OPA863DBVR datasheet(27/52 Pages) TI

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9.2.4 Variable Reference Generator Using MDAC

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

reference voltage. Figure 9-5 shows a representative circuit using DAC8801 and OPAx863.

DAC8801

–

OUT

REF

+6 V

6 V

OPAx863

OUT

Figure 9-5. Variable Reference Generator Using MDAC and OPAx863

9.2.5 Clamp-On Ultrasonic Flow Meter

Figure 9-6 shows how ultrasonic flow meters measure the rate of flow of a liquid using transit-time difference

(t12–t21), which depends on the flow rate. Figure 9-6 shows a representative schematic for a non-intrusive

ultrasonic flow meter using the OPAx863 and 12-V transducer excitation. The OPAx863 are used for the forward

path as a unity-gain buffer for 12-V pulsed transducer excitation at NODE 1. At the same time, the receiver

circuit at NODE 2 (which also uses the OPAx863) first provides an ac-gain followed by a dc-level shift to lead to

the PGA, ADC, and processor within the MSP430™ microcontroller.

NODE 2 and NODE 1 use similar transmit and receive circuits (discussed previously) for the reverse path.

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

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

This configuration results in very small average system-level power consumption and prolonged battery lifetime

with the 1.5

‑µA (maximum) power-down mode quiescent current with a 3-V supply. The transmit and receive

signal chains are connected to the same point at the respective node transducers. Therefore, the OPAx863

12.6-V supply voltage capability enables 12-V transducer excitation without any damage to the front-end, or a

need for external switches, thus enabling a more compact solution. These specifications make the OPAx863 an

excellent choice for flow measurements in large diameter pipes and non-intrusive flow meters. The TIDM-02003

reference design discusses an ultrasonic gas flow sensing subsystem which uses high-speed amplifiers for

front-end amplification.

OP Ax863

12 V

ISO

Filt

AC2

R¶

3.3 V

PGA

ADC

MSP430FR6043

OP Ax863

Processor

Transmitter

Receiver

Transmitter

NODE-1

NODE-2

3.3 V

12 V

0 V

12 V

0 V

12 V

R X

AC1

12 V

Figure 9-6. Non-Intrusive Ultrasonic Flow Meter

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OPA863, OPA2863, OPA4863

SBOS982J – JUNE 2020 – REVISED JUNE 2023

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