AD8476ARMZ-RL

ALLGEMEINE BESCHREIBUNG

The AD8476 is a very low power, fully differential precision amplifier with integrated gain resistors for unity gain. It is an ideal choice for driving low power, high performance ADCs as a

single-ended-to-differential or differential-to-differential amplifier. It provides a precision gain of 1, common-mode level shifting, low temperature drift, and rail-to-rail outputs for maximum dynamic range.

Der AD8476 bietet außerdem einen Überspannungsschutz für große industrielle Eingangsspannungen bis zu ±23 V, während er mit einer doppelten 5-V-Versorgung arbeitet. Die Verlustleistung bei einer einzelnen 5-V-Versorgung beträgt nur 1,5 mW.

The AD8476 works 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 on the market, the AD8476 is  a high precision amplifier. With 200 µV maximum output offset, 39 nV/√Hz noise, and −102 dB THD + N at 10 kHz, the AD8476 pairs well with low power, high accuracy converters.  Considering its low power consumption and high precision, the slew-enhanced AD8476 has excellent speed, settling to 16-bit

Präzision für 250 kSPS Erfassungszeiten. Der AD8476 ist in platzsparenden 16-poligen, 3 mm × 3 mm großen LFCSP- und 8-poligen MSOP-Gehäusen erhältlich. Er ist über den gesamten Temperaturbereich von -40°C bis +125°C spezifiziert.

FEATURES

Sehr geringe Leistung

330 μA Versorgungsstrom

Äußerst geringe harmonische Verzerrung

-126 HD2 bei 10 kHz

-128 HD3 bei 10 kHz

Vollständig differentielle oder Single-Ended-Eingänge/Ausgänge

Differentialausgang zur Ansteuerung von Präzisions-ADCs

Steuert geschaltete Kondensatoren und Σ-Δ ADCs

Rail-to-Rail-Ausgänge

VOCM-Pin stellt den Gleichtakt des Ausgangs ein

Robuste Überspannung bis zu 18 V über die Versorgung hinaus

Hohe Leistung

Geeignet für die Ansteuerung von 16-Bit-Wandlern mit bis zu 250 kSPS

39 nV/√Hz Ausgangsrauschen

1 ppm/°C Verstärkungsdrift maximal

200 μV maximaler Ausgangsoffset

10 V/μs Anstiegsrate

6 MHz Bandbreite

Einfache Versorgung: 3 V bis 18 V

Doppelte Versorgung: ±1,5 V bis ±9 V

ANWENDUNGEN

ADC-Treiber

Differenzieller Instrumentenverstärker Baustein

Single-Ended-zu-Differential-Wandler

Batteriebetriebene Instrumente

ANWENDUNGSINFORMATIONEN

TYPISCHE KONFIGURATION

The AD8476 is designed to facilitate single-ended-to-differential conversion, common-mode level shifting, and precision processing of signals so that they are compatible with low voltage ADCs. Figure 54 shows a typical connection diagram of the AD8476. SINGLE-ENDED-TO-DIFFERENTIAL CONVERSION Many industrial systems have single-ended inputs from input

sensors; however, the signals are frequently processed by high performance differential input ADCs for higher precision. The AD8476 performs the critical function of precisely converting single-ended signals to the differential inputs of precision ADCs, and it does so with no need for external components.  To convert a single-ended signal to a differential signal, connect one input to the signal source and the other input to ground (see Figure 54). Note that either input can be driven by the source with the only effect being that the outputs have reversed polarity. The AD8476 also accepts truly differential input signals in

precision systems with differential signal paths.

EINSTELLUNG DER AUSGANGS-GLEICHTAKTSPANNUNG

The VOCM pin of the AD8476 is internally biased by a precision voltage divider comprising of two 1 MΩ resistors between the supplies. This divider level shifts the output to midsupply. Relying on the internal bias results in an output common-mode voltage that is within 0.05% of the expected value.  In cases where control of the output common-mode level is desired, an external source or resistor divider can be used to drive the VOCM pin. If driven directly from a source, or with a resistor divider of unequal resistor values, the resistance seen by the VOCM pin should be less than 1 kΩ. If an external voltage divider consisting of equal resistor values is used to set VOCM to midsupply, higher values can be used because the external resistors are placed in parallel with theinternal resistors. The output common-mode offset listed in the Specifications section assumes that the VOCM input is driven by a low impedance voltage source.  Because of the internal divider, the VOCM pin sources and sinks current, depending on the externally applied voltage and its associated source resistance. It is also possible to connect the VOCM input to the commonmode level output of an ADC; however, care must be taken to ensure that the output has sufficient drive capability. The input impedance of the VOCM pin is 500 kΩ. If multiple AD8476

devices share one ADC reference output, a buffer may be neces

sary to drive the parallel inputs.