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MOS
16-Bit Voltage Output DAC
AD7846
FEATURES
16-bit monotonicity over temperature
±2 LSBs integral linearity error
Microprocessor compatible with readback capability
Unipolar or bipolar output
Multiplying capability
Low power (100 mW typical)
V
REF+
7
FUNCTIONAL BLOCK DIAGRAM
V
CC
21
V
DD
4
R
16
SEGMENT
SWITCH
MATRIX
AD7846
A2
R
R
A3
6
R
IN
R
5
V
OUT
12-BIT DAC
A1
12
23
R
V
REF–
8
CS
R/W
LDAC
CLR
08490-001
DAC LATCH
4
12
I/O LATCH
24
9
10
3
20
CONTROL
LOGIC
22
25
V
SS
DB15 DB0
DGND
Figure 1.
GENERAL DESCRIPTION
The AD7846 is a 16-bit DAC constructed with the Analog Devices,
Inc., LC
2
MOS process. It has V
REF+
and V
REF−
reference inputs
and an on-chip output amplifier. These can be configured to
give a unipolar output range (0 V to +5 V, 0 V to +10 V) or
bipolar output ranges (±5 V, ±10 V).
The DAC uses a segmented architecture. The four MSBs in the
DAC latch select one of the segments in a 16-resistor string.
Both taps of the segment are buffered by amplifiers and fed to a
12-bit DAC, which provides a further 12 bits of resolution. This
architecture ensures 16-bit monotonicity. Excellent integral
linearity results from tight matching between the input offset
voltages of the two buffer amplifiers.
In addition to the excellent accuracy specifications, the AD7846
also offers a comprehensive microprocessor interface. There are
16 data I/O pins, plus control lines (CS, R/W, LDAC and CLR).
R/W and CS allow writing to and reading from the I/O latch.
This is the readback function, which is useful in ATE applications.
LDAC allows simultaneous updating of DACs in a multi-DAC
system and the CLR line will reset the contents of the DAC latch
to 00…000 or 10…000 depending on the state of R/W. This
means that the DAC output can be reset to 0 V in both the
unipolar and bipolar configurations.
The AD7846 is available in 28-lead plastic, ceramic, and PLCC
packages.
PRODUCT HIGHLIGHTS
1.
16-Bit Monotonicity
The guaranteed 16-bit monotonicity over temperature
makes the AD7846 ideal for closed-loop applications.
Readback
The ability to read back the DAC register contents
minimizes software routines when the AD7846 is used in
ATE systems.
Power Dissipation
Power dissipation of 100 mW makes the AD7846 the
lowest power, high accuracy DAC on the market.
2.
3.
Rev. G
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 that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2000–2010 Analog Devices, Inc. All rights reserved.
AD7846
TABLE OF CONTENTS
Features .............................................................................................. 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Product Highlights ........................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
AC Performance Characteristics ................................................ 4
Timing Characteristics ................................................................ 5
Absolute Maximum Ratings............................................................ 6
ESD Caution .................................................................................. 6
Pin Configurations and Function Descriptions ........................... 7
Typical Performance Characteristics ............................................. 8
Terminology .................................................................................... 10
Circuit Description ......................................................................... 11
Digital Section............................................................................. 11
Digital-to-Analog Conversion .................................................. 11
Output Stage................................................................................ 12
Unipolar Binary Operation ........................................................... 13
Bipolar Operation ........................................................................... 14
Multiplying Operation ............................................................... 14
Position Measurement Application.............................................. 15
Microprocessor Interfacing ........................................................... 16
AD7846-to-8086 Interface ........................................................ 16
AD7846-to-MC68000 Interface ............................................... 16
Digital Feedthrough ....................................................................... 17
Application Hints ........................................................................... 18
Noise ............................................................................................ 18
Grounding ................................................................................... 18
Printed Circuit Board Layout ................................................... 18
Outline Dimensions ....................................................................... 20
Ordering Guide .......................................................................... 22
REVISION HISTORY
4/10—Rev. F to Rev. G
Change to Figure 1 ........................................................................... 1
12/09—Rev. E to Rev. F
Updated Format .................................................................. Universal
Changes to Table 4 ............................................................................ 6
Deleted Other Output Voltage Ranges Section ............................ 9
Deleted Figure 20 and Table 5; Renumbered Sequentially ......... 9
Deleted Test Application Section and Figure 21 ........................ 10
Deleted Figure 29 to Figure 31 ...................................................... 14
Changes to Printed Circuit Board Layout Section ..................... 18
Updated Outline Dimensions ....................................................... 20
Changes to Ordering Guide .......................................................... 22
Rev. G | Page 2 of 24
AD7846
SPECIFICATIONS
V
DD
= +14.25 V to +15.75 V; V
SS
= −14.25 V to –15.75 V; V
CC
= +4.75 V to +5.25 V. V
OUT
loaded with 2 kΩ, 1000 pF to 0 V; V
REF+
= +5 V;
R
IN
connected to 0 V. All specifications T
MIN
to T
MAX
, unless otherwise noted.
Table 1.
