AD6672 datasheet(20/32 Pages) AD

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AD6672

Rev. 0 | Page 20 of 32

DIGITAL OUTPUTS

The AD6672 output drivers can be configured for either ANSI

LVDS or reduced swing LVDS using a 1.8 V DRVDD supply.

As detailed in the AN-877 Application Note, Interfacing to High

Speed ADCs via SPI, the data format can be selected for offset

binary, twos complement, or gray code when using the SPI

control.

Digital Output Enable Function (OEB)

The AD6672 has a flexible three-state ability for the digital

output pins. The three-state mode is enabled using the SPI

interface. The data outputs can be three-stated by using the

output enable bar bit (Bit 4) in Register 0x14. This OEB

function is not intended for rapid access to the data bus.

Timing

The AD6672 provides latched data with a pipeline delay of

10 input sample clock cycles when NSR is disabled and provides

13 input sample clock cycles when NSR is enabled. Data outputs

are available one propagation delay (tPD) after the rising edge of

the clock signal.

Minimize the length of the output data lines as well as the loads

placed on these lines to reduce transients within the AD6672.

These transients may degrade converter dynamic performance.

The lowest typical conversion rate of the AD6672 is 40 MSPS. At

clock rates below 40 MSPS, dynamic performance may degrade.

Data Clock Output (DCO)

The AD6672 also provides the data clock output (DCO)

intended for capturing the data in an external register. Figure 2

shows a timing diagram of the AD6672 output modes.

ADC OVERRANGE (OR)

The ADC overrange indicator is asserted when an overrange is

detected on the input of the ADC. The overrange condition is

determined at the output of the ADC pipeline and, therefore, is

subject to a latency of 10 ADC clock cycles. An overrange at the

input is indicated by this bit 10 clock cycles after it occurs.

Table 10. Output Data Format

Input (V)

VIN+ − VIN−,

Input Span = 1.75 V p-p (V)

Offset Binary Output Mode

Twos Complement Mode (Default)

VIN+ − VIN−

<−0.875

000 0000 0000

100 0000 0000

VIN+ − VIN−

−0.875

000 0000 0000

100 0000 0000

VIN+ − VIN−

100 0000 0000

000 0000 0000

VIN+ − VIN−

+0.875

111 1111 1111

011 1111 1111

VIN+ − VIN−

>+0.875

111 1111 1111

011 1111 1111

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