REF5045 datasheet(37/62 Pages) TI2

37 / 62 page

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ADS8881

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SBAS547D – MAY 2013 – REVISED AUGUST 2015

Product Folder Links: ADS8881

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Typical Applications (continued)

The reference buffer is designed with the THS4281 and OPA333 in a composite architecture to achieve superior

dc and ac performance at a reduced power consumption, compared to using a single high-performance amplifier.

The THS4281 is a high-bandwidth amplifier with a very low output impedance of 1 Ω at a frequency of 1 MHz.

The low output impedance makes the THS4281 a good choice for driving a high capacitive load to regulate the

voltage at the reference input of the ADC. The high offset and drift specifications of the THS4281 are corrected

by using a dc-correcting amplifier (OPA333) inside the feedback loop. The composite scheme inherits the

extremely low offset and temperature drift specifications of the OPA333.

For the input driving amplifiers, key specifications include rail-to-rail input and output swing, high bandwidth, high

slew rate, and fast settling time. The OPA350 CMOS amplifier meets all these specification requirements for this

circuit with a single-supply and low quiescent current. The component values of the antialiasing filter are selected

to meet the settling requirements of the system as well as to maintain the stability of the input driving amplifiers.

11.2.1.3 Application Curve

18-bit INL

Figure 66. Limited Point Linearity

For step-by-step design procedure, circuit schematics, bill of materials, PCB files, simulation results, and test

results, see 18-Bit Data Acquisition (DAQ) Block Optimized for 1-μs Full-Scale Step Response (TIDU012).

REF5045 Datasheet(PDF) 37 Page - Texas Instruments