AD5450/AD5451/AD5452/AD5453*
a
REV. PrD Oct, 2003
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
Analog Devices, Inc., 2003
8/10/12/14-Bit High Bandwidth
Multiplying DACs with Serial Interface
Preliminary Technical Data
PRELIMINARY TECHNICAL DATA
*US Patent Number 5,689,257
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corporation.
FEATURES
+2.5 V to +5.5 V Supply Operation
50MHz Serial Interface
10MHz Multiplying Bandwidth
10V Reference Input
8-Lead TSOT & MSOP Packages
Pin Compatible 8, 10, 12 and 14 Bit Current Output DACs
Extended Temperature range 40C to +125C
Guaranteed Monotonic
Four Quadrant Multiplication
Power On Reset with brown out detect
<5
A typical Current Consumption
APPLICATIONS
Portable Battery Powered Applications
Waveform Generators
Analog Processing
Instrumentation Applications
Programmable Amplifiers and Attenuators
Digitally-Controlled Calibration
Programmable Filters and Oscillators
Composite Video
Ultrasound
Gain, offset and Voltage Trimming
GENERAL DESCRIPTION
The AD5450/AD5451/AD5452/AD5453 are CMOS 8,
10, 12 and 14-bit Current Output digital-to-analog
converters respectively.
These devices operate from a +2.5 V to 5.5 V power sup-
ply, making them suited to battery powered applications
and many other applications.
These DACs utilize double buffered 3-wire serial interface
that is compatible with SPI
TM
, QSPI
TM
, MICROWIRE
TM
and most DSP interface standards.
On power-up, the internal shift register and latches are
filled with zeros and the DAC output is at zero scale.
As a result of manufacture on a CMOS sub micron
process, they offer excellent four quadrant multiplication
characteristics, with large signal multiplying bandwidths
of 10MHz.
FUNCTIONAL BLOCK DIAGRAM
The applied external reference input voltage (V
REF
)
determines the full scale output current. An integrated
feedback resistor (R
FB
) provides temperature tracking and
full scale voltage output when combined with an external
Current to Voltage precision amplifier.
The AD5450/AD5451/AD5452/AD5453 DACs are
available in small 8-lead TSOT & MSOP packages.
CONTROL LOGIC &
INPUT SHIFT REGISTER
SCLK
SYNC
AD5450/
AD5451/
AD5452/
AD5453
V
REF
IOUT1
R
FB
R
8/10/12/14
BIT
R-2R DAC
DAC REGISTER
SDIN
INPUT LATCH
V
DD
Power On
Reset
GND
2
REV. PrD
AD5450/AD5451/AD5452/AD5453SPECIFICATIONS
1
PRELIMINARY TECHNICAL DATA
Parameter
Min
Typ
M a x
Units
Conditions
STATIC PERFORMANCE
A D 5 4 5 0
Resolution
8
Bits
Relative Accuracy
0 . 2 5
L S B
Differential Nonlinearity
L S B
Guaranteed Monotonic
A D 5 4 5 1
Resolution
1 0
Bits
Relative Accuracy
0 . 2 5
L S B
Differential Nonlinearity
L S B
Guaranteed Monotonic
A D 5 4 5 2
Resolution
1 2
Bits
Relative Accuracy
0 . 5
L S B
Differential Nonlinearity
L S B
Guaranteed Monotonic
A D 5 4 5 3
Resolution
1 4
Bits
Relative Accuracy
2
L S B
Differential Nonlinearity
1
L S B
Guaranteed Monotonic
Total Unadjusted Error
2 . 4 4
m V
Gain Error
1 . 2 2
m V
Gain Error Temp Coefficient
2
5
ppm FSR/C
Output Leakage Current
1 0
n A
Data = 0000
H
, T
A
= 25C, I
OUT1
5 0
n A
Data = 0000
H
, I
OUT1
Output Voltage Compliance Range
1 . 2 3
V
REFERENCE INPUT
2
Reference Input Range
1 0
V
V
REF
Input Resistance
8
9 . 3
1 2
k
Input resistance TC = -50ppm/C
DIGITAL INPUTS
2
Input High Voltage, V
IH
2 . 0
V
V
DD
= 3.6 V to 5 V
1 . 7
V
V
DD
= 2.5 V to 3.6 V
Input Low Voltage, V
IL
0 . 8
V
V
DD
= 2.7 V to 5.5 V
0 . 7
V
V
DD
= 2.5 V to 2.7 V
Input Leakage Current, I
IL
1
A
Input Capacitance
1 0
p F
DYNAMIC PERFORMANCE
2
Reference Multiplying BW
10
MHz
V
REF
= +/-3.5V, DAC loaded all 1s
Output Voltage Settling Time
V
REF
= 10V, R
LOAD
= 100
, C
LOAD
= 15pF
DAC latch alternately loaded with 0s and 1s.
AD5450
1 0 0
n s
Measured to +/-16mV of FS
AD5451
1 1 0
n s
Measured to +/-4mV of FS
AD5452
1 6 0
n s
Measured to +/-1mV of FS
AD5453
1 8 0
n s
Measured to +/-1mV of FS
Digital Delay
2 0
4 0
n s
Interface delay time
10% to 90% Dettling Time
1 0
3 0
n s
Rise and Fall time, V
REF
= 10V, R
LOAD
=
100
,
C
LOAD
= 15pF
Digital to Analog Glitch Impulse
3
nV-s
1 LSB change around Major Carry, V
REF
=0V
Multiplying Feedthrough Error
DAC latch loaded with all 0s.
