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Overview
In addition to measuring the actual amount of gas used, a gas meter must also be capable of detecting abnormal conditions and to shut off the gas supply to prevent gas leaks. MCUs used in a gas meter designs must incorporate functionality for connecting to a variety of sensors, with low power consumption and high reliability, as the meters are constantly in operation. Regulatory bodies the world over require that gas meters are replaced every 10 years, so as a minimum, their battery life must be sufficient for this length of time. This requires MCUs used in gas meters to have extremely low current consumption.
Renesas’ R8C/Lx Series and µPD780958 of MCUs operate while consuming very little power. They also incorporate a highly reliable watchdog timer (WDT) and an on-chip oscillator circuits with minimal susceptibility to oscillation errors, in order to increase the fail-safe functionality of the MCU. These MCUs are suitable for the development of gas meters demanding stable operation with a high level of reliability.
System Block Diagram
Recommended Products
| Block | Semiconductor device | Recommended products | Features, etc. |
|---|---|---|---|
| Main controller | MCU | 78K0/Lx3 | On-chip LCD driver, low power consumption |
| R8C/Lx Series | |||
| UPD780958 | 8-bit MASK ROM MCU, for Gas Meters | ||
| EEPROM | R1EX24xxx Series | I2C bus interface *1 | |
| R1EX25xxx Series | SPI bus interface *2 | ||
| MCU peripheral | Reset IC | RNA519xx Series | Variable detection voltage |
| General use surge absorption circuit protection, etc. | Zener diode | HZMxNB Series | 3-terminal (1 device included) face-mount outline |
| HZU/HZC Series | 2-terminal face-mount outline | ||
| NNCDxxDA Series | High ESD tolerance optimal for use in surge absorption | ||
| RDxxS Series | 2-terminal face-mount outline | ||
| Switching diode | HSM2838C, HSM123 | 3-terminal (2 devices included) face-mount outline | |
| HSU119/HSC119 | 2-terminal face-mount outline | ||
| Schottky diode | HRB0502A | 3-terminal face-mount outline (low VF) | |
| HRC0103C | 2-terminal face-mount outline (low VF, low leak current) | ||
| RKR0202AQE | 3-terminal face-mount outline (low VF) | ||
| I/O section | MOS FET | HAT1094C, HAT1095C | Low voltage (1.8 V) drive, CMFPAK-6 |
| HAT2205C, HAT2206C | Low voltage (1.8 V) drive, CMFPAK-6 | ||
| RQJ0203WGDQA, RQJ0202VGDQA | Low voltage (2.5 V) drive, MPAK | ||
| RQK0203SGDQA, RQK0204TGDQA | Low voltage (2.5 V) drive, MPAK | ||
| µPA1917, µPA1919 | Low voltage (1.8 V) drive, SC-95 |
*1 I2C: Inter-Integrated Circuit
*2 SPI: Serial Peripheral Interface
Related Application Notes/Sample Code
|
Title
| Document No. |
|---|---|
| Power MOS FET application note | REJ05G0001-0200 |
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