AD10465 datasheet(13/25 Pages) AD

13 / 25 page

AD10465

Data Sheet

Rev. B | Page 12 of 24

THEORY OF OPERATION

The AD10465 is a high dynamic range, 14-bit, 65 MHz pipeline

delay (three pipelines) analog-to-digital converter. The custom

analog input section maintains the same input ranges (1 V p-p,

2 V p-p, and 4 V p-p) and input impedance (100 Ω, 200 Ω, and

400 Ω) as the AD10242.

The AD10465 employs four monolithic Analog Devices

components per channel (AD8037, AD8138, AD8031, and

AD6644), along with multiple passive resistor networks and

decoupling capacitors to fully integrate a complete 14-bit

analog-to-digital converter.

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, ±1.0 V, or ±2.0 V by choosing

the proper input terminal for the application.

The AD10465 analog input includes an AD8037 amplifier

featuring 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 configuration. 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 AD6644, maximizing the performance of the ADC.

The AD8031 provides the buffer for the internal reference of the

AD6644. The internal reference voltage of the AD6644 is

designed to track the offsets and drifts of the ADC 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. The AD6644 reference

voltage sets the output common mode on the AD8138 at 2.4 V,

which is the midsupply level for the AD6644.

The AD6644 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° 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, TH1. The high state of the ENCODE pulse places

TH1 in hold mode. The held value of TH1 is applied to the

input of a 5-bit coarse ADC1. The digital output of ADC1

drives 14 bits of precision, which is achieved through laser

trimming. The output of DAC1 is subtracted from the delayed

analog signal at the input of TH3 to generate a first residue

signal. TH2 provides an analog pipeline delay to compensate for

the digital delay of ADC1.

The first residue signal is applied to a second conversion stage

consisting of a 5-bit ADC2, 5-bit DAC2, and pipeline TH4. The

second DAC requires 10 bits of precision, which is met by the

process with no trim. The input to TH5 is a second residue

signal generated by subtracting the quantized output of DAC2

from the first residue signal held by TH4. TH5 drives a final

6-bit ADC3.

The digital outputs from ADC1, ADC2, and ADC3 are added

together and corrected in the digital error correction logic to

generate the final output data. The result is a 14-bit parallel

digital CMOS-compatible word, coded as twos complement.

USING THE FLEXIBLE INPUT

The AD10465 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. While the standard inputs are ±0.5 V, ±1.0 V,

and ±2.0 V, the user can select the input impedance of the

AD10465 on any input by using the other inputs as alternate

locations for GND or an external resistor. Table 5 summarizes

the impedance options available at each input location.

Table 5. Input Impedance Options

Input

Impedance

Condition

AIN1

100 Ω

When AIN2 and AIN3 are open

75 Ω

When AIN3 is shorted to GND

50 Ω

When AIN2 is shorted to GND

AIN2

200 Ω

When AIN3 is open

100 Ω

When AIN3 is shorted to GND

75 Ω

When AIN2 to AIN3 has an external resistor of 300 Ω, with AIN3 shorted to GND

50 Ω

When AIN2 to AIN3 has an external resistor of 100 Ω, with AIN3 shorted to GND

AIN3

400 Ω

100 Ω

When AIN3 has an external resistor of 133 Ω to GND

75 Ω

When AIN3 has an external resistor of 92 Ω to GND

50 Ω

When AIN3 has an external resistor of 57 Ω to GND

AD10465 Datasheet(PDF) 13 Page - Analog Devices

AD10465 Datasheet(HTML) 13 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Datasheet Download

Link URL