DAC8801

+

±

I

OUT

R

FB

V

REF

V

DD

+6V

-6V

OP Ax863

V

OU T

TR

X1

+

±

OP Ax863

12 V

R

ISO

+

±

R

F

R

G

C

G

C

Filt

C

AC2

R¶

R¶

3.3 V

PGA

ADC

MSP430FR6043

OP Ax863

TR

X2

Processor

Transmitter

Receiver

Receiver

Transmitter

NODE-1

NODE-2

3.3 V

12 V

0 V

12 V

V

TX

0 V

12 V

V

TX

V

R X

V

R X

t

12

t

21

R

R

C

AC1

12 V

17

OPA2863

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SBOS982A – JUNE 2020 – REVISED JUNE 2020

Product Folder Links: OPA2863

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Copyright © 2020, Texas Instruments Incorporated

9.6 Clamp-On Ultrasonic Flow Meter

changes with and used to determine the flow rate. Figure 17 shows a representative schematic for a non-

intrusive ultrasonic flow meter using the OPAx863 devices and 12-V transducer excitation. For the forward path,

the OPAx863 devices are used as a unity-gain buffer for 12-V pulsed transducer excitation at Node 1. At the

same time, the receiver circuit at Node 2, also using the OPAx863 devices, first provides an AC-gain followed by

a DC-level shift to lead to the PGA, ADC and processing within the MSP430 microcontroller.

For the reverse path, Node 2 and Node 1 use similar transmit and receive circuits discussed above. The

OPAx863 devices wide GBW of 50 MHz introduces minimal phase-delay and low-noise for superior flow rate

measurement. In battery powered systems, the amplifier stays in power-down mode for a majority of the time,

resulting in very small average system-level power consumption and prolonged battery lifetime with its 1.5 µA

(maximum) power-down mode quiescent current. Since the transmit and receive signal chains are connected to

the same point at the respective node transducers, the OPAx863 devices 12.6-V supply voltage capability

enables 12-V transducer excitation capability with damage to the front-end and need for external switches to

make a compact solution. This makes the OPAx863 devices suitable for flow measurements in large diameter

pipes and non-intrusive flow meters.

Figure 17. Non-Intrusive Ultrasonic Flow Meter

9.7 Variable Reference Generator Using MDAC

High-speed amplifiers may be used as a voltage buffer at MDAC output to generate a fast settling variable

reference voltage. Figure 18 shows a representative circuit using DAC8801 and OPAx863.

Figure 18. Variable Reference Generator Using MDAC and OPAx863