AD5533

–15–

REV. 0

APPLICATION CIRCUITS

AD5533 in a Typical ATE System

The AD5533 Infinite Sample-and-Hold is ideally suited for use

in Automatic Test Equipment. Several SHAs are required to

control pin drivers, comparators, active loads, and signal timing.

Traditionally, sample-and-hold devices with droop were used in

this application. These required refreshing to prevent the volt-

age from drifting.

The AD5533 has several advantages: no refreshing is required,

there is no droop, pedestal error is eliminated, and there is no

need for extra filtering to remove glitches. Overall, a higher level

of integration is achieved in a smaller area, see Figure 18.

SHAs

ACTIVE

LOAD

DRIVER

COMPARATOR

FORMATTER

COMPARE

REGISTER

STORED

DATA

AND INHIBIT

PATTERN

PERIOD

GENERATION

AND

DELAY

TIMING

SYSTEM BUS

SHA

PARAMETRIC

MEASUREMENT

UNIT

SYSTEM BUS

DUT

SHA

SHA

SHA

SHA

SHA

SHA

Figure 18. AD5533 in an ATE System

Typical Application Circuit

The AD5533 can be used to set up voltage levels on 32 channels

as shown in the circuit below. An AD780 provides the 3 V refer-

ence for the AD5533, and for the AD5541 16-bit DAC. A simple

3-wire interface is used to write to the AD5541. The DAC out-

put is buffered by an AD820. It is essential to minimize noise on

AD5533*

OFFS_IN

OFFS_OUT

REFIN

SCLK

DIN

SYNC

AD820

CS

DIN

SCLK

*ADDITIONAL PINS OMITTED FOR CLARITY

AD780*

AD5541*

REF

Figure 19. Typical Application Circuit

POWER SUPPLY DECOUPLING

In any circuit where accuracy is important, careful consideration

of the power supply and ground return layout helps to ensure

the rated performance. The printed circuit board on which the

AD5533 is mounted should be designed so that the analog and

digital sections are separated, and confined to certain areas of

the board. If the AD5533 is in a system where multiple devices

require an AGND-to-DGND connection, the connection should

be made at one point only. The star ground point should be

established as close as possible to the device. For supplies with

together. The AD5533 should have ample supply bypassing of

10

µF in parallel with 0.1 µF on each supply located as close to

the package as possible, ideally right up against the device. The

10

µF capacitors are the tantalum bead type. The 0.1 µF capacitor

should have low Effective Series Resistance (ESR) and Effective

Series Inductance (ESI), like the common ceramic types that

provide a low impedance path to ground at high frequencies, to

handle transient currents due to internal logic switching.

The power supply lines of the AD5533 should use as large a trace

as possible to provide low impedance paths and reduce the effects

of glitches on the power supply line. Fast switching signals such

as clocks should be shielded with digital ground to avoid radiat-

ing noise to other parts of the board, and should never be run

near the reference inputs. A ground line routed between the

required on a multilayer board as there will be a separate ground

plane, but separating the lines will help). It is essential to mini-

Avoid crossover of digital and analog signals. Traces on opposite

sides of the board should run at right angles to each other. This

reduces the effects of feedthrough through the board. A microstrip

technique is by far the best, but not always possible with a double-

sided board. In this technique, the component side of the board

is dedicated to ground plane while signal traces are placed on

the solder side.