- 7 5
d B
Reference = 1MHz.
Reference = 10MHz.
Output Capacitance
IOUT1
5
p F
DAC Latches Loaded with all 0s
1 0
p F
DAC Latches Loaded with all 1s
IOUT2
1 0
p F
DAC Latches Loaded with all 0s
5
p F
DAC Latches Loaded with all 1s
Digital Feedthrough
0 . 1
nV-s
Feedthrough to DAC output with
CS high
and Alternate Loading of all 0s and all 1s.
(V
DD
= 2.5 V to 5.5 V, V
REF
= +10 V, I
OUT
x = O V. All specifications T
MIN
to T
MAX
unless otherwise noted. DC performance measured with
OP1177, AC performance with AD9631 unless otherwise noted.)
3
REV. PrD
AD5450/AD5451/AD5452/AD5453
PRELIMINARY TECHNICAL DATA
TIMING CHARACTERISTICS
1
Parameter
V
DD
= 4.5 V to 5.5 V
V
DD
= 2.5 V to 5.5 V Units
Conditions/Comments
f
SCLK
50
MHz max
Max Clock frequency
t
1
20
ns min
SCLK Cycle time
t
2
8
ns min
SCLK High Time
t
3
8
ns min
SCLK Low Time
t
4
8
ns min
SYNC falling edge to SCLK active edge setup time
t
5
5
ns min
Data Setup Time
t
6
4.5
ns min
Data Hold Time
t
7
5
ns min
SYNC rising edge to SCLK active edge
t
8
30
ns min
Minimum
SYNC high time
N O T E S
1
See Figures 1.
Temperature range is as follows: Y Version: 40C to +125C.
Guaranteed by design and characterisation, not subject to
production test.
All input signals are specified with tr =tf = 5ns (10% to 90% of V
DD
) and timed from a voltage level of (V
IL
+ V
IH
)/2.
Specifications subject to change without notice.
(V
REF
= +5 V, I
OUT
2 = O V. All specifications T
MIN
to T
MAX
unless otherwise noted.)
t1
DB15
DB0
t2
t3
t4
t5
t6
t8
SCLK
SYNC
DIN
t7
Parameter
Min
Typ
M a x
Units
Conditions
Total Harmonic Distortion
- 8 0
d B
V
REF
= 3.5 V pk-pk, All 1s loaded, f = 1kHz
Digital THD, Clock = 1MHz
50kHz f
OUT
7 5
d B
Output Noise Spectral Density
2 5
nV/
H z
@ 1kHz
SFDR performance (Wideband)
Update = 1MHz, V
REF
= 3.5V
Update = 1MHz
50kHz Fout
7 8
d B
20kHz Fout
7 8
d B
SFDR performance (NarrowBand)
Update = 1MHz, V
REF
= 3.5V
50kHz Fout
8 7
d B
20kHz Fout
8 7
d B
Intermodulation Distortion
7 8
d B
f1 = 20kHz, f2 = 25kHz, Update=1MHz,
V
REF
=3.5V
POWER REQUIREMENTS
Power Supply Range
2 . 5
5 . 5
V
I
DD
1
A
Logic Inputs = 0 V or V
DD
Power Supply Sensitivity
2
0.001
% / %
V
DD
= 5%
N O T E S
1
Temperature range is as follows: Y Version: 40C to +125C.
2
Guaranteed by design and characterisation, not subject to production test.
Specifications subject to change without notice.
Figure 1. Timing Diagram.
(V
DD
= 2.5 V to 5.5 V, V
REF
= +10 V, I
OUT
x = O V. All specifications T
MIN
to T
MAX
unless otherwise noted. DC performance measured with
OP1177, AC performance with AD9631 unless otherwise noted.)
4
REV. PrD
AD5450/AD5451/AD5452/AD5453
PRELIMINARY TECHNICAL DATA
ABSOLUTE MAXIMUM RATINGS
1, 2
(T
A
= +25C unless otherwise noted)
V
DD
to GND
0.3 V to +7 V
V
REF,
R
FB
to GND
12 V to +12 V
I
OUT
1 to GND
0.3 V to +7 V
Input Current to any pin except supplies
10 mA
Logic Inputs & Output
3
-0.3V to V
DD
+0.3 V
Operating Temperature Range
Industrial (Y Version)
40C to +125C
Storage Temperature Range
65C to +150C
Junction Temperature
+150C
8 lead MSOP
JA
Thermal Impedance
206C/W
8 lead TSOT
JA
Thermal Impedance
211C/W
Lead Temperature, Soldering (10seconds)
300C
IR Reflow, Peak Temperature (<20 seconds)
+235C
NOTES
1
Stresses above those listed under "Absolute Maximum Ratings" may cause permanent
damage to the device. This is a stress rating only and functional operation of the device
at these or any other conditions above those listed in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability. Only one absolute maximum rating may
be applied at any one time.
2
Transient currents of up to 100mA will not cause SCR latchup.
3
Overvoltages at SCLK,
SYNC, DIN, will be clamped by internal diodes. Current
should be limited to the maximum ratings given.
