Detailed description – Rainbow Electronics MAX1201 User Manual

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+5V Single-Supply, 2.2Msps, 14-Bit
Self-Calibrating ADC

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Detailed Description

Converter Operation

The MAX1201 is a 14-bit, monolithic, analog-to-digital
converter (ADC) capable of conversion rates up to
2.2Msps. It uses a multistage, fully differential, pipe-
lined architecture with digital error correction and self-
calibration to provide 90dB (typ) spurious-free dynamic
range at a 2.2Msps sampling rate. Its signal-to-noise
ratio, harmonic distortion, and intermodulation products
are also consistent with 14-bit accuracy up to the
Nyquist frequency. This makes the device suitable for
applications such as xDSL, digital radio, instrumenta-
tion, and imaging.

Figure 1 shows the simplified, internal structure of the
ADC. A switched-capacitor pipelined architecture is
used to digitize the signal at a high throughput rate.
The first four stages of the pipeline use a low resolution
quantizer to approximate the input signal. The multiply-
ing digital-to-analog converter (MDAC) stage is used to
subtract the quantized analog signal from the input.
The residue is then amplified with a fixed gain and
passed on to the next stage. The accuracy of the con-
verter is improved by a digital calibration algorithm
which corrects for mismatches between the capacitors

in the switched capacitor MDAC. Note that the pipeline
introduces latency of four sampling periods between
the input being sampled and the output appearing at
D13–D0. While the device can handle both single-
ended or differential inputs (see

Requirements for

Reference and Analog Signal Inputs

), the latter mode of

operation will guarantee best THD and SFDR perfor-
mance. The differential input provides the following
advantages compared to a single-ended operation:

•

Twice as much signal input span

•

Common-mode noise immunity

•

Virtual elimination of the even-order harmonics

•

Less stringent requirements on the input signal pro-
cessing amplifiers

Requirements for Reference

and Analog Signal Inputs

Fully differential switched capacitor circuits (SC) are
used for both the reference and analog inputs (Figure
2). This allows either single-ended or differential signals
to be used in the reference and/or analog signal paths.
The signal voltage on these pins (INP, INN, RFP_,
RFN_) should neither exceed the analog supply rail,
AV

nor fall below ground.

STAGE1

DAV

INP

RFN_

RFP_

AGND

INN

CLK

DGND

DRV

ST_CAL

DOR

D13–D0

ADC

MDAC

S/H

STAGE2

STAGE3

STAGE4

CORRECTION AND

CALIBRATION LOGIC

END_CAL

OUTPUT DRIVERS

CLOCK

GENERATOR

MAX1201

Figure 1. Internal Block Diagram