ADC12DC080 datasheet(16/27 Pages) TI1

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ADC12DC080

SNAS405B – SEPTEMBER 2007 – REVISED NOVEMBER 2008

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FUNCTIONAL DESCRIPTION

Operating on a single +3.0V supply, the ADC12DC080 digitizes two differential analog input signals to 12 bits,

using a differential pipelined architecture with error correction circuitry and an on-chip sample-and-hold circuit to

ensure maximum performance. The user has the choice of using an internal 1.2V stable reference, or using an

external 1.2V reference. Any external reference is buffered on-chip to ease the task of driving that pin. Duty cycle

stabilization and output data format are selectable using the quad state function OF/DCS pin (pin 19). The output

data can be set for offset binary or two's complement.

Applications Information

OPERATING CONDITIONS

We recommend that the following conditions be observed for operation of the ADC12DC080:

2.7V

≤ VA ≤ 3.6V

2.4V

≤ VDR ≤ VA

20 MHz

≤ fCLK ≤ 80 MHz

1.2V internal reference

VREF = 1.2V (for an external reference)

VCM = 1.5V (from VCMO)

ANALOG INPUTS

Signal Inputs

Differential Analog Input Pins

The ADC12DC080 has a pair of analog signal input pins for each of two channels. VIN+ and VIN− form a

differential input pair. The input signal, VIN, is defined as:

VIN = (VIN+) – (VIN−)

(4)

Figure 17 shows the expected input signal range. Note that the common mode input voltage, VCM, should be

1.5V. Using VCMO (pins 7,9) for VCM will ensure the proper input common mode level for the analog input signal.

The positive peaks of the individual input signals should each never exceed 2.6V. Each analog input pin of the

differential pair should have a maximum peak-to-peak voltage of 1V, be 180° out of phase with each other and

be centered around VCM.The peak-to-peak voltage swing at each analog input pin should not exceed the 1V or

the output data will be clipped.

Figure 17. Expected Input Signal Range

For single frequency sine waves the full scale error in LSB can be described as approximately:

EFS = 4096 ( 1 - sin (90° + dev))

(5)

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