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the AD5450/AD5451/AD5452/AD5453 features proprietary ESD protection circuitry,
permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore,
proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
ORDERING GUIDE
Model
Resolution
INL
Temperature Range
Package Description Branding
Package Option
AD5450YUJ
8
0.25
-40
o
C to +125
o
C
T S O T
UJ-8
AD5451YUJ
10
0.25
-40
o
C to +125
o
C
T S O T
UJ-8
AD5452YUJ
12
0.5
-40
o
C to +125
o
C
T S O T
UJ-8
AD5452YRM 12
0.5
-40
o
C to +125
o
C
M S O P
RM-8
AD5453YUJ
14
2
-40
o
C to +125
o
C
T S O T
UJ-8
AD5453YRM 14
2
-40
o
C to +125
o
C
M S O P
RM-8
AD5450/AD5451/AD5452/AD5453
5
REV. PrD
PRELIMINARY TECHNICAL DATA
PIN FUNCTION DESCRIPTION
MSOP
TSOT
Mnemonic Function
1
8
I
OUT
1
DAC Current Output.
2
7
G N D
Ground Pin.
3
6
SCLK
Serial Clock Input. By default, data is clocked into the input shift register on the
falling edge of the serial clock input. Alternatively, by means of the serial control
bits, the device may be configured such that data is clocked into the shift register on
the rising edge of SCLK.
4
5
S D I N
Serial Data Input. Data is clocked into the 16-bit input register on the active edge of
the serial clock input. By default, on power up, data is clocked into the shift register
on the falling edge of SCLK. The control bits allow the user to change the active
edge to rising edge.
5
4
S Y N C
Active Low Control Input. This is the frame synchronization signal for the input
data. Data is loaded to the shift register on the active edge of the
following clocks.
6
3
V
D D
Positive power supply input. These parts can operate from a supply of +2.5 V to
+5.5 V.
7
2
V
REF
DAC reference voltage input pin.
8
1
R
F B
DAC feedback resistor pin. Establish voltage output for the DAC by connecting to
external amplifier output.
PIN CONFIGURATION
AD5452/
AD5453
(Not to Scale)
IOUT1
GND
SCLK
SDIN
1
2
3
4
5
6
7
8 RFB
VREF
VDD
SYNC
AD5450/
AD5451/
AD5452/
AD5453
(Not to Scale)
IOUT1
GND
SCLK
SDIN
1
2
3
4
5
6
7
8
RFB
VREF
VDD
SYNC
MSOP (RM-8)
TSOT (UJ-8)
6
REV. PrD
AD5450/AD5451/AD5452/AD5453
PRELIMINARY TECHNICAL DATA
TERMINOLOGY
Relative Accuracy
Relative accuracy or endpoint nonlinearity is a measure of the maximum deviation from a straight line passing through the
endpoints of the DAC transfer function. It is measured after adjusting for zero and full scale and is normally expressed in
LSBs or as a percentage of full scale reading.
Differential Nonlinearity
Differential nonlinearity is the difference between the measured change and the ideal 1 LSB change between any two adja-
cent codes. A specified differential nonlinearity of -1 LSB max over the operating temperature range ensures monotonic-
ity.
Gain Error
Gain error or full-scale error is a measure of the output error between an ideal DAC and the actual device output. For
these DACs, ideal maximum output is V
REF
1 LSB. Gain error of the DACs is adjustable to zero with external resis-
tance.
Output Leakage Current
Output leakage current is current which flows in the DAC ladder switches when these are turned off. For the I
OUT1
termi-
nal, it can be measured by loading all 0s to the DAC and measuring the I
OUT1
current. Minimum current will flow in the
I
OUT2
line when the DAC is loaded with all 1s
Output Capacitance
Capacitance from I
OUT1
or I
OUT2
to AGND.
Output Current Settling Time
This is the amount of time it takes for the output to settle to a specified level for a full scale input change. For these de-
vices, it is specifed with a 100
resistor to ground. The settling time specification includes the digital delay from SYNC
rising edge to the full scale output change.
Digital to Analog Glitch lmpulse
The amount of charge injected from the digital inputs to the analog output when the inputs change state. This is normally
specified as the area of the glitch in either pA-secs or nV-secs depending upon whether the glitch is measured as a current
or voltage signal.
Digital Feedthrough
When the device is not selected, high frequency logic activity on the device digital inputs may be capacitivelly coupled
through the device to show up as noise on the I
OUT
pins and subsequently into the following circuitry. This noise is digital
feedthrough.
Multiplying Feedthrough Error
This is the error due to capacitive feedthrough from the DAC reference input to the DAC I
OUT1
terminal, when all 0s are
loaded to the DAC.
Total Harmonic Distortion (THD)
The DAC is driven by an ac reference. The ratio of the rms sum of the harmonics of the DAC output to the fundamental
value is the THD. Usually only the lower order harmonices are included, such as second to fifth.
THD
= 20log
(V
2
2
+ V
3
2
+ V
4
2
+ V
5
2
)
V
1
Digital Intermodulation Distortion
Second order intermodulation (IMD) measurements are the relative magnitudes of the fa and fb tones generated digitally
by the DAC and the second order products at 2fa-fb and 2fb-fa.
Compliance Voltage Range
The maximum range of (output) terminal voltage for which the device will provide the specified characteristics.
