Datasheet

Data Sheet AD5426/AD5432/AD5443
Rev. G | Page 19 of 24
a fraction (~ <1/4) of an 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 in the
feedback resistor, R
FB
. Most op amps have input bias currents low
enough to prevent any 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 at an 8-, 10-, or 12-bit resolution.
Provided the DAC switches are driven from true wideband low
impedance sources (V
IN
and AGND), they settle quickly.
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, it is
important to minimize capacitance at the V
REF
of the DAC. This
is done by using low input capacitance buffer amplifiers and
careful board design. Most single-supply circuits include ground as
part of the analog signal range, which in turn requires an amplifier
that can handle rail-to-rail signals,. There is a large range of
single-supply amplifiers available from Analog Devices.
Table 7. 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 8. 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 9. Suitable ADI High Speed Op Amps
Part No. Supply Voltage (V) BW @ A
CL
(MHz) Slew Rate (V/µs) V
OS
(Max) (µV) I
B
(Max) (nA) Package
AD8065 5 to 24 145 180 1,500 6,000 SOIC-8, SOT-23, MSOP
AD8021 ±2.5 to ±12 490 100 1,000 10,500 SOIC-8, MSOP
AD8038 3 to 12 350 425 3,000 750 SOIC-8, SC70-5
AD9631 ±2 to ±6 320 1,300 10,000 7,000 SOIC-8