1
DAC7631
DAC7631
1999 Burr-Brown Corporation
PDS-1536A
Printed in U.S.A. August, 2000
Serial Input, 16-Bit, Voltage Output
DIGITAL-TO-ANALOG CONVERTER
FEATURES
q
LOW POWER: 2.5mW
q
UNIPOLAR OR BIPOLAR OPERATION
q
SETTLING TIME: 10
s to 0.003%
q
15-BIT LINEARITY AND MONOTONICITY:
40
C to +85
C
q
USER SELECTABLE RESET TO
MID-SCALE OR ZERO-SCALE
q
SMALL SSOP-20 PACKAGE
APPLICATIONS
q
ATE PIN ELECTRONICS
q
PROCESS CONTROL
q
CLOSED-LOOP SERVO-CONTROL
q
MOTOR CONTROL
q
DATA ACQUISITION SYSTEMS
DESCRIPTION
The DAC7631 is a serial input, 16-bit, voltage out-
put Digital-to-Analog Converter (D/A) with guaran-
teed 15-bit monotonic performance over the 40
C to
+85
C temperature range. An asynchronous reset clears
all registers to either mid-scale (8000
H
) or zero-scale
(0000
H
), selectable via the RESETSEL pin. The de-
vice can be powered from a single +5V supply or from
dual +5V and 5V supplies.
International Airport Industrial Park Mailing Address: PO Box 11400, Tucson, AZ 85734 Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 Tel: (520) 746-1111
Twx: 910-952-1111 Internet: http://www.burr-brown.com/ Cable: BBRCORP Telex: 066-6491 FAX: (520) 889-1510 Immediate Product Info: (800) 548-6132
Low power and small size makes the DAC7631 ideal
for process control, data acquisition systems, and
closed-loop servo-control. The device is available in a
SSOP-20 package, and is guaranteed over the
40
C to +85
C temperature range.
DAC7631
DAC A
DAC
Register
Input
Register
Shift
Register
DAC7631
V
REF
L
V
REF
H
V
REF
H
Sense
V
REF
L
Sense
V
OUT
RSTSEL
DGND
LDAC
SDI
AGND
CLK
CS
RST
LOAD
V
OUT
Sense
V
SS
V
CC
SDO
V
DD
For most current data sheet and other product
information, visit www.burr-brown.com
SBAS122
2
DAC7631
DAC7631E
DAC7631EB
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
ACCURACY
Linearity Error
3
4
2
3
LSB
Differential Linearity Error
2
3
1
2
LSB
Monotonicity, T
MIN
to T
MAX
14
15
Bits
Bipolar Zero Error
1
2
T
T
mV
Bipolar Zero Error Drift
5
10
T
T
ppm/
C
Full-Scale Error
1
2
T
T
mV
Full-Scale Error Drift
5
10
T
T
ppm/
C
Power Supply Rejection Ratio (PSRR)
At Full Scale
10
100
T
T
ppm/V
ANALOG OUTPUT
Voltage Output
V
REF
= 2.5V, R
L
= 10k
, V
SS
= 5V
V
REF
L
V
REF
H
T
T
V
Output Current
1.25
+1.25
T
T
mA
Maximum Load Capacitance
No Oscillation
500
T
pF
Short-Circuit Current
10, +30
T
mA
Short-Circuit Duration
GND or V
CC
or V
SS
Indefinite
T
REFERENCE INPUT
Ref High Input Voltage Range
V
REF
L + 1.25
+2.5
T
T
V
Ref Low Input Voltage Range
2.5
V
REF
H 1.25
T
T
V
Ref High Input Current
500
T
A
Ref Low Input Current
500
T
A
DYNAMIC PERFORMANCE
Settling Time
To
0.003%, 5V Output Step
8
10
T
T
s
Digital Feedthrough
2
T
nV-s
Output Noise Voltage
f = 10kHz
60
T
nV/
Hz
DAC Glitch
7FFF
H
to 8000
H
or 8000
H
to 7FFF
H
40
T
nV-s
DIGITAL INPUT
V
IH
0.7 V
DD
T
V
V
IL
0.3 V
DD
T
V
I
IH
10
T
A
I
IL
10
T
A
DIGITAL OUTPUT
V
OH
I
OH
= 0.8mA
3.6
4.5
T
T
V
V
OL
I
OL
= 1.6mA
0.3
0.4
T
T
V
POWER SUPPLY
V
DD
+4.75
+5.0
+5.25
T
T
T
V
V
CC
+4.75
+5.0
+5.25
T
T
T
V
V
SS
5.25
5.0
4.75
T
T
T
V
I
CC
0.4
0.5
T
T
mA
I
DD
50
T
A
I
SS
0.6
0.5
T
T
mA
Power
4
5.5
T
T
mW
TEMPERATURE RANGE
Specified Performance
40
+85
T
T
C
T
Specifications same as DAC7631E.