Spurious-Free Dynamic Range(SFDR)
It is the usable dynamic range of a DAC before spurious noise interferes or distorts the fundamental signal. SFDR is the
measure of difference in amplitude between the fundamental and the largest harmonically or nonharmonically related spur
from dc to full Nyquist bandwidth (half the DAC sampling rate or fs/2). Narrow band SFDR is a measure of SFDR over
an arbitrary window size, in this case 50% of hte fundamental. Digital SFDR is a measure of the usable dymanic range of
the DAC when the signal is a digitally generated sine wave.
AD5450/AD5451/AD5452/AD5453
7
REV. PrD
PRELIMINARY TECHNICAL DATA
Typical Performance Characteristics
TPC 1. INL vs. Code (8-Bit DAC)
TPC 4. INL vs. Code (14-Bit DAC)
TPC 7. DNL vs. Code (12-Bit DAC)
TPC 2. INL vs. Code (10-Bit DAC)
TPC 5. DNL vs. Code (8-Bit DAC)
TPC 8. DNL vs. Code (14-Bit DAC)
TPC 3. INL vs. Code (12-Bit DAC)
TPC 6. DNL vs. Code (10-Bit DAC)
TPC 9. INL vs Reference Voltage
8
REV. PrD
AD5450/AD5451/AD5452/AD5453
PRELIMINARY TECHNICAL DATA
TPC10. DNL vs. Reference Voltage
TPC 13. DNL vs Code - Biased Mode
TPC 16. TUE vs Code
TPC11. Linearity Errors vs. V
DD
TPC 14. INL Error vs. Reference -
Biased Mode
TPC 17. Supply Current vs. Clock Freq
TPC12. INL vs Code - Biased Mode
TPC 15. DNL Error vs. Reference -
Biased Mode
TPC 18. Logic Threshold vs Supply
Voltage
AD5450/AD5451/AD5452/AD5453
9
REV. PrD
PRELIMINARY TECHNICAL DATA
TPC 19. Supply Current vs Logic Input
Voltage
TPC 22. Reference Multiplying
Bandwidth - small signal
TPC 25. Midscale Transition and
Digital Feedthrough
TPC 20. Reference Multiplying
Bandwidth - small signal
TPC 23. Reference Multiplying
Bandwidth - large signal
TPC 26. Power Supply Rejection vs
Frequency
TPC 21. Reference Multiplying
Bandwidth - large signal
TPC 24. Settling Time
TPC 27. Noise Spectral Density vs
Frequency
10
REV. PrD
AD5450/AD5451/AD5452/AD5453
PRELIMINARY TECHNICAL DATA
TPC 28. TBD
TPC 29. TBD
TPC 30. TBD
AD5450/AD5451/AD5452/AD5453
11
REV. PrD
PRELIMINARY TECHNICAL DATA
GENERAL DESCRIPTION
DAC SECTION
The AD5450, AD5451, AD5452 and AD5453 are 8, 10,
12 and 14 bit current output DACs consisting of a
segmented (4-Bits) inverting R-2R ladder configuration.
The feedback resistor R
FB
has a value of R. The value of R
is typically 9.3k
(minimum 8k
and maximum 12k
).
If I
OUT1
is kept at the same potential as GND, a constant
current flows in each ladder leg, regardless of digital input
code. Therefore, the input resistance presented at V
REF
is
always constant and nominally of value R. The DAC
output (I
OUT
) is code-dependent, producing various
resistances and capacitances. External amplifier choice
should take into account the variation in impedance
generated by the DAC on the amplifiers inverting input
node.
Access is provided to the V
REF
, R
FB
, and I
OUT1
terminals
of the DAC, making the device extremely versatile and
allowing it to be configured in several different operating
modes, for example, to provide a unipolar output and in
four quadrant multiplication in bipolar mode. Note that a
matching switch is used in series with the internal R
FB
feedback resistor. If users attempt to measure R
FB
, power
must be applied to V
DD
to achieve continuity.
SERIAL INTERFACE
The AD5450/AD5451/AD5452/AD5453 have an easy to
use 3-wire interface which is compatible with SPI/QSPI/
MicroWire and DSP interface standards. Data is written
to the device in 16 bit words. This 16-bit word consists of
2 control bits and either 8, 10 12, or 14 data bits as shown
in Figure 2. The AD5453 uses all 14 bits of DAC data.
The AD5452 uses twelve bits and ignores the two LSBs,
similarly the AD5451 uses ten bits and ignores the four
LSBs, while the AD5450 uses eight bits and ignores the
last six bits.
DAC Control Bits C1, C0
Control bits C1 and C0 the user to load and update the
new DAC code and to change the active clock edge. By
default the shift register clocks data in on the falling edge,
this can be changed via the control bits. In this case, the
DAC core is inoperative until the next data frame. A
power cycle resets this back to default condition.
On chip power on reset circuitry ensures the device
powers on with zeroscale loaded to the DAC register and
I
OUT
line.
TABLE III. DAC CONTROL BITS
C1
C0
Funtion Implemented
0
0
Load and Update(Power On Default)
0
1
Reserved
1
0
Reserved
1
1
Clock Data to shift register On Rising Edge
SYNC
SYNC
SYNC
SYNC
SYNC Function
SYNC is an edge-triggered input that acts as a frame
synchronization signal and chip enable. Data can only be
transferred into the device while
SYNC is low. To start
the serial data transfer,
SYNC should be taken low ob-
serving the minimum
SYNC falling to SCLK falling
edge setup time, t
4
.
After the falling edge of the 16th SCLK pulse, bring
SYNC high to transfer data from the input shift register to
the DAC register.
