AD5522JSVDZ datasheet(57/60 Pages) AD

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AD5522

Rev. A | Page 57 of 60

Table 38. ADCs and ADC Drivers Suggested For Use with AD55221

Part No.

Resolution

Sample

Rate

Ch.

No.

AIN Range

Interface

ADC Driver

Multiplexer2

Package

AD7685

250 kSPS

0 to VREF

Serial, SPI

ADA4841-x

ADG704, ADG708

MSOP,

LFCSP

AD7686

500 kSPS

0 to VREF

Serial, SPI

ADA4841-x

ADG704, ADG708

MSOP,

LFCSP

AD7693

500 kSPS

−VREF to +VREF

Serial, SPI

ADA4841-x,

ADA4941-1

ADG1404, ADG1408,

ADG1204

MSOP,

LFCSP

AD76103

250 kSPS

Bipolar 10 V, Bipolar

5 V, Unipolar 10 V,

Unipolar 5 V

Serial/Parallel

AD8021

ADG1404, ADG1408,

ADG1204

LFCSP,

LQFP

AD7655

1 MSPS

0 V to 5 V

Serial/Parallel

ADA4841-x/

AD8021

1 Subset of the possible ADCs suitable for use with the AD5522. Visit www.analog.com for more options

2 For purposes of sharing an ADC among multiple PMU channels. Note, that the multiplexer is not absolutely necessary as the AD5522 MEASOUTx path has a tri-state

mode per channel.

3 Do not allow the MEASOUT output range to exceed the AIN range of the ADC

POWER SUPPLY DECOUPLING

Careful consideration of the power supply and ground return

layout helps to ensure the rated performance. Design the

printed circuit board (PCB) on which the AD5522 is mounted

so that the analog and digital sections are separated and

confined to certain areas of the board. If the AD5522 is in a

system where multiple devices require an AGND-to-DGND

connection, the connection should be made at one point only.

Establish the star ground point as close as possible to the device.

For supplies with multiple pins (AVSS and AVDD), it is

recommended that these pins be tied together and that each

supply be decoupled only once.

The AD5522 should have ample supply decoupling 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 capac-

itors should have low effective series resistance (ESR) and low

effective series inductance (ESL)—typical of the common

ceramic types that provide a low impedance path to ground at

high frequencies—to handle transient currents due to internal

logic switching.

Avoid running digital lines under the device because they can

couple noise onto the device. However, allow the analog ground

plane to run under the AD5522 to avoid noise coupling (applies

only to the package with paddle up). The power supply lines of

the AD5522 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 digital signals should be

shielded with digital ground to avoid radiating noise to other

parts of the board, and they should never be run near the refer-

ence inputs. It is essential to minimize noise on all VREF lines.

Avoid crossover of digital and analog signals. Traces on opposite

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

reduce the effects of feedthrough through the board. 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 this

package during the assembly process.

Also, note that the exposed paddle of the AD5522 is connected

to the negative supply, AVSS.

POWER SUPPLY SEQUENCING

When the supplies are connected to the AD5522, it is important

that the AGND and DGND pins be connected to the relevant

ground planes before the positive or negative supplies are applied.

This is the only power sequencing requirement for this device.

TYPICAL APPLICATION FOR THE AD5522

Figure 56 shows the AD5522 used in an ATE system. The device

can be used as a per-pin parametric unit to speed up the rate at

which testing can be done.

The central PMU (shown in the block diagram) is usually a

highly accurate PMU and is shared among a number of pins

in the tester. In general, many discrete levels are required in an

ATE system for the pin drivers, comparators, clamps, and active

loads. DAC devices such as the AD537x family offer a highly

integrated solution for a number of these levels.

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