 6
dv/dt → v(t) = V ⋅sin ωt; [see Figure 28 - 7]
i(t) →
∫
I( t ) = i( t ) ⋅ dt = −
I
⋅ cos( ω t + ϕ )
ω
[see Figure 28 - 8]
Now four signals are available. Combining (pairing) them by means of two multiplying stages
two results are obtained:
Equation 7
p/ 1(t) =
dv
V ⋅ I ⋅ cos ϕ V ⋅ I ⋅ cos( 2ωt + ϕ)
⋅ i(t) ⋅ dt = −
−
dt
2
2
∫
[see Figure 28 - 9]
Equation 8
p/ 2 ( t) = v(t) ⋅ i(t) =
V ⋅ I ⋅ cos ϕ V ⋅ I ⋅ cos( 2ωt + ϕ)
−
2
2
[see Figure 28 - 10]
After these two operations, another stage performs the subtraction between the results p2
and p1 and a division by 2, obtaining the active power:
Equation 9
(p ( t ) − p/ 1( t )) V ⋅ I ⋅ cos ϕ
p( t ) = / 2
=
2
2
[see Figure 28 - 11]
In this way, the AC part V•I•cos(2ωt + ϕ)/2 has been then removed from the instantaneous
power.
In the case of current sensors like “Rogowski coils”, which provide the rate of the
instantaneous current signal (di/dt), the initial voltage signal differentiated stage will be
switched off. In this case the signals coming from the A/D conversion and their consequent
integrations will be:
Equation 10
v(t) = V•sin ωt
i′( t ) =
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di( t )
= −I ⋅ ω ⋅ cos( ω t + ϕ )
dt
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STPM01
Theory of operation
Equation 11
∫
V(t) = v(t) ⋅ dt = −
V
⋅ cos ωt
ω
Equation 12
[
(t) =
∫ i′( t ) ⋅ dt
= i( t ) = − I ⋅ sin( ω t + ϕ )
The signals process flow will be the same as shown in the previous case, and even with the
formulas above, the result will be the same.
The absence of any AC component allows a very fast calibration procedure: it requires just
to set (using the internal device programming registers) the voltage and current sensor
conversion constants, using the effective voltage and current (VRMS, IRMS) readings
provided by the device built-in communication port, avoiding the time-averaged readings of
the active power or need for line synchronization.
8.24.2
Reactive power
The reactive power is produced using the already computed signals. In case of shunt sensor
the voltage signal is derived while the current signal is not. A first computation is to multiply
DS value of integrated voltage channel with the value of integrated current channel, which
yields:
Equation 13
Q 1( t ) =
⎛
⎞
∫ v ′( t )dt ⋅ I( t ) =v ( t ) ⋅ I( t ) = ( V sin ω t ) ⋅ ⎜⎝ − ω cos( ω t + ϕ ⎟⎠ = 2 ω ⋅ (sin ϕ − sin( 2 ω t + ϕ ) )
I
VI
The second is to multiply filtered DS value of voltage channel with the value of filtered
current channel,
Equation 14
Q 2 (t) = v′(t) ⋅ i( t) = Vω cos ωt ⋅ I sin(ωt + ϕ) =
VI
⋅ ω ⋅ (sin ϕ + sin(2ωt + ϕ))
2
From the above results, Q1(t) is proportional to 1/ω while Q2(t) is proportional to ω. The
correct reactive power would result from the following formula:
Equation 15
Q=
1
1 VI
⋅ Q1(t) ⋅ ω + Q2 (t) ⋅ =
sin ϕ
2
ω 2
Since the above computation would need significant additional circuitry, the Reactive Power
in the STPM01 is calculated using only the Q1(t) multiplied by ω, it means:
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Theory of operation
STPM01
Equation 16
Q 3 ( t) =
1
VI
⋅ Q1(t) ⋅ ω =
⋅ (sin ϕ − sin(2ωt + ϕ))
2
2
The reactive power will present then a ripple at twice the line frequency. Since the average
value of a sinusoid is 0, this ripple does not contribute to the reactive energy calculation over
time, moreover, in the STPM01 the reactive power is not used for meter calibration or to
generate the stepper pulses, then this ripple will not affect the overall system performances.
