Ultrasonic Flow Converters

AS6040 Ultrasonic Flow Converter

UFC Solution for Gas & Water Meters

AS6040 ultrasonic flow converter ICThe AS6040 system is made of four major blocks: supervisor, frontend, post processing and interface. The supervisor manages all tasks and is the master of the whole system, making the AS6040 autonomous.The frontend integrates a high-voltage driver, an integrated PGA and an offset-stabilized comparator in the receive path, a precision TDC for the time-of-flight measurement, amplitude measurement as well as an RDC unit for temperature measurement. In flow meter mode, the 32-bit CPU in combination with 4k of ROM code and 4k of NVRAM does the post processing for flow calculation. In time conversion mode the CPU is not active and the chip sends the raw time-of-flight data. It communicates to an external microcontroller via SPI interface. By means of the integrated pulse interface the AS6040 can run also in stand-alone mode.

The analog front-end is supported by an integrated charge pump to provide a programmable fire voltage in the range from 6 V o 17 V with a frequency from 50 kHz up to 1 MHz. The integrated PGA gain factor can be adjusted from 2 to 250. The first hit level detection starts with a programmable offset up to 220mV. After this is set down to 0 mV, the AS6040 can measure up to 31 zero crossings within a single receive burst. The front end achieves in single shot less than 300 ps rms noise single shot with good 500kHz transducers. The first-hit pulse width information and the amplitude can be used to regulate the first hit level, but also to get information about situations with bubbles or empty tubes. It comes in a compact QFN48 package and allows compact designs thanks to a small number of external components.

Ultrasonic Flow Converters (UFC)


  • High performance + ultra-low power 32-Bit CPU with:
  • 120 * 32 NVRAM (non-volatile RAM) for user firmware parameter & data
  • 3968 * 8 bit NVRAM (non-volatile RAM) for user firmware program code
  • 4k * 8 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 frontend with < 50 ps single shot
  • Ultra low power consumption
  • SPI serial interface


  • Single-chip solution provides ready flow information
  • System design compatible with meachanical 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


Analog Frontend
Yes, with PGA and HV charge pump
First Wave Detection
Yes, Split burst
Amplitude Measurement
Number of Hits
Resolution TDC [ps]
Operating Supply Range
3.0 to 3.6
SPI, Pulse, 2-wire master
4k NVRAM, 4k ROM
Ambient Temperature Range [°C]
-40 to +85


  • Residential Gas Meters
  • Industrial Gas Meters
  • Clamp-on Water Meters
  • Volume Counters
Block Diagram of the AS6040 Ultrasonic Flow Converter for gas and water meters

Ordering Numbers

Type Part number Package RoHS compl. Shipping package
TDC-GP22 MNR 1949 QFN32 Yes Tray
TDC-GP22 MNR 1950 QFN32 Yes Tape & Reel (5k)
GP22-EVA-KIT MNR 1951 System Yes Box
GP22-DEMO-KIT MNR 1979 System Yes Box
TDC-GP21 MNR 1839 QFN32 Yes Tray
TDC-GP21 MNR 1720 QFN32 Yes Tape & Reel (3K/5K)
GP21-EVA-KIT MNR 1781 System Yes Box
TDC-GP2 MNR 1058 QFN32 Yes Tray
TDC-GP2 MNR 1480 QFN32 Yes Tape & Reel (2k)
TDC-GP1 MNR 278 TQFP44 Yes Tray
TDC-GPX MNR 975 TQFP100 Yes Tray
TDC-GPX-FG MNR 1089 TFBGA120 Yes Tray