SPECIFICATIONS (Dual Supply)
At T
A
= T
MIN
to T
MAX
, V
DD
= V
CC
= +5V, V
SS
= 5V, V
REF
H = +2.5V, and V
REF
L = 2.5V, unless otherwise noted.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user's own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
3
DAC7631
DAC7631E
DAC7631EB
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
ACCURACY
Linearity Error
(1)
3
4
2
3
LSB
Differential Linearity Error
2
3
1
2
LSB
Monotonicity, T
MIN
to T
MAX
14
15
Bits
Zero Scale Error
1
2
T
T
mV
Zero Scale Error Drift
5
10
T
T
ppm/
C
Full-Scale Error
1
2
T
T
mV
Full-Scale Error Drift
5
10
T
T
ppm/
C
Power Supply Rejection Ratio (PSRR)
At Full Scale
10
100
T
T
ppm/V
ANALOG OUTPUT
Voltage Output
V
REF
L = 0V, V
SS
= 0V, R
L
= 10k
0
V
REF
H
T
T
V
Output Current
1.25
+1.25
T
T
mA
Maximum Load Capacitance
No Oscillation
500
T
pF
Short-Circuit Current
30
T
mA
Short-Circuit Duration
GND or V
CC
Indefinite
T
REFERENCE INPUT
Ref High Input Voltage Range
V
REF
L + 1.25
+2.5
T
T
V
Ref Low Input Voltage Range
0
V
REF
H 1.25
T
T
V
Ref High Input Current
250
T
A
Ref Low Input Current
250
T
A
DYNAMIC PERFORMANCE
Settling Time
To
0.003%, 2.5V Output Step
8
10
T
T
s
Digital Feedthrough
2
T
nV-s
Output Noise Voltage, f = 10kHz
60
T
nV/
Hz
DAC Glitch
7FFF
H
to 8000
H
or 8000
H
to 7FFF
H
40
T
nV-s
DIGITAL INPUT
V
IH
0.7 V
DD
T
V
V
IL
0.3 V
DD
T
V
I
IH
10
T
A
I
IL
10
T
A
DIGITAL OUTPUT
V
OH
I
OH
= 0.8mA
3.6
4.5
T
T
V
V
OL
I
OL
= 1.6mA
0.3
0.4
T
T
V
POWER SUPPLY
V
DD
+4.75
+5.0
+5.25
T
T
T
V
V
CC
+4.75
+5.0
+5.25
T
T
T
V
V
SS
0
0
0
T
T
T
V
I
CC
0.4
0.5
T
T
mA
I
DD
50
T
A
Power
1.8
2.5
T
T
mW
TEMPERATURE RANGE
Specified Performance
40
+85
T
T
C
NOTE: (1) If V
SS
= 0V specification applies at Code 0040
H
and above due to possible negative zero-scale error.
T
Specifications same as DAC7631E.
SPECIFICATIONS (Single Supply)
At T
A
= T
MIN
to T
MAX
, V
DD
= V
CC
= +5V, V
SS
= 0V, V
REF
H = +2.5V, and V
REF
L = 0V, unless otherwise noted.
4
DAC7631
ABSOLUTE MAXIMUM RATINGS
(1)
V
DD
to V
SS
........................................................................... 0.3V to +11V
V
DD
to GND ........................................................................ 0.3V to +5.5V
V
REFL
to V
SS
............................................................... 0.3V to (V
DD
V
SS
)
V
DD
to V
REFH
.............................................................. 0.3V to (V
DD
V
SS
)
V
REFH
to V
REFL
............................................................ 0.3V to (V
DD
V
SS
)
Digital Input Voltage to GND ...................................... 0.3V to V
DD
+ 0.3V
Maximum Junction Temperature ................................................... +150
C
Operating Temperature Range ......................................... 40
C to +85
C
Storage Temperature Range .......................................... 65
C to +150
C
Lead Temperature (soldering, 10s) ............................................... +300
C
NOTE: (1) Stresses above those listed under "Absolute Maximum Ratings" may
cause permanent damage to the device. Exposure to absolute maximum
conditions for extended periods may affect device reliability.
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling
and installation procedures can cause damage.
ESD damage can range from subtle performance degradation
to complete device failure. Precision integrated circuits may
be more susceptible to damage because very small parametric
changes could cause the device not to meet its published
specifications.
