AS6040 Ultrasonic Flow Converter

AS6040 Ultrasonic Flow Converter

AS6040 is an ultrasonic flow converter (UFC) solution dedicated to gas meters, but suitable for water meters, too.

It is made up of four main parts: the supervisor, the front end, the post-processing unit, and the interface. The supervisor is the master of the system and controls all of the other parts, making the AS6040 autonomous. 

The front end has a high-voltage driver, an integrated PGA, an offset-stabilized comparator in the receive path, a precision TDC for the time-of-flight measurement, amplitude measurement, and an RDC unit for temperature measurement. 

In flow meter mode, the 32-bit CPU and the post-processing unit calculate the flow. In time conversion mode, the CPU is inactive, and the chip sends the raw time-of-flight data. 

The AS6040 communicates with an external microcontroller via SPI interface. It can also run in stand-alone mode using the integrated pulse interface.

AS6040 Ultrasonic Flow Converter

AS6040 features and benefits


  • High performance + ultra-low power 32-Bit CPU
  • 120 * 32 bit NVRAM (non-volatile RAM) for user firmware parameter & data
  • 3968 * 8 bit NVRAM (non-volatile RAM) for user firmware program code
  • 4k * 8 bit ROM for system task code and special flow library code
  • 50 kHz to 1 MHz at 6 V to 17 V drive voltage, generated from battery supply
  • Integrated PGA, gain 2 to 200
  • First hit level and phase detection
  • Amplitude measurement
  • Up to 31 zero crossing measurements
  • Precision time-to-digital converter and low-noise front-end with < 50 ps single shot with good 1MHz transducers on a DN20
  • Ultra-low power consumption
  • SPI serial interface


  • Single-chip solution provides ready flow information
  • System design compatible with mechanical meters
  • High flexibility in choice for external µP handling communication and further data management
  • Operation from Battery
  • Precision down to low flow rates
  • Leakage detection
  • Handles weak signals for small transducers and multiple reflections
  • Compact design
  • Low BOM

Product properties

  • Analog Frontend Yes, with PGA and HV charge pump
  • First Wave Detection Yes, split burst
  • Amplitude Measurement Yes
  • Number of hits 31
  • Resolution TDC [ps] 22
  • Operating Supply Range 3.0 to 3.6
  • Interface SPI, Pulse, 2-wire master
  • CPU 32-bit
  • Firmware -
  • Memory 4k NVRAM, 4k ROM
  • GPIO 5
  • Ambient Temperature Range [°C] -40 to +85
  • Package QFN48


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Development kit

The AS6040 development kit allows customers a quick and intuitive approach to using the AS6040 UFC in ultrasonic flow meter applications.