AD5516 datasheet(13/16 Pages) AD

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AD5516

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APPLICATION CIRCUITS

The AD5516 is suited for use in many applications, such as level

setting, optical, industrial systems, and automatic test applica-

tions. In level setting and servo applications where a fine-tune

adjust is required, the Mode 2 function increases resolution.

The following figures show the AD5516 used in some potential

applications.

AD5516 in a Typical ATE System

The AD5516 is ideally suited for the level setting function in

automatic test equipment. A number of DACs are required to

control pin drivers, comparators, active loads, parametric mea-

surement units, and signal timing. Figure 10 shows the AD5516

in such a system.

DAC

STORED

DATA AND

INHIBIT

PATTERN

PERIOD

GENERATION

AND

DELAY

TIMING

DACs

FORMATTER

COMPARE

SYSTEM BUS

DAC

ACTIVE

LOAD

PARAMETRIC

MEASUREMENT

UNIT

SYSTEM BUS

DAC

COMPARATOR

DUT

DRIVER

Figure 10. AD5516 in an ATE System

AD5516 in an Optical Network Control Loop

The AD5516 can be used in optical network control applica-

tions that require a large number of DACs to perform a control

and measurement function. In the example shown below, the

outputs of the AD5516 are fed into amplifiers and used to control

actuators that determine the position of MEMS mirrors in an

optical switch. The exact position of each mirror is measured and

the readings are multiplexed into an 8-channel, 14-bit ADC

(AD7865). The increment and decrement modes of the DACs are

useful in this application as it allows the user 14-bit resolution.

The control loop is driven by an ADSP-2106x, a 32-bit

SHARC DSP.

AD5516

MEMS

MIRROR

ARRAY

ADG609

AD7865

AD8644

ADSP-2106x

Figure 11. AD5516 in an Optical Control Loop

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 AD5516

is mounted should be designed so that the analog and digital

sections are separated and confined to certain areas of the board. If

the AD5516 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 multiple pins

(AVCC1, AVCC2) it is recommended to tie those pins together. The

AD5516 should have ample supply bypassing of 10

µF in parallel

with 0.1

µF on each supply located as closely 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 AD5516 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 radiating

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

the reference inputs. A ground line routed between the DIN and

SCLK lines will help reduce crosstalk between them (not required

on a multilayer board as there will be a separate ground plane, but

separating the lines will help). It is essential to minimize noise

on REFIN.

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 micro-

strip 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.

As is the case for all thin packages, care must be taken to avoid

flexing the package and to avoid a point load on the surface of

the package during the assembly process.

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