Figure 2b. AD5451 10 bit Input Shift Register Contents
Figure 2c. AD5452 12 bit Input Shift Register Contents
DB0 (LSB)
DB15 (MSB)
DATA BITS
C1
C0
X
X
X
X
CONTROL BITS
DB7 DB6 DB5 DB4
DB3 DB2
DB0
DB1
X
X
Figure 2a. AD5450 8 bit Input Shift Register Contents
DB0 (LSB)
DB15 (MSB)
X
X
DATA BITS
CONTROL BITS
DB5 DB4
DB3 DB2
DB0
DB1
C1
C0
DB7 DB6
DB8
DB9
X
X
DB0 (LSB)
DB15 (MSB)
DATA BITS
CONTROL BITS
DB7 DB6 DB5 DB4
DB3 DB2
DB0
DB1
C1
C0
DB11 DB10
DB8
DB9
X
X
DB0 (LSB)
DB15 (MSB)
DATA BITS
CONTROL BITS
DB9 DB8 DB7 DB6
DB5 DB4
DB2
DB3
C1
C0
DB13 DB12
DB10
DB11
DB0
DB1
Figure 2c. AD5453 14 bit Input Shift Register Contents
12
REV. PrD
AD5450/AD5451/AD5452/AD5453
PRELIMINARY TECHNICAL DATA
CIRCUIT OPERATION
Unipolar Mode
Using a single op amp, these devices can easily be
configured to provide 2 quadrant multiplying operation or
a unipolar output voltage swing as shown in Figure 3.
When an output amplifier is connected in unipolar mode,
the output voltage is given by:
V
OUT
= -D/2
n
x V
REF
Where D is the fractional representation of the digital
word loaded to the DAC, and n is the number of bits.
D = 0 to 255 (8-Bit AD5450)
= 0 to 1023 (10-Bit AD5451)
= 0 to 4095 (12-Bit AD5452)
= 0 to 16383 (14-Bit AD5453)
Note that the output voltage polarity is opposite to the
V
REF
polarity for dc reference voltages.
V
OUT
= 0 to -VREF
SCLK SDIN
V
DD
GND
V
REF
SYNC
IOUT1
RFB
V
DD
V
REF
uController
AGND
AD5450/1/2/3
NOTES:
1
R1 AND R2 USED ONLY IF GAIN ADJUSTMENT IS REQUIRED.
2
C1 PHASE COMPENSATION (1pF - 5pF) MAY BE REQUIRED
IF A1 IS A HIGH SPEED AMPLIFIER.
R
1
R
2
C
1
A1
Figure 3. Unipolar Operation
These DACs are designed to operate with either negative
or positive reference voltages. The V
DD
power pin is only
used by the internal digital logic to drive the DAC
switches' ON and OFF states.
These DACs are also designed to accommodate ac refer-
ence input signals in the range of -10V to +10V.
With a fixed 10 V reference, the circuit shown above will
give an unipolar 0V to -10V output voltage swing. When
V
IN
is an ac signal, the circuit performs two-quadrant
multiplication.
The following table shows the relationship between digital
code and expected output voltage for unipolar operation.
(AD5450, 8-Bit device).
Table I. Unipolar Code Table
Digital Input
Analog Output (V)
1111 1111
-V
REF
(255/256)
1000 0000
-V
REF
(128/256) = -V
REF
/2
0000 0001
-V
REF
(1/256)
0000 0000
-V
REF
(0/256) = 0
Bipolar Operation
In some applications, it may be necessary to generate full
4-Quadrant multplying operation or a bipolar output
swing. This can be easily accomplished by using another
external amplifier and some external resistors as shown in
Figure 4. In this circuit, the second amplifier A2 provides
a gain of 2. Biasing the external amplifier with an offset
from the reference voltage results in full 4-quadrant
multiplying operation. The transfer function of this circuit
shows that both negative and positive output voltages are
created as the input data (D) is incremented from code
zero (V
OUT
= - V
REF
) to midscale (V
OUT
- 0V ) to full
scale (V
OUT
= + V
REF
).
V
OUT
= (V
REF
x D /
2
n-1
)
-
V
REF
Where D is the fractional representation of the digital
word loaded to the DAC and n is the resolution of the
DAC.
D = 0 to 255 (8-Bit AD5450)
= 0 to 1023 (10-Bit AD5451)
= 0 to 4095 (12-Bit AD5452)
= 0 to 16383 (14-Bit AD5453)
When V
IN
is an ac signal, the circuit performs four-
quadrant multiplication.
Table II. shows the relationship between digital code and
the expected output voltage for bipolar operation
(AD5450, 8-Bit device).
Figure 4. Bipolar Operation (4 Quadrant Multiplication)
V
OUT
SCLK SDIN
V
DD
V
REF
10V
SYNC
GND
IOUT1
RFB
V
DD
V
REF
uController
NOTES:
1
R1 AND R2 ARE USED ONLY IF GAIN ADJUSTMENT IS REQUIRED.
ADJUST R1 FOR V
OUT
= 0V WITH CODE 10000000 LOADED TO DAC.
2
MATCHING AND TRACKING IS ESSENTIAL FOR RESISTOR PAIRS
R3 AND R4.
3
C1 PHASE COMPENSATION (1pF-5pF) MAY BE REQUIRED
IF A1/A2 IS A HIGH SPEED AMPLIFIER.