PACKAGE/ORDERING INFORMATION
MAXIMUM
MAXIMUM
LINEARITY
DIFFERENTIAL
PACKAGE
SPECIFICATION
ERROR
LINEARITY
DRAWING
TEMPERATURE
ORDERING
TRANSPORT
PRODUCT
(LSB)
(LSB)
PACKAGE
NUMBER
RANGE
NUMBER
(1)
MEDIA
DAC7631E
4
3
SSOP-20
334
40
C to +85
C
DAC7631E
Rails
"
"
"
"
"
"
DAC7631E/1K
Tape and Reel
DAC7631EB
3
2
SSOP-20
334
40
C to +85
C
DAC7631EB
Rails
"
"
"
"
"
"
DAC7631EB/1K
Tape and Reel
NOTE : (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /1K indicates 1000 devices per reel). Ordering 1000 pieces
of "DAC7631E/1K" will get a single 1000-piece Tape and Reel.
5
DAC7631
PIN
LABEL
DESCRIPTION
1
V
REF
H
DAC Reference High Input
2
V
REF
H Sense
DAC Reference Sense High Input
3
V
REF
L
DAC Reference Low Input
4
V
REF
L Sense
DAC Reference Sense Low Input
5
DGND
Digital Ground
6
V
DD
Logic Power Supply
7
SDO
Serial Data Output
8
SDI
Serial Data Input
9
CLK
Data Clock
10
CS
Chip Select, Active LOW.
11
LDAC
DAC Register Load Control, Rising Edge Triggered.
12
LOAD
DAC Input Register Load Control, Active LOW.
13
RST
Reset, Rising Edge. Depending on the state of
RSTSEL, the DAC Register is set to either midscale
or zero.
14
RSTSEL
Reset Select. Determines the action of RST. If
HIGH, a RST command will set the DAC register to
midscale. If low, a RST command will set the DAC
register to zero.
15
NC
No Connection
16
V
OUT
DAC Voltage Output
17
V
OUT
Sense
DAC Output Amplifier Inverting Input, Used to
Close the Feedback Loop at the Load.
18
V
SS
Negative Power Supply
19
AGND
Analog Ground
20
V
CC
Positive Power Supply
PIN CONFIGURATION
Top View
SSOP
PIN DESCRIPTIONS
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
V
REF
H
V
REF
H Sense
V
REF
L
V
REF
L Sense
DGND
V
DD
SDO
SDI
CLK
CS
V
CC
AGND
V
SS
V
OUT
Sense
V
OUT
NC
RSTSEL
RST
LOAD
LDAC
DAC7631
6
DAC7631
TYPICAL PERFORMANCE CURVES: V
SS
= 0V
At T
A
= +25
C, V
DD
= V
CC
= +5V, V
SS
= 0V, V
REFH
= +2.5V, and V
REFL
= 0V, representative unit, unless otherwise specified.
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(+25
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
2.5
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(+85
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(40
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
30 20 10 0
10 20
30
40 50
60 70
80
90
40
Temperature (
C)
ZERO-SCALE ERROR vs TEMPERATURE
(Code 0040
H
)
Zero-Scale Error (mV)
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
30 20 10 0
10 20
30
40 50
60 70
80
90
40
Temperature (
C)
POSITIVE FULL-SCALE ERROR vs TEMPERATURE
(Code FFFF
H
)
Positive Full-Scale Error (mV)
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
V
REFH
CURRENT vs CODE
Digital Input Code
V
REF
Current (mA)
0000
H
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
2000
H
4000
H
6000
H
8000
H
A000
H
C000
H
E000
H
FFFF
H
7
DAC7631
TYPICAL PERFORMANCE CURVES: V
SS
= 0V
(Cont.)
At T
A
= +25
C, V
DD
= V
CC
= +5V, V
SS
= 0V, V
REFH
= +2.5V, and V
REFL
= 0V, representative unit, unless otherwise specified.
V
REFL
CURRENT vs CODE
Digital Input Code
V
REF
Current (mA)
0000
H
0
0.02
0.04
0.06
0.08
0.10
0.12
0.14
2000
H
4000
H
6000
H
8000
H
A000
H
C000
H
E000
H
FFFF
H
POWER SUPPLY CURRENT vs TEMPERATURE
Data = FFFF
H
No Load
1.0
0.8
0.6
0.4
0.2
0
0.2
0.4
0.6
0.8
1.0
Quiescent Current (mA)
Temperature (
C)
40 30 20 10 0
10
20
30 40
50
60 70 80
90
I
CC
POSITIVE SUPPLY CURRENT
vs DIGITAL INPUT CODE
Digital Input Code
I
CC
I
CC
(mA)
0000
H
0200
H
0400
H
0800
H
1000
H
2000
H
4000
H
6000
H
8000
H
A000
H
C000
H
E000
H
FFFF
H
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
+5V
LDAC
0
Time (2
s/div)
OUTPUT VOLTAGE vs SETTLING TIME
(0V to +2.5V)
Output Voltage
Large-Signal Settling Time: 0.5V/div
Small-Signal Settling Time: 4LSB/div
Time (2
s/div)
OUTPUT VOLTAGE vs SETTLING TIME
(+2.5V to 2mV)
Output Voltage
+5V
LDAC
0
Large-Signal Settling Time: 0.5V/div
Small-Signal Settling Time: 4LSB/div
Time (1
s/div)
OUTPUT VOLTAGE
vs MIDSCALE GLITCH PERFORMANCE
Output Voltage (50mV/div)
+5V
LDAC
0
7FFF
H
to 8000
H
8
DAC7631
TYPICAL PERFORMANCE CURVES: V
SS
= 0V
(Cont.)
