STPM01_11 STMICROELECTRONICS [STMicroelectronics], STPM01_11 Datasheet - Page 17

• Manufacturer Part Number: STPM01_11
• Description: Programmable single phase energy metering IC with tamper detection
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

STPM01
8
8.1
8.2
Theory of operation
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
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
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
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.
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.
Table 16
for configuration register). Using these bits the STPM01 can be
Doc ID 10853 Rev 8
Table
5) are used to provide information on tamper, no
Table
5), while the SPI pins are used to
Theory of operation
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