Application information

RHF1201

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Output enable (OEB)

converter goes on sampling. When OEB is set to a low level again, the data arrives on the

Figure 3: Timing diagram on page 5 summarizes this functionality.

Slew rate control (SRC)

are twice as fast.

Out of range (OR)

This function is implemented on the output stage in order to set an “Out of Range” flag

whenever the digital data is over the full scale range.

Typically, there is a detection of all the data at ’0’ or all the data at ’1’. It sets an output signal

Data ready (DR)

The Data Ready output is an image of the clock being synchronized on the output data (D0

to D11). This is a very helpful signal that simplifies the synchronization of the measurement

equipment or of the controlling DSP.

As all other digital outputs, DR goes into high impedance state when OEB is set to high level

as shown in Figure 3: Timing diagram on page 5.

7.2

Driving the analog input

7.2.1

Differential inputs

The RHF1201is designed to obtain optimum performance when driven on differential inputs.

An RF transformer is an efficient way of achieving this high performance.

Figure 4: Differential input configuration describes the schematics. The input signal is fed to

the primary of the transformer, while the secondary drives both ADC inputs. The common

mode voltage of the ADC (INCM) is connected to the center-tap of the secondary of the

transformer in order to bias the input signal around this common voltage, internally set close

to 0.5V. The INCM is de-coupled to maintain a low noise level on this node. Our evaluation

board is mounted with a 1:1 ADT1-1 transformer from Minicircuits. You might also use a

higher impedance ratio (1:2 or 1:4) to reduce the driving requirement on the analog signal

source.