In case of Rogowsky coil, the same procedure is applied, but the current channel will be
proportional to the derived of the current and the differentiated is bypassed in the voltage
channel, so we have:
Equation 17
Q 1( t ) =
⎛
⎞
∫ v( t)dt ⋅ ∫ i′(t)dt =V(t) ⋅ i(t) = ⎜⎝ − ω cos( ωt) ⎟⎠ ⋅ (− I sin( ωt + ϕ)) = 2ω (sin ϕ + sin( 2ωt + ϕ))
V
VI
Equation 18
Q1( t) = v( t) ⋅ i′(t) = V sin ωt( t) ⋅ (− Iω cos( ωt + ϕ)) = −
VI
⋅ ω ⋅ (sin ϕ − sin( 2ωt + ϕ))
2
The reactive power is then calculated:
Equation 19
Q3 (t) =
8.24.3
1
VI
⋅ Q1(t) ⋅ ω =
⋅ (sin ϕ + sin(2ωt + ϕ))
2
2
Apparent power and RMS values
The RMS values are calculated starting from the following formulas.
Shunt or current transformer
Equation 20
1
T
T
∫I
0
2
( t ) dt =
I
ω⋅
2
multiplying Equation 20 by ω, the IRMS value is obtained:
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Theory of operation
Equation 21
I
IRMS =
2
The RMS voltage value is obtained as:
Equation 22
1
T
VRMS =
T
∫v
2
V
( t )dt =
2
0
For the apparent power another value is produced:
Equation 23
1
T
T
∫ v′
2
( t )dt =
V ⋅ω
2
0
Multiplying Equation 20: and Equation 23: , the apparent power is produced:
Equation 24
S=
I
ω⋅ 2
⋅
V⋅ω
2
=
VI
2
Rogowsky coil
In this case we have:
Equation 25
IRMS =
1
T
T
∫ i′′
0
2
( t )dt =
I
2
while VRMS is calculated as in Equation 22: .
The apparent power is simple calculated multiplying Equation 25: and Equation 22: .
The DSP then performs the integration of the computed powers into energies. These
integrators are implemented as up/down counters and they can rollover. 20-bit output buses
of the counters are assigned as most significant part of energy data records. It is a
responsibility of an application to read the counters at least every second not to miss any
rollover.
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STPM01 calibration
9
STPM01
STPM01 calibration
Energy meters based on STPM01 device are calibrated in a fast and easy way. The
calibration is essentially based on the single calibration of the voltage and current channel
considering their RMS values rather than on the frequency of output pulse signal. When the
two channel are calibrated all the other measurement are calibrated too. This allows the
calibration to be performed in only one point shortening the production time of the meter.
This procedure is possible due to the below key points:
– Device is compound of two independent meter channels for line voltage and current
respectively. Each channel includes its own digital calibrator, to adjust the RMS in the
range of ±12.5 % in 256 steps, and digital filter, to remove any signal DC component.
All final results are not subject to calibration procedure because they are achieved
from such corrected signals by mathematical modules implemented by hardwired
DSP.
– Device computes different kind of energies: active, reactive and apparent. The active
energy is produced without 2nd harmonic of line frequency. It also computes RMS
values of measured voltage and current.
– Device produces an energy output pulse signal but information can also be read
through serial port interface, SPI, and communication channel.
– Device has an embedded memory, 56 bits, used for configuration and calibration
purposes. The value of these bits can be read or they can be changed temporarily or
permanently through SPI communication channel.
Let’s consider the basic information needed to start the calibration procedure:
Table 18.
Working point settings
Line RMS voltage
Vn
(230V)
Line RMS current
In
(5A)
Power sensitivity
P
(LED: P=128000 pulses/kWh, stepper motor: PM=P/64= 2000 pulses/kWh)
Shunt sensor
KS
0,42 mv/A
The following typical STPM01 parameters and constants are also known:
Table 19.
