AD5424 datasheet(21/32 Pages) AD

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AD5424/AD5433/AD5445

Rev. B | Page 21 of 32

Table 9. Suitable ADI Precision References

Part No.

Output Voltage (V)

Initial Tolerance (%)

Temp Drift (ppm/°C)

ISS (mA)

Output Noise (μV p-p)

Package

ADR01

0.05

SOIC-8

ADR01

0.05

TSOT-23, SC70

ADR02

0.06

SOIC-8

ADR02

0.06

TSOT-23, SC70

ADR03

2.5

0.10

SOIC-8

ADR03

2.5

0.10

TSOT-23, SC70

ADR06

0.10

SOIC-8

ADR06

0.10

TSOT-23, SC70

ADR431

2.5

0.04

0.8

3.5

SOIC-8

ADR435

0.04

0.8

SOIC-8

ADR391

2.5

0.16

0.12

TSOT-23

ADR395

0.10

0.12

TSOT-23

Table 10. Suitable ADI Precision Op Amps

Part No.

Supply Voltage (V)

VOS (Max) (μV)

IB (Max) (nA)

0.1 Hz to 10 Hz

Noise (μV p-p)

Supply Current (μA)

Package

OP97

±2 to ±20

0.1

0.5

600

SOIC-8

OP1177

±2.5 to ±15

0.4

500

MSOP, SOIC-8

AD8551

2.7 to 5

0.05

975

MSOP, SOIC-8

AD8603

1.8 to 6

0.001

2.3

TSOT

AD8628

2.7 to 6

0.1

0.5

850

TSOT, SOIC-8

Table 11. Suitable ADI High Speed Op Amps

Part No.

Supply Voltage (V)

BW @ ACL (MHz)

Slew Rate (V/μs)

VOS (Max) (μV)

IB (Max) (nA)

Package

AD8065

5 to 24

145

180

1500

6000

SOIC-8, SOT-23,MSOP

AD8021

±2.5 to ±12

490

120

1000

10500

SOIC-8, MSOP

AD8038

3 to 12

350

425

3000

750

SOIC-8, SC70-5

AD9631

±3 to ±6

320

1300

10000

7000

SOIC-8

REFERENCE SELECTION

When selecting a reference for use with the AD5424/AD5433/

AD5445 family of current output DACs, pay attention to the

reference’s output voltage temperature coefficient specification.

This parameter not only affects the full-scale error, but can also

affect the linearity (INL and DNL) performance. The reference

temperature coefficient should be consistent with the system

accuracy specifications. For example, an 8-bit system required

to hold its overall specification to within 1 LSB over the temp-

erature range 0°C to 50°C dictates that the maximum system

drift with temperature should be less than 78 ppm/°C.

A 12-bit system with the same temperature range to overall

specification within 2 LSBs requires a maximum drift of

10 ppm/°C. By choosing a precision reference with low output

temperature coefficient this error source can be minimized.

Table 9 suggests some references available from Analog Devices

that are suitable for use with this range of current output DACs.

AMPLIFIER SELECTION

The primary requirement for the current-steering mode is an

amplifier with low input bias currents and low input offset

voltage. The input offset voltage of an op amp is multiplied by

the variable gain (due to the code dependent output resistance

of the DAC) of the circuit. A change in the noise gain between

two adjacent digital fractions produces a step change in the

output voltage due to the amplifier’s input offset voltage. This

output voltage change is superimposed on the desired change in

output between the two codes and gives rise to a differential

linearity error, which, if large enough, could cause the DAC to

be nonmonotonic. In general, the input offset voltage should

be <1/4 LSB to ensure monotonic behavior when stepping

through codes.

The input bias current of an op amp also generates an offset

at the voltage output as a result of the bias current flowing

into the feedback resistor, RFB. Most op amps have input bias

currents low enough to prevent significant errors in

12-bit applications.

Common-mode rejection of the op amp is important in

voltage-switching circuits, since it produces a code dependent

error at the voltage output of the circuit. Most op amps have

adequate common mode rejection for use at 8-, 10-, and 12-bit

resolution.

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