Datasheet

AD9224

–11–REV. A

Table I. Analog Input Configuration Summary

Input Input ␣␣␣␣␣␣Input Range (V) Figure

Connection Coupling Span (V) VINA

VINB

# Comments

Single-Ended DC 2 0 to 2 1 19, 20 Best for stepped input response applications, requires ±5 V op amp.

2 × VREF 0 to VREF 19, 20 Same as above but with improved noise performance due to

2 × VREF increase in dynamic range. Headroom/settling time require-

ments of ±5 op amp should be evaluated.

4 0 to 4 2.0 19, 20 Optimum noise performance, excellent SNR performance, often

requires low distortion op amp with VCC > +5 V due to its head-

room issues.

2 × VREF 2.0 – VREF 2.0 30 Optimum THD performance with VREF = 1. Single supply

␣␣␣␣to operation (i.e., +5 V) for many op amps.

2.0 + VREF

Single-Ended AC 2 or 0 to 1 or 1 or VREF 21, 22

2 × VREF 0 to 2 × VREF

4 0.5 to 4.5 2.5 22 Optimum noise performance, excellent THD performance,

ability to use ±5 V op amp.

2 × VREF 2.0 – VREF 2.0 21 Flexible input range, Optimum THD performance with

␣␣␣␣to VREF = 1. Ability to use either +5 V or ±5 V op amp.

2.0 + VREF

Differential AC/DC 2 2 to 3 3 to 2 23, 24 Optimum full-scale THD and SFDR performance well beyond

(via Transformer) the A/Ds Nyquist frequency. Preferred mode for undersampling

or Amplifier applications.

2 × VREF 2.0 – VREF/2 2.0 + VREF/2 23, 24 Same as above with the exception that full-scale THD and SFDR

␣␣␣␣to ␣␣␣␣to performance can be traded off for better noise performance.

2.0 + VREF/2 2.0 – VREF/2

4.0 1.5 to 3.5 3.5 to 1.5 23, 24 Optimum noise performance.

NOTE

VINA and VINB can be interchanged if signal inversion is required.

Table II. Reference Configuration Summary

Reference Input Span (VINA–VINB)

Operating Mode (V p-p) Required VREF (V) Connect To

INTERNAL 2 1 SENSE VREF

INTERNAL 4 2 SENSE REFCOM

INTERNAL 2 ≤ SPAN ≤ 4 AND 1 ≤ VREF ≤ 2.0 AND R1 VREF AND SENSE

SPAN = 2

VREF VREF = (1 + R1/R2) R2 SENSE AND REFCOM

EXTERNAL 2 ≤ SPAN ≤ 41 ≤ VREF ≤ 2.0 SENSE AVDD

(NONDYNAMIC) VREF EXT. REF.

EXTERNAL 2 ≤ SPAN ≤ 4 CAPT and CAPB SENSE AVDD

(DYNAMIC) Externally Driven VREF AVSS

EXT. REF. CAPT

EXT. REF. CAPB