Device constants
Parameter
Internal reference voltage
VBG
Value
Tolerance
1.23 V
± 2%
2
23
Hz
± 50 ppm
Internal calculation frequency
fM
Amplification of voltage ADC
AV
4
± 1%
Amplification of current ADC
AI
8, 16, 24, 32
± 2%
Gain of differentiator
GDIF
0,6135
Gain of integrator
GINT
0,815
Gain of decimation filter
GDF
1.004
RMS voltage register length
BV
211
RMS current register length
BI
216
DUD
217
Constant
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STPM01 calibration
As shown in Table 18, only analog parameter are object of calibration because introduce a
certain error. Voltage ADC amplification Av is constant, while Ai is chosen according to used
sensors.
The calibration algorithm will firstly calculate the voltage divider ratio and, as final result, the
correction parameters, called Kv and Ki, which applied to STPM01 voltage and current
measures compensate small tolerances of analog components that affect energy
calculation.
Since Kv and Ki calibration parameters are the decimal representation of the corresponding
configuration bytes CHV and CHP or CHS (respectively voltage channel, primary current
channel and secondary current channel calibration bytes), at the end of calibration CHV and
CHP or CHS (according to the current channel under calibration, primary or secondary
respectively) bits' values are obtained.
In the following procedure CHV, CHP and CHS will be indicated as Cv and Ci.
Through hardwired formulas Kv and Ki tune measured values varying from 0,75 to 1 in 256
steps, according to the value of Cv and Ci (from 0 to 255).
To obtain the greatest correction dynamic initially calibrators are set in the middle of the
range, thus obtaining a calibration range of 12.5 % per voltage or current channel:
Calibrator’s value
Kv = Ki = 0.875
Ci = Cv = 128
In this way it is possible to tune Kv and Ki having a precise measured: for example Cv = 0
generates a correction factor of -12.5 % (Kv = 0.75) and Cv = 255 determines a correction
factor of +12.5 % (Kv = 1), and so on.
According to what pointed out above, the following formulas, which relate Kv, i and Cv, i are
obtained:
Kv,i = (Cv,i/128) * 0.125 + 0.75
Cv,i = 1024 * Kv,i - 768.
The calibration procedure will output Cv and Ci values that will allow the above power
sensitivity of the meter.
This sensitivity is used to calculate target frequency at LED pin for nominal voltage and
current values:
XF = f * 64;
with:
f = PM * In * Vn / 3600000;
From values above and for both chosen amplification factor AI=32 and initial calibration data,
the following target values can be calculated:
Target RMS reading for given In:
XI = In * KS * AI * Ki * GINT * GDF * GDIF * BI / (VBG * 1000) = 1573
Target RMS reading for given Vn:
XV = f * BV * BI * DUD / (fM * XI) = 852
The output of the voltage divider is then:
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STPM01 calibration
STPM01
VDIV = (XV * VBG)/ (2 * GDIF * AV * Kv * GDF * GINT * BV)= 145,6 mV
Choosing R2 = 500 Ω (connected between VI and VSS), the R1 resistor (connected between
VLINE and VIP) value is obtained:
R1 = R2 * (Vn - VDIV) / VDIV = 789,3 Ω
Indicating with IA and VA the real readings on the STPM01 RMS registers of voltage and
current, and with XI and XV ideal values of RMS current and voltage readings already
calculated, the final values for calibrators can be calculated as:
XV = (Kv * VA) / 0.875
XI = (Ki * IA) / 0.875
If the computed final calibration data would fall out of calibration data range, the energy
meter should be recognized as bad or the given presumptions and calculations above
should be checked. Otherwise, if the final data of calibrators would be written into energy
meter, the RMS readings should be very close to target values I and V and the frequency of
LED output should be very close to target value f.
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10
Application design
Application design
The choice of the external components in the transduction section of the application is a
crucial point in the application design, affecting the precision and the resolution of the whole
system.
Among the several considerations, a compromise has to be found between the following
needs:
1.