Parameter
1
RESOLUTION
UNIPOLAR OUTPUT
Relative Accuracy at +25°C
T
MIN
to T
MAX
Differential Nonlinearity Error
Gain Error at +25°C
T
MIN
to T
MAX
Offset Error at +25°C
T
MIN
to T
MAX
Gain TC
2
Offset TC
2
BIPOLAR OUTPUT
Relative Accuracy at +25°C
T
MIN
to T
MAX
Differential Nonlinearity Error
Gain Error at +25°C
T
MIN
to T
MAX
Offset Error at +25°C
T
MIN
to T
MAX
Bipolar Zero Error at +25°C
T
MIN
to T
MAX
Gain TC
2
Offset TC
2
Bipolar Zero TC
2
REFERENCE INPUT
Input Resistance
V
REF+
Range
V
REF−
Range
OUTPUT CHARACTERISTICS
Output Voltage Swing
Resistive Load
Capacitive Load
Output Resistance
Short Circuit Current
DIGITAL INPUTS
V
IH
(Input High Voltage)
V
IL
(Input Low Voltage)
I
IN
(Input Current)
C
IN
(Input Capacitance)
2
J, A Versions
16
±12
±16
±1
±12
±16
±12
±16
±1
±1
±6
±8
±1
±6
±16
±6
±16
±6
±12
±1
±1
±1
20
40
V
SS
+ 6 to
V
DD
− 6
V
SS
+ 6 to
V
DD
− 6
V
SS
+ 4 to
V
DD
− 3
2
1000
0.3
±25
2.4
0.8
±10
10
K, B Versions
16
±4
±8
±0.5
±6
±16
±6
±16
±1
±1
±2
±4
±0.5
±4
±16
±4
±12
±4
±8
±1
±1
±1
20
40
V
SS
+ 6 to
V
DD
− 6
V
SS
+ 6 to
V
DD
− 6
V
SS
+ 4 to
V
DD
− 3
2
1000
0.3
±25
2.4
0.8
±10
10
Unit
Bits
LSB typ
LSB max
LSB max
LSB typ
LSB max
LSB typ
LSB max
ppm FSR/°C typ
ppm FSR/°C typ
LSB typ
LSB max
LSB max
LSB typ
LSB max
LSB typ
LSB max
LSB typ
LSB max
ppm FSR/°Ctyp
ppm FSR/°Ctyp
ppm FSR/°Ctyp
kΩ min
kΩ max
V min to
V max
V min to
V max
V max
kΩ min
pF max
Ω typ
mA typ
V min
V max
μA max
pF max
To 0 V
To 0 V
To 0 V or any power supply
Test Conditions/Comments
V
REF−
= 0 V, V
OUT
= 0 V to +10 V
1 LSB = 153 μV
All grades guaranteed monotonic
V
OUT
load = 10 MΩ
V
REF−
= –5 V, V
OUT
= −10 V to +10 V
1 LSB = 305 μV
All grades guaranteed monotonic
V
OUT
load = 10 MΩ
V
OUT
load = 10 MΩ
Resistance from V
REF+
to V
REF−
Typically 30 kΩ
Rev. G | Page 3 of 24
AD7846
Parameter
1
DIGITAL OUTPUTS
V
OL
(Output Low Voltage)
V
OH
(Output High Voltage)
Floating State Leakage Current
Floating State Output Capacitance
2
POWER REQUIREMENTS
3
V
DD
V
SS
V
CC
I
DD
I
SS
I
CC
Power Supply Sensitivity
4
Power Dissipation
1
2
J, A Versions
0.4
4.0
±10
10
+11.4/+15.75
−11.4/−15.75
+4.75/+5.25
5
5
1
1.5
100
K, B Versions
0.4
4.0
±10
10
+11.4/+15.75
−11.4/−15.75
+4.75/+5.25
5
5
1
1.5
100
Unit
V max
V min
μA max
pF max
V min/V max
V min/V max
V min/V max
mA max
mA max
mA max
LSB/V max
mW typ
Test Conditions/Comments
I
SINK
= 1.6 mA
I
SOURCE
= 400 μA
DB0 to DB15 = 0 to V
CC
V
OUT
unloaded
V
OUT
unloaded
V
OUT
unloaded
Temperature ranges as follows: J, K versions: 0°C to +70°C; A, B versions: −40°C to +85°C.
Guaranteed by design and characterization, not production tested.
3
The AD7846 is functional with power supplies of ±12 V. See the Typical Performance Characteristics section.
4
Sensitivity of gain error, offset error, and bipolar zero error to V
DD
, V
SS
variations.
AC PERFORMANCE CHARACTERISTICS
These characteristics are included for design guidance and are not subject to test. V
REF+
= +5 V; V
DD
= +14.25 V to +15.75 V; V
SS
= −14.25 V
to −15.75 V; V
CC
= +4.75 V to +5.25 V; R
IN
connected to 0 V, unless otherwise noted.
Table 2.
Parameter
Output Settling Time
1
Slew Rate
Digital-to-Analog Glitch
Impulse
AC Feedthrough
Digital Feedthrough
Output Noise Voltage
Density, 1 kHz to 100 kHz
1
Limit at T
MIN
to T
MAX
(All Versions)
6
9
7
70
0.5
10
50
Unit
μs max
μs max
V/μs typ
nV-sec typ
mV p-p typ
nV-sec typ
nV/√Hz typ
Test Conditions/Comments
To 0.006% FSR, V
OUT
loaded, V
REF−
= 0 V, typically 3.5 μs
To 0.003% FSR, V
OUT
loaded, V
REF−
= –5 V, typically 6.5 μs
DAC alternately loaded with 10…0000 and 01…1111,
V
OUT
unloaded
V
REF−
= 0 V, V
REF+
= 1 V rms, 10 kHz sine wave, DAC loaded
with all 0s
DAC alternately loaded with all 1s and all 0s. CS high
Measured at V
OUT
, DAC loaded with 0111011…11,
V
REF+
= V
REF−
= 0 V
LDAC = 0. Settling time does not include deglitching time of 2.5
μs
(typ).
Rev. G | Page 4 of 24
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