REV. A

AD5532B

–15–

APPLICATION CIRCUITS

AD5532B in a Typical ATE System

The AD5532B 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 these applications.

The AD5532B 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 15).

DACs

ACTIVE

LOAD

DRIVER

COMPARATOR

FORMATTER

COMPARE

REGISTER

STORED

DATA

AND INHIBIT

PATTERN

PERIOD

GENERATION

AND

DELAY

TIMING

SYSTEM BUS

DAC

PARAMETRIC

MEASUREMENT

UNIT

SYSTEM BUS

DUT

DAC

DAC

DAC

DAC

DAC

DAC

Figure 15. AD5532B in an ATE System

Typical Application Circuit (DAC Mode)

The AD5532B can be used in many optical networking applications

that require a large number of DACs to perform control and

measurement functions. In the example shown in Figure 16, the

outputs of the AD5532B are amplified and 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-2191M, a 16-bit fixed-

point DSP with three SPORT interfaces and two SPI ports. The

DSP uses some of these serial ports to write data to the DAC,

control the multiplexer, and read back data from the ADC.

ADSP-2191M

AD5532B

MEMS

MIRROR

ARRAY

ADG739

4

AD7856

1

32

S

E

N

S

O

R

AD8544

2

1

32

1

8

Figure 16. Typical Optical Control and

Measurement Application Circuit

Typical Application Circuit (ISHA Mode)

The AD5532B 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 AD5532B, and for the AD5541 16-bit DAC. A simple

3-wire serial interface is used to write to the AD5541. Because

the AD5541 has an output resistance of 6.25 kW (typ), the time

cant. Thus an AD820 is used to buffer the DAC output. Note

laying out this circuit.

AD5532B*

OFFS_IN

OFFS_OUT

REFIN

SCLK

DIN

SYNC

AD820

CS

DIN

SCLK

*ADDITIONAL PINS OMITTED FOR CLARITY

AD780*

AD5541*

REF

Figure 17. Typical Application Circuit (ISHA Mode)

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

AD5532B is mounted should be designed so that the analog and

digital sections are separated, and confined to certain areas of the

board. If the AD5532B 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

The AD5532B 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 induc-

tance (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.