Datasheet

AD5424/AD5433/AD5445 Data Sheet
Rev. D | Page 22 of 28
Table 9. Suitable ADI Precision References
Part No. Output Voltage (V) Initial Tolerance (%) Temp Drift (ppm/°C) I
SS
(mA) Output Noise (µV p-p) Package
ADR01 10 0.05 3 1 20 SOIC-8
ADR01 10 0.05 9 1 20 TSOT-23, SC70
ADR02 5 0.06 3 1 10 SOIC-8
ADR02 5 0.06 9 1 10 TSOT-23, SC70
ADR03 2.5 0.10 3 1 6 SOIC-8
ADR03 2.5 0.10 9 1 6 TSOT-23, SC70
ADR06 3 0.10 3 1 10 SOIC-8
ADR06 3 0.10 9 1 10 TSOT-23, SC70
ADR431 2.5 0.04 3 0.8 3.5 SOIC-8
ADR435 5 0.04 3 0.8 8 SOIC-8
ADR391 2.5 0.16 9 0.12 5 TSOT-23
ADR395 5 0.10 9 0.12 8 TSOT-23
Table 10. Suitable ADI Precision Op Amps
Part No. Supply Voltage (V) V
OS
(Max) (µV) I
B
(Max) (nA)
0.1 Hz to 10 Hz
Noise (µV p-p) Supply Current (µA) Package
OP97
±2 to ±20
25
0.1
0.5
600
SOIC-8
OP1177 ±2.5 to ±15 60 2 0.4 500 MSOP, SOIC-8
AD8551 2.7 to 5 5 0.05 1 975 MSOP, SOIC-8
AD8603 1.8 to 6 50 0.001 2.3 50 TSOT
AD8628 2.7 to 6 5 0.1 0.5 850 TSOT, SOIC-8
Table 11. Suitable ADI High Speed Op Amps
Part No. Supply Voltage (V) BW at ACL (MHz) Slew Rate (V/µs) V
OS
(Max) (µV) I
B
(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
temperature 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 non-
monotonic. 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, R
FB
. 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.