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AD13280 Fiches technique(PDF) 9 Page - Analog Devices |
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AD13280 Fiches technique(HTML) 9 Page - Analog Devices |
9 / 20 page REV. 0 AD13280 –9– AMP-IN-X-1 100 100 TO AD8037 AMP-IN-X-2 Figure 2. Single-Ended Input Stage LOADS LOADS ENCODE 10k 10k ENCODE AVCC AVCC 10k 10k AVCC AVCC Figure 3. ENCODE Inputs CURRENT MIRROR CURRENT MIRROR DR OUT DVCC VREF DVCC Figure 4. Digital Output Stage CURRENT MIRROR CURRENT MIRROR D0–D11 100 DVCC VREF DVCC Figure 5. Digital Output Stage THEORY OF OPERATION The AD13280 is a high-dynamic range 12-bit, 80 MHz pipeline delay (three pipelines) analog-to-digital converter. The custom analog input section provides input ranges of 1 V and 2 V p-p and input impedance configurations of 50 Ω, 100 Ω, and 200 Ω. The AD13280 employs four monolithic ADI components per channel (AD8037, AD8138, AD8031, and a custom ADC IC), along with multiple passive resistor networks and decoupling capacitors to fully integrate a complete 12-bit analog-to-digital converter. In the single-ended input configuration the input signal is passed through a precision laser trimmed resistor divider allowing the user to externally select operation with a full-scale signal of ±0.5 V, or ±1.0 V by choosing the proper input terminal for the application. The result of the resistor divider is to apply a full- scale input approximately 0.4 V to the noninverting input of the internal AD8037 amplifier. The AD13280 analog input includes an AD8037 amplifier featur- ing an innovative architecture that maximizes the dynamic range capability on the amplifiers’ inputs and outputs. The AD8037 amplifier provides a high input impedance and gain for driving the AD8138 in a single-ended to differential amplifier configura- tion. The AD8138 has a –3 dB bandwidth at 300 MHz and delivers a differential signal with the lowest harmonic distortion available in a differential amplifier. The AD8138 differential outputs help balance the differential inputs to the custom ADC maximizing the performance of the device. The AD8031 provides the buffer for the internal reference analog- to-digital converter. The internal reference voltage of the custom ADC is designed to track the offsets and drifts and is used to ensure matching over an extended temperature range of operation. The reference voltage is connected to the output common-mode input on the AD8138. This reference voltage sets the output common mode on the AD8138 at 2.4 V, which is the midsupply level for the ADC. The custom ADC has complementary analog input pins, AIN and AIN. Each analog input is centered at 2.4 V and should swing ±0.55 V around this reference. Since AIN and AIN are 180 degrees out of phase, the differential analog input signal is 2.2 V peak-to-peak. Both analog inputs are buffered prior to the first track-and-hold. The custom ADC digital outputs drive 100 Ω series resistors (Fig- ure 5). The result is a 12-bit parallel digital CMOS-compatible word, coded as two’s complement. USING THE SINGLE-ENDED INPUT The AD13280 has been designed with the user’s ease of opera- tion in mind. Multiple input configurations have been included on-board to allow the user a choice of input signal levels and input impedance. The standard inputs are ± 0.5 V and 1.0 V. The user can select the input impedance of the AD13280 on any input by using the other inputs as alternate locations for the GND. The following chart summarizes the impedance options available at each input location. AMP-IN-X-1 = 100 Ω when AMP-IN-X-2 is open. AMP-IN-X-1 = 50 Ω when AMP-IN-X-2 is shorted to GND. AMP-IN-X-2 = 200 Ω when AMP-IN-X-1 is open. Each channel has two analog inputs AMP-IN-A-1 and AMP- IN-A-2 or AMP-IN-B-1 and AMP-IN-B-2. Use AMP-IN-A-1 |
Numéro de pièce similaire - AD13280 |
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Description similaire - AD13280 |
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