R4
10k
R5
20k
AGND
= -VREF to +VREF
R3
20k
AD5450/1/2/3
R1
R2
C1
A1
A2
AD5450/AD5451/AD5452/AD5453
13
REV. PrD
PRELIMINARY TECHNICAL DATA
Table II. Bipolar Code Table
Digital Input
Analog Output (V)
1111 1111
+V
REF
(127/128)
1000 0000
0
0000 0001
-V
REF
(127/128)
0000 0000
-V
REF
(128/128)
Stability
In the I-to-V configuration, the I
OUT
of the DAC and the
inverting node of the op amp must be connected as close
as possible, and proper PCB layout techniques must be
employed. Since every code change corresponds to a step
function, gain peaking may occur if the op amp has
limited GBP and there is excessive parasitic capacitance at
the inverting node. This parasitic capacitance introduces a
pole into the open loop response which can cause ringing
or instability in the closed loop applications circuit.
An optional compensation capacitor, C1 can be added in
parallel with R
FB
for stability as shown in figures 3 and 4.
Too small a value of C1 can produce ringing at the
output, while too large a value can adversely affect the
settling time. C1 should be found empirically but 1-2pF is
generally adequate for the compensation.
SINGLE SUPPLY APPLICATIONS
Voltage Switching Mode of Operation
Figure 5 shows these DACs operating in the voltage-
switching mode. The reference voltage, V
IN
is applied to
the I
OUT1
pin, I
OUT2
is connected to AGND and the
output voltage is available at the V
REF
terminal. In this
configuration, a positive reference voltage results in a
positive output voltage making single supply operation
possible. The output from the DAC is voltage at a
constant impedance (the DAC ladder resistance). Thus an
op-amp is necessary to buffer the output voltage. The
reference input no longer sees a constant input impedance,
but one that varies with code. So, the voltage input should
be driven from a low impedance source.
V
OUT
V
DD
GND
V
IN
IOUT1
RFB
V
DD
V
REF
NOTES:
1
ADDITIONAL PINS OMITTED FOR CLARITY
2
C1 PHASE COMPENSATION (1pF-5pF) MAY BE REQUIRED
IF A1 IS A HIGH SPEED AMPLIFIER.
R
2
R
1
Figure 5. Single Supply Voltage Switching Mode Operation.
It is important to note that V
IN
is limited to low voltages
because the switches in the DAC ladder no longer have
the same source-drain drive voltage. As a result their on
resistance differs and this degrades the integral linearity of
the DAC. Also, V
IN
must not go negative by more than
0.3V or an internal diode will turn on, exceeding the max
ratings of the device. In this type of application, the full
range of multiplying capability of the DAC is lost.
POSITIVE OUTPUT VOLTAGE
Note that the output voltage polarity is opposite to the
V
REF
polarity for dc reference voltages. In order to achieve
a positive voltage output, an applied negative reference to
the input of the DAC is preferred over the output
inversion through an inverting amplifier because of the
resistors tolerance errors. To generate a negative
reference, the reference can be level shifted by an op amp
such that the V
OUT
and GND pins of the reference
become the virtual ground and -2.5V respectively as
shown in Figure 6.
V
OUT = 0 to +2.5V
V
DD = 5V
GND
IOUT2
IOUT1
RFB
V
DD
V
REF
C
1
NOTES:
1
ADDITIONAL PINS OMITTED FOR CLARITY
2
C1 PHASE COMPENSATION (1pF-5pF) MAY BE REQUIRED
IF A1 IS A HIGH SPEED AMPLIFIER.
GND
VIN
VOUT
ADR03
+
5V
-
5V
1/2 AD8552
1/2 AD8552
-2.5V
Figure 6. Positive Voltage output with minimum of
components.
ADDING GAIN
In applications where the output voltage is required to be
greater than V
IN
, gain can be added with an additional
external amplifier or it can also be achieved in a single
stage. It is important to take into consideration the effect
of temperature coefficients of the thin film resistors of the
DAC. Simply placing a resistor in series with the RFB
resistor will causing mis-matches in the Temperature
coefficients resulting in larger gain temperature coefficient
errors. Instead, the circuit of Figure 7 is a recommended
method of increasing the gain of the circuit. R1, R2 and
R3 should all have similar temperature coefficients, but
they need not match the temperature coefficients of the
DAC. This approach is recommended in circuits where
gains of great than 1 are required.
14
REV. PrD
AD5450/AD5451/AD5452/AD5453
PRELIMINARY TECHNICAL DATA
V
OUT
V
DD
GND
IOUT2
IOUT1
RFB
V
DD
V
REF
C
1
NOTES:
1
ADDITIONAL PINS OMITTED FOR CLARITY
2
C1 PHASE COMPENSATION (1pF-5pF) MAY BE REQUIRED
IF A1 IS A HIGH SPEED AMPLIFIER.