At T
A
= +25
C, V
DD
= V
CC
= +5V, V
SS
= 0V, V
REFH
= +2.5V, and V
REFL
= 0V, representative unit, unless otherwise specified.
Time (1
s/div)
OUTPUT VOLTAGE
vs MIDSCALE GLITCH PERFORMANCE
Output Voltage (50mV/div)
+5V
LDAC
0
8000
H
to 7FFF
H
1000
100
10
Frequency (Hz)
10
100
1000
10000
100000
1000000
OUTPUT NOISE VOLTAGE vs FREQUENCY
Noise (nV/
Hz)
5
4
3
2
1
0
R
LOAD
(k
)
0.01
0.1
1
10
100
OUTPUT VOLTAGE vs R
LOAD
V
OUT
(V)
Source
Sink
BROADBAND NOISE
Time (10ms/div)
Noise Voltage (50
V/div)
BW = 10kHz
Code = 8000
H
9
DAC7631
TYPICAL PERFORMANCE CURVES: V
SS
= 5V
At T
A
= +25
C, V
DD
= V
CC
= +5V, V
SS
= 5V, V
REFH
= +2.5V, and V
REFL
= 2.5V, representative unit, unless otherwise specified.
1.0
0.5
0
0.5
1.0
1.5
2.0
2.5
3.0
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(+25
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
V
REFH
CURRENT vs CODE
Digital Input Code
V
REF
Current (mA)
0000
H
0.30
0.25
0.20
0.15
0.10
0.05
0
2000
H
4000
H
6000
H
8000
H
A000
H
C000
H
E000
H
FFFF
H
V
REFL
CURRENT vs CODE
Digital Input Code
V
REF
Current (mA)
0000
H
0
0.05
0.10
0.15
0.20
0.25
0.30
2000
H
4000
H
6000
H
8000
H
A000
H
C000
H
E000
H
FFFF
H
30 20 10 0
10 20
30
40 50
60 70
80
90
40
Temperature (
C)
BIPOLAR ZERO-SCALE ERROR vs TEMPERATURE
(Code 8000
H
)
Bipolar Zero-Scale Error (mV)
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(40
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
0.5
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(+85
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
10
DAC7631
TYPICAL PERFORMANCE CURVES: V
SS
= 5V
(Cont.)
At T
A
= +25
C, V
DD
= V
CC
= +5V, V
SS
= 5V, V
REFH
= +2.5V, and V
REFL
= 2.5V, representative unit, unless otherwise specified.
30 20 10 0
10 20
30
40 50
60 70
80
90
40
Temperature (
C)
NEGATIVE FULL-SCALE ERROR vs TEMPERATURE
(Code 0000
H
)
Negative Full-Scale Error (mV)
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
POWER SUPPLY CURRENT vs TEMPERATURE
Data = FFFF
H
No Load
1.0
0.8
0.6
0.4
0.2
0
0.2
0.4
0.6
0.8
1.0
Quiescent Current (mA)
Temperature (
C)
40 30 20 10 0
10
20
30 40
50
60 70 80
90
I
CC
I
SS
5
4
3
2
1
0
1
2
3
4
5
R
LOAD
(k
)
0.001
0.01
1
0.1
100
10
1000
V
OUT
vs R
LOAD
V
OUT
(V)
Source
Sink
POSITIVE SUPPLY CURRENT
vs DIGITAL INPUT CODE
Digital Input Code
I
CC
I
CC
(mA)
0000
H
0200
H
0400
H
0800
H
1000
H
2000
H
4000
H
6000
H
8000
H
A000
H
C000
H
E000
H
FFFF
H
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
Time (2
s/div)
OUTPUT VOLTAGE vs SETTLING TIME
(2.5V to +2.5V)
Output Voltage
+5V
LDAC
0
Large-Signal Settling Time: 1V/div
Small-Signal Settling Time: 2LSB/div
30 20 10 0
10 20
30
40 50
60 70
80
90
40
Temperature (
C)
POSITIVE FULL-SCALE ERROR vs TEMPERATURE
(Code FFFF
H
)
Positive Full-Scale Error (mV)
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
11
DAC7631
TYPICAL PERFORMANCE CURVES: V
SS
= 5V
(Cont.)
