STPM14 STMicroelectronics, STPM14 Datasheet - Page 10

• Manufacturer Part Number: STPM14
• Description: (STPM11 - STPM14) Single phase energy metering IC
• Manufacturer: STMicroelectronics

Terminology
5
5.1
5.2
5.3
5.4
5.5
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Terminology
Measurement error
The error associated with the energy measured by STPM1X is defined as:
Percentage Error = [STPM1X (reading) - True Energy] / True Energy
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 STPM1X measurement
is not affected by DC components in voltage and current channel. The DC offset
cancellation is implemented in the DSP.
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
a percentage of the ideal code.
Power supply DC and AC rejection
This parameter quantifies the STPM1X measurement error as a percentage of the reading
when the power supplies are varied. For the PSRR
nominal supply voltages (3.3 and 5 V) is taken. A second reading is obtained with the same
input signal levels when an ac (200 mV
voltages. Any error introduced by this ac signal is expressed as a percentage of reading.
For the PSRR
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.
Conventions
The lowest analog and digital power supply voltage is named V
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 is positive. Sourcing current means that the current is flowing out of the pin and is
negative.
The timing specifications of the signal treated by digital control are relative to CLK
signal is provided by from the crystal oscillator of 4.194MHz nominal frequency or by the
internal RC oscillator. An external source of 4.194MHz or 8.192MHz can be used.
The timing specifications of signals of the CFGI interface are relative to the SCL-NLC, there
is no direct relationship between the clock (SCL-NLC) of the CFGI interface and the clock of
the DSP block.
A positive logic convention is used in all equations.
DC
measurement, a reading at two nominal supply voltages (3.3 and 5V) is
RMS
/100 Hz) signal is introduced onto the supply
AC
measurement, a reading at two
SS
which represents the
STPM11/12/13/14
OUT
. This