STPMC1 datasheet(19/77 Pages) STMICROELECTRONICS

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STPMC1

Theory of operation

Doc ID 15728 Rev 6

19/77

Theory of operation

9.1

General operation

The STPMC1 (also called a calculator) is an ASSP designed for effective measurement in

power line systems utilizing the Rogowski coil, current transformer, Shunt or Hall current

sensors. This device, used with the STMicroelectronics STPMSx companion chip (an

analog front-end device), can be implemented as standalone or as a peripheral in a

microprocessor based 1-, 2- or 3-phase energy meter.

The calculator consists of three sections: analog, digital and OTP (see

Figure 1):

●

The analog section is composed of a band-gap voltage reference and a low-drop

voltage regulator.

●

The digital section consists of a system control, clock generator, three PDSP and a

NDSP, a SPI interface.

●

The 112-bit OTP block and the 16 system signals, used for testing, configuration and

calibration purposes, are controlled through SPI by means of a dedicated command

set.

The calculator has five input data pins, of which four are fed by signals generated by the

STPMSx, see

Table 9.

Three of them (DAR/DAS/DAT) are used to receive multiplexed signals of voltage and

current, implementing energy measurement in 1-, 2- and 3-phase (3 and 4 wires) systems.

After being de-multiplexed, each phase input is sent to the correspondent DSP unit that

processes voltage and current information and performs energy calculation, according to

the settings of the configuration bits (see

Table 33).

The DAN input, which also receives a multiplexed signal output from STPMSx device, is

typically used to monitor neutral current for anti tampering functions in 1-, 2- and 3-phase (4

wires) systems. Normally the STPMSx monitors current and voltage but in case of neutral

monitoring the voltage channel can be connected to a different type of sensor, for example a

temperature sensor.

The fifth input data pin (DAH) accepts non-multiplexed

ΔΣ signals. It can be used for EMI

sensing through Hall sensors or for temperature sensing.

The companion chip (STPMSx) embeds 2

ΔΣ ADC converters and the necessary logic

capable of providing the multiplexed

ΔΣ streams.

See the STPMSx documentation for more details.

Table 9.

Input channels from the STPMSx

Channel name

Property

Signal 1

Signal 2

DAR

Multiplexed

Voltage

Current

DAS

Multiplexed

Voltage

Current

DAT

Multiplexed

Voltage

Current

DAN

Multiplexed

Temperature

Current

DAH

Not multiplexed

EMI or temperature

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