RHF1401

Application information

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7

Application information

The RHF1401 is a high speed analog-to-digital converter based on a pipeline architecture

and the ST 0.25µm CMOS process in order to achieve the best performance in terms of

linearity, power consumption and radiation hardness.

The pipeline structure consists of 14 internal conversion stages in which the analog signal is

fed and sequentially converted into digital data.

Each of the first 13 stages consists of an analog to digital converter, a digital to analog

converter, a sample and hold and an amplifier with a gain of 2. A 1.5-bit conversion

resolution is done at each stage. The last stage is a 2-bit flash ADC. Each resulting LSB-

MSB couple is then time-shifted to recover from the delay caused by conversion. Digital data

correction completes the processing by recovering from the redundancy of the (LSB-MSB)

couple for each stage. The corrected data is output through the digital buffers.

Signal input is sampled on the rising edge of the clock while digital outputs are synchronized

on the falling edge of the clock.

The advantages of this converter reside in the combination of a SEFI-free pipeline

architecture and advanced low-voltage CMOS technology. The highest dynamic

performance is achieved while consumption remains at the lowest level.

7.1

Analog input configuration

7.1.1

Setting the analog input range and references

To optimize the high resolution and speed of the RHF1401, we strongly advise you to drive

the analog input differentially. The half full-scale of RHF1401 is adjusted through the voltage

The differential analog input signal always has a common mode voltage of:

To select the references according to the constraints of your particular application, a control

pin, REFMODE, allows you to switch from internal to external references.

Internal references, common mode:

generated by its internal bandgap. If the VREFM pin is connected externally to the analog

ground while VREFP is set to its internal voltage (0.86 V), the full scale of the ADC is

2 x 0.86 = 1.72V.

In this case, VREFP, VREFM and INCM are low impedance outputs. The INCM pin (voltage

generator 0.46 V) may be used to supply the common mode, CM, of the analog input signal.

V

IN

V

INB

–

Full Scale

2 V

REFP

V

REFM

–

()

==

V

CM

V

IN

V

INB

+

2

----------------------------

=