At T
A
= +25
C, V
DD
= V
CC
= +5V, V
SS
= 5V, V
REFH
= +2.5V, and V
REFL
= 2.5V, representative unit, unless otherwise specified.
Time (2
s/div)
OUTPUT VOLTAGE vs SETTLING TIME
(+2.5V to 2.5V)
Output Voltage
Large-Signal Settling Time: 1V/div
Small-Signal Settling Time:
2LSB/div
+5V
LDAC
0
THEORY OF OPERATION
The DAC7631 is a 16-bit voltage-output Digital-to-Analog
Converter (DAC). The architecture is an R-2R ladder con-
figuration with the three MSB's segmented, followed by an
operational amplifier that serves as a buffer, as shown in
Figure 1. The minimum voltage output (zero-scale) and
maximum voltage output (full-scale) are set by external
voltage references at V
REF
L and V
REF
H, respectively.
The digital input is a 16-bit serial word representing the
16-bit DAC input code, sent MSB first. The DAC7631 can
be powered from either a single +5V supply or a dual
5V
supply. The device offers a reset function which immedi-
ately sets the output voltage and DAC register to mid-scale
code (8000H) or to zero-scale code (0000H). See Figures 2
and 3 for the basic operation of the DAC7631.
R
2R
2R
2R
2R
2R
2R
2R
2R
2R
V
REF
H
V
OUT
V
OUT
Sense
V
REF
H Sense
V
REF
L
V
REF
L Sense
R
F
FIGURE 1. DAC7631 Architecture.
12
DAC7631
ANALOG OUTPUTS
When V
SS
= 5V (dual supply operation), the output ampli-
fier can swing to within 2.25V of the supply rails, guaran-
teed over the 40
C to +85
C temperature range. When
V
SS
= 0V (single-supply operation), and with R
LOAD
also
connected to ground, the output can swing to ground. Care
must also be taken when measuring the zero-scale error
when V
SS
= 0V. Since the output voltage cannot swing
below ground, the output voltage may not change for the
first few digital input codes (0000
H
, 0001
H
, 0002
H
, etc.) if
the output amplifier has a negative offset. At the negative
limit of 2mV, the first specified output starts at code 0040
H
.
Due to the high accuracy of these D/A converters, system
design problems such as grounding and contact resistance
become very important. A 16-bit converter with a 2.5V full-
scale range has a 1LSB value of 38
V. With a load current
of 1mA, series wiring and connector resistance of only
40m
(R
W2
) will cause a voltage drop of 40
V, as shown in
Figure 4. To understand what this means in terms of a
system layout, the resistivity of a typical 1 ounce copper-
clad printed circuit board is 1/2 m
per square. For a 1mA
FIGURE 2. Basic Single-Supply Operation.
FIGURE 3. Basic Dual-Supply Operation.
load, a 10 milli-inch wide printed circuit conductor 600
milli-inches long will result in a voltage drop of 30
V.
The DAC7631 offers a force and sense output configuration
for the high open-loop gain output amplifier. This feature
allows the loop around the output amplifier to be closed at
the load (as shown in Figure 4), thus ensuring an accurate
output voltage.
REFERENCE INPUTS
The reference inputs, V
REF
L and V
REF
H, can be any voltage
between V
SS
+ 2.5V and V
CC
2.5V, provided that V
REF
H
is at least 1.25V greater than V
REF
L. The minimum output of
each DAC is equal to V
REF
L
plus a small offset voltage
(essentially, the offset of the output op amp). The maximum
output is equal to V
REF
H plus a similar offset voltage. Note
that V
SS
(the negative power supply) must either be
connected to ground or must be in the range of 4.75V to
5.25V. The voltage on V
SS
sets several bias points within
the converter. If V
SS
is not in one of these two configura-
tions, the bias values may be in error and proper operation
of the device is not guaranteed.
