REV. 0

AD5532HS

–10–

APPLICATION CIRCUITS

AD5532HS in an Optical Network Control Loop

The AD5532HS can be used in optical network applications

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

measurement function. In the circuit shown in Figure 7, the

0 V–5 V outputs of the AD5532HS are amplified to a range of

0 V–180 V and then used to control actuators that determine

the position of MEMS mirrors in an optical switch. The exact

position of each mirror is measured using sensors. The sensor

readings are muxed using four dual 4-channel matrix switches

(ADG739) and fed back to an 8-channel 14-bit ADC (AD7856).

The control loop is driven by an ADSP-21065L, a 32-bit SHARC

®

DSP with an SPI-compatible SPORT interface. It writes data

to the DAC, controls the multiplexor, and reads data from

the ADC via a 3-wire serial interface.

0V–180V

AMPS

ACTUATORS

FOR MEMS

MIRROR

ARRAY

AD7856

ADSP-21065L

S

E

N

S

O

R

S

1

32

1

32

1

8

ADG739

4

AD5532HS

Figure 7. AD5532HS and DSP Control an Optical Switch

Alternatively, the AD5532HS can be driven by an ADMC401

Motor-Controller as shown in the control-loop in Figure 8. The

DAC outputs are fed into eight AD8534 quad transconductance

amps to generate currents for voice-coil actuators that determine

the position of the mirrors. The exact position of each mirror

is measured and the readings are muxed into the on-chip

8-channel ADC of the ADMC401.

1

32

AD5532HS

AD8534

8

ADMC401

S

E

N

S

O

R

S

1

8

ADG704

8

S

P

O

R

T

3

AD8544

2

3

8-CH

12-BIT

ADC

1

8

1

32

VOICE-COIL

ACTUATORS

FOR

MEMS

MIRROR

ARRAY

Figure 8. AD5532HS and ADMC401 Control an Optical

Switch

AD5532HS in a Typical ATE System

The AD5532HS is ideally suited for use in Automatic Test

Equipment. Several DACs are required to control pin drivers,

comparators, active loads, and signal timing. Traditionally,

sample-and-hold devices were used in this application.

The AD5532HS 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. A higher level of

integration is achieved in a smaller area (see Figure 9).

DACs

ACTIVE

LOAD

DRIVER

COMPARATOR

FORMATTER

COMPARE

REGISTER

STORED

DATA

AND INHIBIT

PATTERN

PERIOD

GENERATION

AND

DELAY

TIMING

SYSTEM BUS

SYSTEM BUS

DUT

DAC

DAC

DAC

DAC

DAC

DAC

DAC

PARAMETRIC

MEASUREMENT

UNIT

Figure 9. AD5532HS in an ATE System

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

AD5532HS is mounted should be designed so that the analog

and digital sections are separated, and confined to certain areas

of the board. If the AD5532HS 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

tie those pins together. The AD5532HS 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 AD5532HS 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 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 REF_IN.

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.

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.

SHARC is a registered trademark of Analog Devices, Inc.