Datasheet AD8651, AD8652 (Analog Devices) - 17

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Data Sheet AD8651/AD8652 5V +3.5V + 10kΩ U1 3 V AD865x OUT + V+ 33Ω VCC – 600Ω 47pF 10kΩ AD865x IN 1µF AD7685 2 V– VIN – 2.7nF 2V p-p –1.5V
058
1kΩ VIN
03301-
0V TO 5V f
060 Figure 59. THD + N Test Circuit
IN = 45kHz 1kΩ
03301-
Driving a 16-Bit ADC
Figure 61. AD865x Driving a 16-Bit ADC The AD865x family is an excellent choice for driving high speed, high precision ADCs. The driver amplifier for this type
Table 6. Data Acquisition Solution of Figure 60
of application needs low THD + N as well as quick settling time.
Parameter Reading (dB)
Figure 61 shows a complete single-supply data acquisition THD + N 105.2 solution. The AD865x family drives the AD7685, a 250 kSPS, SFDR 106.6 16-bit data converter.1 2nd Harmonics 107.7 3rd Harmonics 113.6 The AD865x is configured in an inverting gain of 1 with a 5 V single supply. Input of 45 kHz is applied, and the ADC samples at 250 kSPS. The results of this solution are listed in Table 6. The advantage of this circuit is that the amplifier and ADC can be powered with the same power supply. For the case of a noninverting gain of 1, the input common-mode voltage encompasses both supplies. 1 For more information about the AD7685 data converter, go to http://www.analog.com/Analog_Root/productPage/productHome/0%2C21 21%2CAD7685%2C00.html
0 fSAMPLE = 250kSPS fIN = 45kHz –20 INPUT RANGE = 0V TO 5V ) le –40 a c –60 Full S of –80 dB ( E D –100 LITU P –120 M A –140 –160 0 10 20 30 40 50 60 70 80 90 100 110 120
059
FREQUENCY (kHz)
03301- Figure 60. Frequency Response of AD865x Driving a 16-Bit ADC Rev. D | Page 17 of 20 Document Outline Features Applications Pin Configurations General Description Table of Contents Revision History Specifications Electrical Characteristics Absolute Maximum Ratings ESD Caution Thermal Resistance Typical Performance Characteristics Applications Theory of Operation Rail-to-Rail Output Stage Rail-to-Rail Input Stage Input Protection Overdrive Recovery Layout, Grounding, and Bypassing Considerations Power Supply Bypassing Grounding Leakage Currents Input Capacitance Output Capacitance Settling Time THD Readings vs. Common-Mode Voltage Driving a 16-Bit ADC Outline Dimensions Ordering Guide