AD8475_16 Datasheet, PDF (1/25 Pages) Analog Devices – Precision, Selectable Gain, Fully Differential Funnel Amplifier

Data Sheet
Precision, Selectable Gain,
Fully Differential Funnel Amplifier
AD8475
FEATURES
Precision attenuation: G = 0.4, G = 0.8
Fully differential or single-ended input/output
Differential output designed to drive precision ADCs
Drives switched capacitor and Σ-Δ ADCs
Rail-to-rail output
VOCM pin adjusts output common-mode voltage
Robust overvoltage protection up to ±15 V (VS = +5 V)
Single supply: 3 V to 10 V
Dual supplies: ±1.5 V to ±5 V
High performance
Suited for driving 18-bit converters up to 4 MSPS
10 nV/√Hz output noise
3 ppm/°C gain drift
500 μV maximum output offset
50 V/μs slew rate
Low power: 3.2 mA supply current
APPLICATIONS
ADC drivers
Differential instrumentation amplifier building blocks
Single-ended-to-differential converters
GENERAL DESCRIPTION
The AD8475 is a fully differential, attenuating amplifier with
integrated precision gain resistors. It provides precision attenuation
(by 0.4 or 0.8), common-mode level shifting, and single-ended-to-
differential conversion along with input overvoltage protection.
Power dissipation on a single 5 V supply is only 16 mW.
The AD8475 is a simple to use, fully integrated precision gain
block, designed to process signal levels of up to ±10 V on a single
supply. It provides a complete interface to make industrial level
signals directly compatible with the differential input ranges of low
voltage high performance 16-bit or 18-bit single-supply successive
approximation (SAR) analog-to-digital converters (ADCs).
The AD8475 comes with two standard pin-selectable gain
options: 0.4 and 0.8. The gain of the part is set by driving the
input pin corresponding to the appropriate gain.
The AD8475 also provides overvoltage protection from large
industrial input voltages up to ±15 V while operating on a single
5 V supply. The VOCM pin adjusts the output voltage common
mode for precision level shifting, to match the ADC’s input range
and maximize dynamic range.
Rev. C
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FUNCTIONAL BLOCK DIAGRAMS
+IN 0.4x 1
+IN 0.8x 2
–IN 0.8x 3
–IN 0.4x 4
1.25kΩ
1.25kΩ
1.25kΩ
1.25kΩ
1kΩ
AD8475
1kΩ
12 NC
11 –OUT
10 +OUT
9 VOCM
NC = NO CONNECT
Figure 1. 16-Lead LFCSP
1kΩ
1.25kΩ
1.25kΩ
1.25kΩ
1.25kΩ
AD8475
1kΩ
NC = NO CONNECT
Figure 2. 10-Lead MSOP
The AD8475 works extremely well with SAR, Σ-Δ, and pipeline
converters. The high current output stage of the part allows it to
drive the switched capacitor front-end circuits of many ADCs with
minimal error.
Unlike many differential drivers in the market, the AD8475 is a
high precision amplifier. With 500 µV maximum output offset,
10 nV/√Hz output noise, and −112 dB THD + N, the AD8475
pairs well with high accuracy converters. Considering its low power
consumption and high precision, the slew-enhanced AD8475 has
excellent speed, settling to 18-bit precision for 4 MSPS acquisition.
The AD8475 is available in a space-saving 16-lead 3 mm × 3 mm
LFCSP package and a 10-lead MSOP package. It is fully specified
over the −40°C to +85°C temperature range.
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