AD5547/AD5557

Data Sheet

Rev. D | Page 18 of 20

REFERENCE SELECTION

When selecting a reference for use with the AD55xx series of

current output DACs, pay attention to the output voltage,

temperature coefficient specification of the reference. Choosing

a precision reference with a low output temperature coefficient

minimizes error sources. Table 10 lists some of the references

available from Analog Devices, Inc., 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.

Because of the code-dependent output resistance of the DAC,

the input offset voltage of an op amp is multiplied by the variable

gain of the circuit. A change in this 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 upon the desired change in output

between the two codes and gives rise to a differential linearity error,

which, if large enough, can cause the DAC to be nonmonotonic.

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

the voltage output because of the bias current flowing in the

Common-mode rejection of the op amp is important in voltage-

switching circuits because it produces a code-dependent error

at the voltage output of the circuit.

Provided that the DAC switches are driven from true wideband

Consequently, the slew rate and settling time of a voltage-switching

DAC circuit is determined largely by the output op amp. To obtain

minimum settling time in this configuration, minimize capacitance

the DAC. This is done by using low input capacitance buffer

amplifiers and careful board design.

Analog Devices offers a wide range of amplifiers for both precision

dc and ac applications, as listed in Table 11 and Table 12.

Table 10. Suitable Analog Devices Precision References

Part No.

Output Voltage (V)

Initial Tolerance (%)

Maximum Temperature

Drift (ppm/°C)

I

Output Noise (µV p-p)

Package(s)

ADR01

10

0.05

3

1

20

SOIC-8

ADR01

10

0.05

9

1

20

TSOT-5, SC70-5

ADR02

5.0

0.06

3

1

10

SOIC-8

ADR02

5.0

0.06

9

1

10

TSOT-5, SC70-5

ADR03

2.5

0.1

3

1

6

SOIC-8

ADR03

2.5

0.1

9

1

6

TSOT-5, SC70-5

ADR06

3.0

0.1

3

1

10

SOIC-8

ADR06

3.0

0.1

9

1

10

TSOT-5, SC70-5

ADR420

2.048

0.05

3

0.5

1.75

SOIC-8, MSOP-8

ADR421

2.50

0.04

3

0.5

1.75

SOIC-8, MSOP-8

ADR423

3.00

0.04

3

0.5

2

SOIC-8, MSOP-8

ADR425

5.00

0.04

3

0.5

3.4

SOIC-8, MSOP-8

ADR431

2.500

0.04

3

0.8

3.5

SOIC-8, MSOP-8

ADR435

5.000

0.04

3

0.8

8

SOIC-8, MSOP-8

ADR391

2.5

0.16

9

0.12

5

TSOT-5

ADR395

5.0

0.10

9

0.12

8

TSOT-5

Table 11. Suitable Analog Devices Precision Op Amps

Part No.

Supply Voltage (V)

V

(µV)

I

(nA)

0.1 Hz to 10 Hz

Noise (µV p-p)

Supply Current (µA)

Package(s)

OP97

±2 to ±20

25

0.1

0.5

600

SOIC-8 , PDIP-8

OP1177

±2.5 to ±15

60

2

0.4

500

MSOP-8, SOIC-8

AD8675

±5 to ±18

75

2

0.1

2300

MSOP-8, SOIC-8

AD8671

±5 to ±15

75

12

0.077

3000

MSOP-8, SOIC-8

ADA4004-1

±5 to ±15

125

90

0.1

2000

SOIC-8, SOT-23-5

AD8603

1.8 to 5

50

0.001

2.3

40

TSOT-5

AD8607

1.8 to 5

50

0.001

2.3

40

MSOP-8, SOIC-8

AD8605

2.7 to 5

65

0.001

2.3

1000

WLCSP-5, SOT-23-5

AD8615

2.7 to 5

65

0.001

2.4

2000

TSOT-5

AD8616

2.7 to 5

65

0.001

2.4

2000

MSOP-8, SOIC-8