R
3
R
2
R
2
V
IN
R1 = R2R3
R2 + R3
GAIN = R2 + R3
R2
Figure 7. Increasing Gain of Current Output DAC
USED AS A 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
FB
is used as the input resistor as shown in Figure 8,
then the output voltage is inversely proportional to the
digital input fraction D. For D = 1-2
n
the output voltage
is
V
OUT
= -V
IN
/D = -V
IN
/(1-2
-n
)
V
OUT
V
DD
GND
V
IN
IOUT1
RFB
V
DD
V
REF
NOTES:
1
ADDITIONAL PINS OMITTED FOR CLARITY
Figure 8. Current Steering DAC used as a divider or
Programmable Gain Element
As D is reduced, the output voltage increases. For small
values of the digital fraction D, it is important to ensure
that the arnplifier does not saturate and also that the
required accuracy is met. For example, an eight bit DAC
driven with the binary code 10H (00010000), i.e., 16
decimal, in the circuit of Figure 8 should cause the output
voltage to be sixteen times V
IN
. However, if the DAC has
a linearity specification of +/- 0.5LSB then D
can in fact have the weight anywhere in the range 15.5/256
to 16.5/256 so that the possible output voltage will be in
the range 15.5V
IN
to 16.5V
IN
--an error of + 3% even
though the DAC itself has a 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. Since only a fraction D of the
current into the V
REF
terminal is routed to the I
OUT1
ter-
minal, the output voltage has to change as follows:
Output Error Voltage Due to Dac Leakage
= (Leakage x R)/D
where R is the DAC resistance at the V
REF
terminal. For a
DAC leakage current of 10nA, R = 10 kilohm and a gain
(i.e., 1/D) of 16 the error voltage is 1.6mV.
REFERENCE SELECTION
When selecting a reference for use with the AD5426 series
of current output DACs, pay attention to the references
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
1LSB over the temperature range 0-50
o
C dictates that the
maximum system drift with temperature should be less than
78ppm/
o
C. A 14-Bit system with the same temperature
range to overall specification within 2LSBs requires a
maximum drift of 10ppm/
o
C. By choosing a precision
reference with low output temperature coefficient this
error source can be minimized. Table IV. suggests some
of the suitable 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 (due to the code dependent
output resistance of the DAC) 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 could cause the
DAC to be non-monotonic.
The input bias curent 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, 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, 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.
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
AD5450/AD5451/AD5452/AD5453
15
REV. PrD
PRELIMINARY TECHNICAL DATA
at the V
REF
node (voltage output node in this application)
of the DAC. This is done by using low inputs capacitance
buffer amplifiers and careful board design.
Most single supply circuits include ground as part of the
analog signal range, which in turns requires an
ampliferthat can handle rail to rail signals, there is a large
range of single supply amplifiers available from Analog
Devices.
PCB LAYOUT AND POWER SUPPLY DECOUPLING
In any circuit where accuracy is important, careful
consideration of the power supply and ground return
layout helps to ensure the rated performance. The printed
circuit board on which the AD5426/AD5432/AD5443 is
mounted should be designed so that the analog and digital
sections are separated, and cofined to certain areas of the
board. If the DAC is in a system where multiple devices
require an AGND-to-DGND connection, the connection
should be made at one point only. The star ground point
should be established as close as possible to the device.
These DACs should have ample supply bypassing of 10
F in parallel with 0.1 F on the supply located as close
to the package as possible, ideally right up against the
device. The 0.1 F capacitor should have low Effective
Series Resistance (ESR) and Effective Series Inductance
(ESI), like the common ceramic types that provide a low
impedance path to ground at high frequencies, to handle
transient currents due to internal logic switching. Low
ESR 1 F to 10 F tantalum or electrolytic capacitors
should also be applied at the supplies to minimize
transient disturbance and filter out low frequency ripple.
Fast switching signals such as clocks should be shielded
with digital ground to avoid radiating noise to other parts
of the board, and should never be run near the reference
inputs.
Avoid crossover of digital and analog signals. Traces on
opposite sides of the board should run at right angles to
each other. This reduces the effects of feedthrough
through the board. A microstrip technique is by far the
best, but not always possible with a doublesided board. In
this technique, the component side of the board is
dedicated to ground plane while signal traces are placed
on the solder side.
It is good practice to employ compact, minimum lead
length PCB layout design. Leads to the input should be as
short as possible to minimize IR drops and stray
inductance.
The PCB metal traces between V
REF
and R
FB
should also
be matched to minimize gain error. To maximize on high
frequency performance, the I-to-V amplifier should be
located as close to the device as possible.
Table IV. Listing of suitable ADI Precision References recommended for use with AD5450/1/2/3 DACs.
Reference
Output Voltage
Initial Tolerance
Temperature Drift
0.1Hz to 10Hz noise
Package
ADR01
10 V
0.1%
3ppm/
o
C
20
Vp-p
SC70, TSOT, SOIC
ADR02
5 V
0.1%
3ppm/
o
C
10
Vp-p
SC70, TSOT, SOIC
ADR03
2.5 V
0.2%
3ppm/
o
C
10
Vp-p
SC70, TSOT, SOIC
ADR425
5 V
0.04%
3ppm/
o
C
3.4
Vp-p
MSOP, SOIC
Table V. Listing of some precision ADI Op Amps suitable for use with AD5450/1/2/3 DACs.
Part #
Max Supply Voltage V
V
OS
( m a x )
V I
B
(max) nA
GBP MHz
Slew Rate V/
s
t
SETTLE
with AD5453
OP97
20
25
0.1
0.9
0.2
OP1177
18
60
2
1.3
0.7
AD8551 6
5
0.05
1.5
0.4
Table VI. Listing of some High Speed ADI Op Amps suitable for use with AD5450/1/2/3 DACs.
