UM0402 datasheet(4/35 Pages) STMICROELECTRONICS

4 / 35 page

Overview

UM0402

4/35

Overview

1.1

Safety rules

This board can be connected to mains voltage (220V). In the case of improper use, wrong

installation or malfunction, there is a danger of serious personal injury and damage to

property. All operations such as transport, installation and commissioning as well as

maintenance should be carried out only by skilled technical personnel (regional accident

prevention rules must be observed).

Danger:

Due to the risk of death when using this prototype on mains

voltage (220V), only skilled technical personnel who are

familiar with the installation, mounting, commissioning and

operation of power electronic systems and have the

qualifications needed to perform these functions, may use

this prototype.

1.2

Conventions

The lowest analog and digital power supply voltage is called VSS. All voltage specifications

for digital input/output pins are referred to as VSS. The highest OTP writing power supply

voltage is VOTP. The highest power supply voltage of the device is VCC.

Positive currents flow into a pin. Sinking means that the current flows to the pin while

sourcing means that the current flows from the pin.

Timing specifications of signals treated by the device are relative to the CLKOUT. This signal

is fed from a 4.194 MHz on-board crystal oscillator.

Timing specifications of SPI interface signals are relative to the SCLNLC, which need not to

be in phase with CLKOUT.

A positive logic convention is used in all equations.

1.3

Multi tariff meter description

The single-phase multi-tariff energy meter reference board is designed using STPM14

metering ASSP and ST72F321BR6 microcontroller.

The STPM14 belongs to STPM1x metering devices family. It measures the active energy

that is output as a pulse train with a frequency proportional to the measured power. It

supports tamper detection, monitoring both phase and neutral line wires, where two current

transformers are used as current sensors. The clock to STPM14 is supplied by a crystal of

frequency 4.194304 MHz.

The microcontroller drives the LCD, processes measurements coming from the ASSP and

manages RTC and EEPROM functionalities, for example saving relevant data in EEPROM

before moving to halt mode during power down. It also manages maximum demand

calculation on a daily, monthly or three-month base.

UM0402 Datasheet(PDF) 4 Page - STMicroelectronics

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