Maximize the signal to noise ratio in the voltage channel,
2.
Choose the current to voltage conversion ratio Ks and the voltage divider ratio in a way
that calibration can be achieved (please refer to AN2299)
3.
Choose Ks to take advantage of the whole current dynamic range according to desired
maximum current and resolution.
To maximize the signal to noise ratio of the current channel the voltage divider resistors ratio
should be as close as possible to those shown in Table 20.
Table 20.
Resistor divider ratio
Function
Component
Line voltage interface
Resistor divider
Parameter
Value
R to R ratio VRMS=230V
1650
R to R ratio VRMS=110V
830
Unit
V/V
The Figure 29 below shows a reference schematic for an application with the following
properties:
●
P = 64000 imp/KWh
●
INOM = 5 A
●
IMAX = 60 A.
Typical values for the current sensors sensitivity, also used in the reference schematic
below, are shown in Table 21.
Table 21.
Current channel typical components
Function
Component
Parameter
Current shunt
Line current interface
Current transformer
Unit
0.425
Current to voltage conversion ratio Ks
Rogowsky coil
Note:
Value
1.7
mV/A
0.13
If the device is used in configuration PST = 7 (primary channel with CT, secondary channel
with Shunt), the shunt Ks must always be equal to one fourth of the current transformer Ks.
Additional considerations on the application design, suggestions for noise and crosstalk
reduction can be found in the AN2317.
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Application design
STPM01
Figure 29. STPM01 reference schematic with one current transformer and one shunt
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Doc ID 10853 Rev 8
STPM01
Application design
Figure 30. STPM01 with 3X charge pump DC-DC converter
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Package mechanical data
11
STPM01
Package mechanical data
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK® is an ST trademark.
56/60
Doc ID 10853 Rev 8
STPM01
Package mechanical data
TSSOP20 mechanical data
mm.
inch.
Dim.
Min.
Typ.
Max.
A
Min.
Typ.
Max.
1.2
A1
0.05
A2
0.8
b
0.047
0.15
0.002
0.004
0.006
1.05
0.031
0.039
0.041
0.19
0.30
0.007
0.012
c
0.09
0.20
0.004
0.0079
D
6.4
6.5
6.6
0.252
0.256
0.260
E
6.2
6.4
6.6
0.244
0.252
0.260
E1
4.3
4.4
4.48
0.169
0.173
0.176
1
e
0.65 BSC
K
0°
L
0.45
A
0.0256 BSC
0.60
8°
0°
0.75
0.018
8°
0.024
0.030
A2
A1
b
K
e
L
E
c
D
E1
PIN 1 IDENTIFICATION
1
0087225C
Doc ID 10853 Rev 8
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Package mechanical data
STPM01
Tape & reel TSSOP20 mechanical data
mm.
inch.
Dim.
Min.
A
Max.
Min.
330
13.2
Typ.
Max.
12.992
C
12.8
D
20.2
0.795
N
60
2.362
T
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Typ.
0.504
22.4
0.519
0.882
Ao
6.8
7
0.268
0.276
Bo
6.9
7.1
0.272
0.280
Ko
1.7
1.9
0.067
0.075
Po
3.9
4.1
0.153
0.161
P
11.9
12.1
0.468
0.476
Doc ID 10853 Rev 8
STPM01
Revision history
12
Revision history
Table 22.
Document revision history
Date
Revision
Changes
28-Sep-2004
1
Preliminary data.
22-Dec-2005
2
Document updated.
24-Oct-2006
3
The chapter 9 updated.
06-Feb-2006
4
Modified Figure 11.
12-Jan-2009
5
Modified address 11 Table 16 on page 34.
03-Apr-2009
6
Modified Figure 20 on page 27.
19-Oct-2010
7
Added Chapter 8.12.1: RC Startup procedure on page 27, Chapter 10:
Application design on page 53, modified Chapter 8.10: Tamper detection
module on page 24, Chapter 8.5: Period and line voltage measurement on
page 20.
09-Jun-2011
8
Modified: Table 7 on page 11.
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STPM01
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