Part #
Max Supply Voltage V
BW @ A
CL
MHz
Slew Rate V/
s
t
SETTLE
with AD5453
V
OS
( m a x )
V I
B
(max) nA
AD8065 12
145
180
1500
0.01
AD8021 12
200
100
1000
1000
AD8038 5
350
425
3000
0.75
AD9631 5
320
1300
10000
7000
AD5450/AD5451/AD5452/AD5453
16
REV. PrD
PRELIMINARY TECHNICAL DATA
8 Lead TSOT
(UJ-8)
1
2
3
4
8
7
6
5
PIN 1
1.95 BSC
0.65 BSC
SEATING
PLANE
2.90 BSC
2.80 BSC
1.60 BSC
1.00
0.90
0.70
0.10 MAX
1.10 MAX
0.20
0.08
0.38
0.22
0.60
0.45
0.30
8
4
0
O
O
O
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8 Lead MSOP
(RM-8)
8
5
4
1
0.122 (3.10)
0.114 (2.90)
0.199 (5.05)
0.187 (4.75)
PIN 1
0.0256 (0.65) BSC
0.122 (3.10)
0.114 (2.90)
SEATING
PLANE
0.006 (0.15)
0.002 (0.05)
0.018 (0.46)
0.008 (0.20)
0.043 (1.09)
0.037 (0.94)
0.120 (3.05)
0.112 (2.84)
0.011 (0.28)
0.003 (0.08)
0.028 (0.71)
0.016 (0.41)
33
27
0.120 (3.05)
0.112 (2.84)
Overview of AD54xx devices
Part #
Resolution #DACs
INL
t
S
Interface
Package
Features
AD5403
1
8
2
0.25
20ns
Parallel
CP-40
10 MHz BW, 17 ns
CS Pulse Width, 4-
Quadrant Multiplying Resistors
AD5410
1
8
1
0.25
20ns
Serial
R U - 1 6
10 MHz BW, 50 MHz Serial, 4- Quadrant
Multiplying Resistors
AD5413
1
8
2
0.25
20ns
Serial
R U - 2 4
10 MHz BW, 50 MHz Serial, 4- Quadrant
Multiplying Resistors
AD5424
8
1
0.25
60ns
Parallel
RU-16, CP-20 10 MHz BW, 17 ns
CS Pulse Width
AD5425
8
1
0.25
100ns
Serial
R M - 1 0
Byte Load,10 MHz BW, 50 MHz Serial
AD5426
8
1
0.25
100ns
Serial
R M - 1 0
10 MHz BW, 50 MHz Serial
AD5428
2
8
2
0.25
60ns
Parallel
R U - 2 0
10 MHz BW, 17 ns
CS Pulse Width
AD5429
2
8
2
0.25
100ns
Serial
R U - 1 0
10 MHz BW, 50 MHz Serial
AD5450
2
8
1
0.25
100ns
Serial
R J - 8
10 MHz BW, 50 MHz Serial
AD5404
1
1 0
2
0.5
25ns
Parallel
CP-40
10 MHz BW, 17 ns
CS Pulse Width, 4-
Quadrant Multiplying Resistors
AD5411
1
1 0
1
0.5
25ns
Serial
R U - 1 6
10 MHz BW, 50 MHz Serial, 4- Quadrant
Multiplying Resistors
AD5414
1
1 0
2
0.5
25ns
Serial
R U - 2 4
10 MHz BW, 50 MHz Serial, 4- Quadrant
Multiplying Resistors
AD5432
1 0
1
0.5
110ns
Serial
R M - 1 0
10 MHz BW, 50 MHz Serial
AD5433
1 0
1
0.5
70ns
Parallel
RU-20, CP-20 10 MHz BW, 17 ns
CS Pulse Width
AD5439
2
1 0
2
0.5
110ns
Serial
R U - 1 6
10 MHz BW, 50 MHz Serial
AD5440
2
1 0
2
0.5
70ns
Parallel
R U - 2 4
10 MHz BW, 17 ns
CS Pulse Width
AD5451
2
1 0
1
0.25
110ns
Serial
R J - 8
10 MHz BW, 50 MHz Serial
AD5405
2
1 2
2
1
120ns
Parallel
CP-40
10 MHz BW, 17 ns
CS Pulse Width, 4-
Quadrant Multiplying Resistors
AD5412
1
1 2
1
1
160ns
Serial
R U - 1 6
10 MHz BW, 50 MHz Serial, 4- Quadrant
Multiplying Resistors
AD5415
2
1 2
2
1
160ns
Serial
R U - 2 4
10 MHz BW, 50 MHz Serial, 4- Quadrant
Multiplying Resistors
AD5443
1 2
1
1
160ns
Serial
R M - 1 0
10 MHz BW, 50 MHz Serial
AD5445
1 2
1
1
120ns
Parallel
RU-20, CP-20 10 MHz BW, 17 ns
CS Pulse Width
AD5447
2
1 2
2
1
120ns
Parallel
R U - 2 4
10 MHz BW, 17 ns
CS Pulse Width
AD5449
2
1 2
2
1
160ns
Serial
R U - 1 6
10 MHz BW, 50 MHz Serial
AD5452
2
1 2
1
0.5
160ns
Serial
RJ-8, RM-8
10 MHz BW, 50 MHz Serial
AD5453
2
1 4
1
2
180ns
Serial
RJ-8, RM-8
10 MHz BW, 50 MHz Serial
1
Future parts, contact factory for availability
2
In development, contact factory for availability
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