Low-power fully-testable flow meter in CMOS ASIC

This paper shows a circuit designed to measure the water flow in private homes and industrial buildings. The circuit was developed with hard constraints in size and in power consumption. It counts pulses coming from a sensor (multipole turbine placed inside the water pipe) operating as a slave of a microprocessor. It measures the period of that signal using an exponential counter (counting integer part and mantissa) to prevent overflows extending the dynamic range. The data is sent to the microprocessor through a bi-directional serial channel, using a protocol similar to the I²C standard. The circuit has interrupt generation capabilities. Since it has to be used with a wide range of sensors and in different operating modes, it can be programmed from the microprocessor via command and status registers. It has an adaptive clock to minimize power dissipation when water flow is zero or with small water leaks. Since the circuit will be manufactured in large quantities additional circuitry was added for testing purposes