Reset DAC Registers
Chip Select
DGND
V
DD
SDI
CLK
CS
V
CC
AGND
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
DAC7631
V
REF
H Sense
V
REF
H
V
REF
L Sense
V
REF
L
SDO
V
SS
V
OUT
Sense
V
OUT
NC
RSTSEL
RST
LOAD
Serial Data In
Clock
Load DAC Registers
Load
LDAC
Serial Data Out
+
0.1
F
1
F
+5V
+2.5000V
0V to +2.5V
Reset DAC Registers
Chip Select
DGND
V
DD
SDI
CLK
CS
V
CC
AGND
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
DAC7631
V
REF
H Sense
V
REF
H
V
REF
L Sense
V
REF
L
SDO
V
SS
V
OUT
Sense
V
OUT
NC
RSTSEL
RST
Serial Data In
Clock
Load DAC Registers
Load
LDAC
LOAD
Serial Data Out
+
+
0.1
F
0.1
F
1
F
+
+5V
1
F
0.1
F
1
F
+5V
5V
+2.5000V
2.5000V
2.5V to +2.5V
13
DAC7631
The current into the V
REF
H input and out of V
REF
L depends
on the DAC output voltage, and can vary from a few
microamps to approximately 0.3mA in dual supply or 0.15mA
in single-supply operation. The reference input appears as a
varying load to the reference. If the reference can sink or
source the required current, a reference buffer is not re-
quired. The DAC7631 features a reference drive and sense
connection such that the internal errors caused by the chang-
ing reference current and the circuit impedances can be
minimized. Figures 5 through 13 show different reference
configurations, and the effect on the linearity and differen-
tial linearity.
Reset DAC Registers
Chip Select
DGND
V
DD
SDI
CLK
CS
V
CC
AGND
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
DAC7631
V
REF
H Sense
V
REF
H
V
REF
L Sense
V
REF
L
SDO
V
SS
V
OUT
Sense
V
OUT
NC
RSTSEL
RST
Serial Data In
Clock
Load DAC Registers
Load
LDAC
LOAD
Serial Data Out
0.1
F
1
F
+
+5V
V
OUT
R
W1
R
W2
+2.5V
+V
DIGITAL INTERFACE
Table I shows the basic control logic for the DAC7631. The
interface consists of a serial clock input (CLK), serial data
input (SDI), DAC input register load control signal (LOAD),
and DAC load control signal (LDAC). In addition, a chip
select input (CS) is provided to simplify device selection in
systems with multiple devices. An asynchronous reset input
(RST), triggered by a rising edge, is provided to force start-
up conditions, periodic resets, or emergency resets to a
known state. The action of RST can be selected using the
reset select (RSTSEL) pin.
INPUT
DAC
CS
RST
RSTSEL
LDAC
LOAD
REGISTER
REGISTER
MODE
L
H
X
X
L
Write
Hold
Write Input
H
H
X
H
Hold
Write
Update
H
H
X
H
H
Hold
Hold
Hold
X
L
X
X
Reset to Zero
Reset to Zero
Reset to Zero
X
H
X
X
Reset to Midscale
Reset to Midscale
Reset to Midscale
TABLE I. DAC7631 Logic Truth Table.
B15
B14
B13
B12
B11
B10
B9
B8
B7
B6
B5
B4
B3
B2
B1
B0
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
SERIAL DATA INPUT
FIGURE 4. Analog Output Closed-loop Configuration. R
W1
and R
W2
represent wiring resistance.
FIGURE 5. Dual-supply Buffered References.
+V
+2.5V
2.5V
V
+V
OPA2234
V
2200pF
2200pF
100
100
1000pF
1000pF
1
2
3
4
V
REF
H
V
REF
H Sense
V
REF
L
V
REF
L Sense
DAC7631
14
DAC7631
FIGURE 6. Single-supply Buffered Reference, V
REF
L = 50mV.
FIGURE 9. Single-supply Buffered Reference, V
REF
L = +1.25V, V
REF
H = 1.25V.
FIGURE 7. Integral Linearity and Differential Linearity
Error Curves for Figure 6.
FIGURE 8. Integral Linearity and Differential Linearity
Error Curves for Figure 9.
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(DAC A, +25
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(DAC A, +25
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
2k
+0.050V
+V
98k
+2.5V
+V
OPA2350
2200pF
2200pF
100
100
1000pF
1000pF
1
2
3
4
V
REF
H
V
REF
H Sense
V
REF
L
V
REF
L Sense
DAC7631
NOTE: V
REF
L has been chosen to be 50mV to allow for current sinking voltage
drops across the 100
resistor and the output stage of the buffer op amp.
+V
+V
+1.25V
+2.5V
+V
OPA2350
2200pF
2200pF
100
100
1000pF
1000pF
1
2
3
4
V
REF
H
V
REF
H Sense
V
REF
L
V
REF
L Sense
DAC7631
15
DAC7631
FIGURE 10. Single-supply Buffered V
REF
H.
FIGURE 11. Linearity and Differential Error Curves for
Figure 10.
