AD5543BRZ Analog Devices Inc, AD5543BRZ Datasheet - Page 12

• Manufacturer Part Number: AD5543BRZ
• Description: IC DAC 16BIT SRLIN/CUR OUT 8SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD5543BRZ

• Data Interface: Serial
• Design Resources: Versatile High Precision Programmable Current Sources Using DACs, Op Amps, and MOSFET Transistors (CN0151)
• Settling Time: 500ns
• Number Of Bits: 16
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Power Dissipation (max): 55µW
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Resolution (bits): 16bit
• Sampling Rate: 1.2MSPS
• Input Channel Type: Serial
• Supply Voltage Range - Analog: 4.5V To 5.5V
• Supply Current: 10µA
• Digital Ic Case Style: SOIC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD5543/AD5553
PROGRAMMABLE CURRENT SOURCE
Figure
improved Howland current pump. In addition to the precision
current conversion it provides, this circuit enables a bidirectional
current flow and high voltage compliance. This circuit can be used
in 4 mA to 20 mA current transmitters with up to 500 Ω of load. In
Figure
the load current is
R3 in theory can be made small to achieve the current needed
within the U3 output current driving capability. This circuit is
versatile such that
and the voltage compliance approaches 15 V, which is limited
mainly by the supply voltages of U3. However, users must pay
attention to the compensation. Without C1, it can be shown
that the output impedance becomes
If the resistors are perfectly matched, Z
desirable, and behaves as an ideal current source. On the other
hand, if they are not matched, Z
Negative can cause oscillation. As a result, C1 is needed to prevent
the oscillation. For critical applications, C1 could be found
empirically but typically falls in the range of a few picofarads (pF).
V
Figure
REF
I
Z
AD5543/AD5553
L
23
23
23
O
U1
V
. Programmable Current Source with Bidirectional Current Control

, it can be shown that if the resistor network is matched,
REF
GND

V
V
shows a versatile V-I conversion circuit using an
DD
DD

R2
R1

R
and High Voltage Compliance Capabilities
R2

FB
R3
R3
'
AD8510
R1

I
OUT

/
'
R3
R3
R1
'



R1

can deliver ±20 mA in both directions
U2
V
R1
AD8628

REF
'
R2

O
R2

can be either positive or negative.

D

R3
150kΩ
150kΩ
R1

O
R1'
is infinite, which is
15kΩ
R2'
AD8510
15kΩ
10pF
V+
V–
V
V
C1
R2
SS
DD
U3
LOAD
R3'
50Ω
R3
50Ω
V
L
I
Rev. E | Page 12 of 20
L
(5)
(6)
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 7 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
feedback resistor, R
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
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,
minimize capacitance at the V
in this application) of 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 8 and Table 9.
FB
.
IN
and AGND), they settle quickly.
REF
node (the voltage output node