AD5449 Analog Devices, AD5449 Datasheet - Page 19

• Manufacturer Part Number: AD5449
• Description: Dual 12-Bit, High Bandwidth Multiplying DAC with Serial Interface
• Manufacturer: Analog Devices

Specifications of AD5449

• Resolution (bits): 12bit
• Dac Update Rate: 2.47MSPS
• Dac Settling Time: 80ns
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Ser,SPI

REFERENCE SELECTION
When selecting a reference for use with the AD54xx series of
current output DACs, pay attention to the reference output voltage
temperature coefficient specification. This parameter affects not
only the full-scale error, but it 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 of 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 a low output
temperature coefficient, this error source can be minimized.
Table 7 lists some 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 input offset voltage. This output
Table 7. Suitable Analog Devices Precision References
Part No.
ADR01
ADR01
ADR02
ADR02
ADR03
ADR03
ADR06
ADR06
ADR431
ADR435
ADR391
ADR395
Table 8. Suitable Analog Devices Precision Op Amps
Part No.
OP97
OP1177
AD8551
AD8603
AD8628
Table 9. Suitable Analog Devices High Speed Op Amps
Part No.
AD8065
AD8021
AD8038
AD9631
Supply Voltage (V)
±2 to ±20
±2.5 to ±15
2.7 to 5
1.8 to 6
2.7 to 6
Output Voltage (V)
10
10
5
5
2.5
2.5
3
3
2.5
5
2.5
5
Supply Voltage (V)
5 to 24
±2.5 to ±12
3 to 12
±3 to ±6
Initial Tolerance (%)
0.05
0.05
0.06
0.06
0.10
0.10
0.10
0.10
0.04
0.04
0.16
0.10
V
25
60
5
50
5
BW @ ACL (MHz)
145
490
350
320
OS
(Max) (μV)
I
0.1
2
0.05
0.001
0.1
B
(Max) (nA)
Slew Rate (V/μs)
180
120
425
1300
Temp Drift (ppm/°C)
3
9
3
9
3
9
3
9
3
3
9
9
Rev. D | Page 19 of 28
0.1 Hz to 10 Hz Noise (μV p-p)
0.5
0.4
1
2.3
0.5
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. 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, 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 because 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.
If the DAC switches are driven from true wideband low impedance
sources (V
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 at the
V
DAC 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. Analog Devices offers a wide range of single-
supply amplifiers (see Table 8 and Table 9).
REF
VOS (Max) (μV)
1500
1000
3000
10,000
node (the voltage output node in this application) of the
IN
I
1
1
1
1
1
1
1
1
0.8
0.8
0.12
0.12
and AGND), they settle quickly. Consequently, the
SS
(mA)
I
6000
10,500
750
7000
B
Output Noise (μV p-p)
20
20
10
10
6
6
10
10
3.5
8
5
8
AD5429/AD5439/AD5449
(Max) (nA)
Supply Current (μA)
600
500
975
50
850
Package
SOIC-8, SOT-23, MSOP
SOIC-8, MSOP
SOIC-8, SC70-5
SOIC-8
Package
SOIC-8
TSOT-23, SC70
SOIC-8
TSOT-23, SC70
SOIC-8
TSOT-23, SC70
SOIC-8
TSOT-23, SC70
SOIC-8
SOIC-8
TSOT-23
TSOT-23
Package
SOIC-8
MSOP, SOIC-8
MSOP, SOIC-8
TSOT
TSOT, SOIC-8