FIGURE 13. Linearity and Differential Error Curves for
Figure 12.
FIGURE 12. Low cost Single-supply Configuration.
Data is shifted into the device through the SDI and CLK pins
and arrives in a shift register. Once all 16 bits have been
transferred, the LOAD pin, which is level-sensitive, should
be brought low to latch the data into a buffer register called
the DAC input register. To latch the new data into the DAC
itself, the LDAC pin, which is edge-sensitive, must be
brought high. When this is done, the DAC will assume the
new value and the output voltage will change (provided that
the new value is different from the old one). Note that
settling time is measured from the time that the LDAC pin
is brought high, since the device's output does not begin to
change until then.
The DAC7631's double-buffering scheme allows the device
to be updated through the serial interface without disturbing
the voltage on the output pin. It also allows the user to use
separate logic for driving the serial input and triggering
2.5
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(DAC A, +25
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
Reset DAC Registers
Chip Select
Load
DGND
V
CC
SDI
CLK
CS
V
CC
AGND
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
DAC7631
V
REF
H Sense
V
REF
H
V
REF
L Sense
V
REF
L
SDO
V
SS
V
OUT
Sense
V
OUT
NC
RSTSEL
RST
LOAD
Serial Data In
Clock
Load DAC Registers
LDAC
Serial Data Out
+
0.1
F
1
F
+5V
+2.5V
+V
V
OUT
2.5
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
2.5
2.0
1.5
1.0
0.5
0
0.5
1.0
1.5
2.0
LE (LSB)
DLE (LSB)
LINEARITY ERROR AND
DIFFERENTIAL LINEARITY ERROR vs CODE
(DAC A, +25
C)
0000
H
2000
H
4000
H
6000
H
8000
H
Digital Input Code
A000
H
C000
H
E000
H
FFFF
H
+2.5V
+V
+V
OPA2350
2200pF
100
1000pF
1
2
3
4
V
REF
H
V
REF
H Sense
V
REF
L
V
REF
L Sense
DAC7631
16
DAC7631
DAC updates; i.e., the LDAC pin can be driven with a
separate signal, such as a timing clock, which need not be
directly related to the serial data timing. This makes it easy
to synchronize DAC7631 updates with external events or
with other DACs.
Note that CS and CLK are combined with an OR gate, which
controls the serial-to-parallel shift register. These two inputs
are completely interchangeable. In addition, care must be
taken with the state of CLK when CS rises at the end of a
serial transfer. If CLK is LOW when CS rises, the OR gate
will provide a rising edge to the shift register, shifting the
internal data one additional bit. The result will be incorrect
data and possible selection of the wrong input register(s). If
both CS and CLK are used, CS should rise only when CLK
is HIGH. If not, then either CS or CLK can be used to
operate the shift register. See Table II for more information.
DIGITAL TIMING
Figure 15 and Table III provide detailed timing for the
digital interface of the DAC7631.
DIGITAL INPUT CODING
The DAC7631 input data is in Straight Binary format. The
output voltage is given by Equation 1:
V
V
L
V
H
V
L
N
OUT
REF
REF
REF
=
+
(
)
,
65 536
(1)
where N is the digital input code. This equation does not
include the effects of offset (zero-scale) or gain (full-scale)
errors.
DIGITALLY-PROGRAMMABLE
CURRENT SOURCE
The DAC7631 offers a unique set of features that allows a
wide range of flexibility in designing applications circuits
such as programmable current sources. The DAC7631 offers
both a differential reference input, as well as an open-loop
configuration around the output amplifier. The open-loop
configuration around the output amplifier allows a transistor
to be placed within the loop to implement a digitally-
programmable, unidirectional current source. The availabil-
ity of a differential reference allows programmability for
both the full-scale and zero-scale currents. The output cur-
rent is calculated as:
I
V
H
V
L
R
V
L R
OUT
REF
REF
SENSE
REF
SENSE
=
+
(
)
,
/
N
65 536
(2)
CS
(1)
CLK
(1)
LOAD
RST
SERIAL SHIFT REGISTER
H
(2)
X
(3)
H
H
No Change
L
(4)
L
H
H
No Change
L
(5)
H
H
Advanced One Bit
L
H
H
Advanced One Bit
H
(6)
X
L
(7)
H
No Change
H
(6)
X
H
(8)
No Change
NOTES: (1) CS and CLK are interchangeable. (2) H = Logic HIGH.
(3) X = Don't Care. (4) L = Logic LOW (5) = Positive Logic Transition.
(6) A HIGH value is suggested in order to avoid a "false clock" from
advancing the shift register and changing the shift register. (7) If data is
clocked into the serial register while LOAD is LOW, the DAC register will
change. This will corrupt the data in each DAC register that has been
erroneously selected. (8) Rising edge of RST causes no change in the
contents of the serial shift register.
