AD5453YUJ-REEL7 Analog Devices Inc, AD5453YUJ-REEL7 Datasheet - Page 19

• Manufacturer Part Number: AD5453YUJ-REEL7
• Description: IC DAC 14BIT MULT TSOT23-8
• Manufacturer: Analog Devices Inc

Specifications of AD5453YUJ-REEL7

• Design Resources: Unipolar, Precision DC Digital-to-Analog Conversion using AD5450/1/2/3 8-14-Bit DACs (CN0052) Precision, Bipolar, Configuration for AD5450/1/2/3 8-14bit Multiplying DACs (CN0053) AC Signal Processing Using AD5450/1/2/3 Current Output DACs (CN0054) Programmable Gain Element Using AD5450/1/2/3 Current Output DAC Family (CN0055)
• Settling Time: 180ns
• Number Of Bits: 14
• Data Interface: Serial
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Power Dissipation (max): 55µW
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: TSOT-23-8, TSOT-8
• For Use With: EVAL-AD5453EB - BOARD EVAL FOR AD5453
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

DIVIDER OR PROGRAMMABLE GAIN ELEMENT
Current-steering DACs are very flexible and lend themselves to
many different applications. If this type of DAC is connected as
the feedback element of an op amp and R
resistor as shown in Figure 48, the output voltage is inversely
proportional to the digital input fraction, D.
For D = 1 − 2
As D is reduced, the output voltage increases. For small values
of the digital fraction, D, it is important to ensure that the
amplifier does not saturate and that the required accuracy is
met. For example, an 8-bit DAC driven with the binary code
0x10 (00010000), that is, 16 decimal, in the circuit of Figure 48
should cause the output voltage to be 16 times V
However, if the DAC has a linearity specification of ±0.5 LSB, D
can have weight anywhere in the range of 15.5/256 to 16.5/256.
Therefore, the possible output voltage is in the range of 15.5 V
to 16.5 V
maximum error of 0.2%.
DAC leakage current is also a potential error source in divider
circuits. The leakage current must be counterbalanced by an
opposite current supplied from the op amp through the DAC.
Because only a fraction, D, of the current in the V
routed to the I
where R is the DAC resistance at the V
For a DAC leakage current of 10 nA, R = 10 kΩ, and a gain
(that is, 1/D) of 16, the error voltage is 1.6 mV.
REFERENCE SELECTION
When selecting a reference for use with this series of current-
output DACs, pay attention to the reference’s output voltage
V
Output
OUT
IN
Figure 48. Current-Steering DAC Used as a Divider or
—an error of 3%, even though the DAC itself has a
=
Error
−
−n
NOTE
ADDITIONAL PINS OMITTED FOR CLARITY
OUT
V
D
, the output voltage is
IN
1 terminal, the output voltage changes as follows:
V
Voltage
=
IN
Programmable Gain Element
I
OUT
(
1
−
−
1
V
R
2
FB
IN
−
Due
n
GND
)
V
V
DD
DD
to
V
Leakage
REF
REF
FB
terminal.
=
is used as the input
(
Leakage
V
OUT
IN
REF
.
terminal is
×
R
/ )
D
Rev. B | Page 19 of 28
IN
temperature coefficient specification. This parameter not only
affects the full-scale error, but also may 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 is required to hold its overall
specification to within 1 LSB over the temperature range 0°C to
50°C, and the system’s maximum temperature drift should be
less than 78 ppm/°C.
A 12-bit system within 2 LSB accuracy requires a maximum
drift of 10 ppm/°C. Choosing a precision reference with a low
output temperature coefficient minimizes this error source.
Table 7 lists some dc 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 of the circuit due to the code-dependent output resistance
of the DAC. A change in this noise gain between two adjacent
digital fractions produces a step change in the output voltage
due to the offset voltage of the amplifier’s input. 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.
The input bias current of an op amp generates an offset at the
voltage output as a result of the bias current flowing in the
feedback resistor, R
low enough to prevent significant errors in 12-bit applications.
However, for 14-bit applications, some consideration should be
given to selecting an appropriate amplifier.
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 resolutions.
Provided that the DAC switches are driven from true wideband
low impedance sources (V
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
output node in this application) 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.
AD5450/AD5451/AD5452/AD5453
FB
. Most op amps have input bias currents
IN
and AGND), they settle quickly.
REF
node (the voltage