Precision, Selectable Gain,
Fully Differential Funnel Amplifier
AD8475
FUNCTIONAL BLOCK DIAGRAMS
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
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 converter up to 4 MSPS
10 nV/√Hz output noise
1kΩ
+IN 0.4x
+IN 0.8x
–IN 0.8x
–IN 0.4x
1
2
3
4
12 NC
1.25kΩ
1.25kΩ
1.25kΩ
1.25kΩ
11 –OUT
10 +OUT
AD8475
1kΩ
9
VOCM
3 ppm/°C gain drift
500 μV maximum output offset
50 V/μs slew rate
NC = NO CONNECT
Low power: 3.2 mA supply current
Figure 1. 16-Lead LFCSP
APPLICATIONS
ADC drivers
Differential instrumentation amplifier building blocks
Single-ended-to-differential converters
1kΩ
1.25kΩ
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.
1.25kΩ
AD8475
1.25kΩ
1kΩ
1.25kΩ
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).
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.
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.
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 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.
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.
Rev. B
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