TABLE II. Serial Shift Register Truth Table.
DAC7631
CLK
SDI
CS
SCK
DIN
CS
SDO
DAC7631
CLK
SDI
CS
SDO
DAC7631
CLK
SDI
CS
SDO
To
Other
Serial
Devices
FIGURE 14. Daisy-chaining DAC7631.
SERIAL-DATA OUTPUT
The Serial-Data Output (SDO) is the internal shift register's
output. For DAC7631, the SDO is a driven output and does
not require an external pull-up. Any number of DAC7631's
can be daisy chained by connecting the SDO pin of one
device to the SDI pin of the following device in the chain,
as shown in Figure 14.
17
DAC7631
SYMBOL
DESCRIPTION
MIN
MAX
UNITS
t
DS
Data Valid to CLK Rising
10
ns
t
DH
Data Held Valid after CLK Rises
20
ns
t
CH
CLK HIGH
25
ns
t
CL
CLK LOW
25
ns
t
CSS
CS LOW to CLK Rising
15
ns
t
CSH
CLK HIGH to CS Rising
0
ns
t
LD1
LOAD HIGH to CLK Rising
10
ns
t
LD2
CLK Rising to LOAD LOW
30
ns
t
LDRW
LOAD LOW Time
30
ns
t
LDDL
LDAC LOW Time
100
ns
t
LDDH
LDAC HIGH Time
150
ns
t
SDO
SDO Propagation Delay
10
45
ns
t
RSSS
RESETSEL Valid to RESET HIGH
0
ns
t
RSSH
RESET HIGH to RESETSEL Not Valid
100
ns
t
RSTL
RESET LOW Time
10
ns
t
RSTH
RESET HIGH Time
10
ns
t
LDDD
LOAD LOW to LDAC Rising Time
40
ns
t
S
Settling Time
10
s
TABLE III. Timing Specifications (T
A
= 40
C to +85
C).
FIGURE 15. Digital Input and Output Timing.
D15
(LSB)
SDI
CLK
CS
LOAD
D14
D3
D2
D1
D0
SDI
CLK
LDAC
RESET
V
OUT
tcss
t
LD1
t
CL
t
SDO
t
CH
t
DS
t
DH
t
LD2
t
LDRW
t
S
t
RSTH
t
RSTL
t
RSSS
t
RSSH
SDO
t
CSH
t
S
0.003%
ERROR BAND
1LSB
ERROR BAND
RESETSEL
D11
D10
D9
D12
D13
(MSB)
t
LDDD
LDAC
t
LDDH
t
LDDL
18
DAC7631
Figure 16 shows a DAC7631 in a 4mA to 20mA current
output configuration. The output current can be determined
by Equation 3:
I
V
V
N
V
OUT
=
+
2 5
0 5
125
65 536
0 5
125
.
.
,
.
(3)
At full-scale, the output current is 16mA, plus the 4mA, for
the zero current. At zero scale the output current is the offset
current of 4mA (0.5V/125
).
FIGURE 16. 4-to-20mA Digitally Controlled Current Source (1/2 DAC7631).
Reset DAC Registers
Chip Select
Load
DGND
V
DD
SDI
CLK
CS
V
CC
I
OUT
125
V
PROGRAMMED
AGND
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
DAC7631
OPA2350
+V
+V
+2.5V
V
REF
H Sense
V
REF
H
V
REF
L Sense
V
REF
L
SDO
V
SS
V
OUT
Sense
V
OUT
NC
RSTSEL
RST
LOAD
Serial Data In
Clock
Load DAC Registers
LDAC
Serial Data Out
+
0.1
F
1
F
+5V
20k
80k
100
2200pF
2200pF
1000pF
1000pF
100
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package
Type
Package
Drawing
Pins Package
Qty
Eco Plan
(2)
Lead/Ball Finish
MSL Peak Temp
(3)
DAC7631E
ACTIVE
SSOP
DB
20
68
None
CU SNPB
Level-3-220C-168 HR
DAC7631E/1K
ACTIVE
SSOP
DB
20
1000
None
CU SNPB
Level-3-220C-168 HR
DAC7631EB
ACTIVE
SSOP
DB
20
68
None
CU SNPB
Level-3-220C-168 HR
DAC7631EB/1K
ACTIVE
SSOP
DB
20
1000
None
CU SNPB
Level-3-220C-168 HR
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - May not be currently available - please check
http://www.ti.com/productcontent
for the latest availability information and additional
product content details.
None: Not yet available Lead (Pb-Free).
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
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9-Dec-2004
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