Burr-Brown DAC7541 Low cost 12-bit cmos four-quadrant multiplying digital-to-analog converter Datasheet

DAC7541A
®
Low Cost 12-Bit CMOS
Four-Quadrant Multiplying
DIGITAL-TO-ANALOG CONVERTER
FEATURES
DESCRIPTION
● FULL FOUR-QUADRANT
MULTIPLICATION
● 12-BIT END-POINT LINEARITY
● DIFFERENTIAL LINEARITY ±1/2LSB MAX
OVER TEMPERATURE
● MONOTONICITY GUARANTEED OVER
TEMPERATURE
● TTL-/CMOS-COMPATIBLE
The Burr-Brown DAC7541A is a low cost 12-bit,
four-quadrant multiplying digital-to-analog converter.
Laser-trimmed thin-film resistors on a monolithic
CMOS circuit provide true 12-bit integral and differential linearity over the full specified temperature
range.
DAC7541A is a direct, improved pin-for-pin replacement for 7521, 7541, and 7541A industry standard
parts. In addition to a standard 18-pin plastic package,
the DAC7541A is also available in a surface-mount
plastic 18-pin SOIC.
● SINGLE +5V TO +15V SUPPLY
● LATCH-UP RESISTANT
● 7521/7541/7541A REPLACEMENT
● PACKAGES: Plastic DIP, Plastic SOIC
● LOW COST
10kΩ
VREF
20kΩ
10kΩ
20kΩ
10kΩ
10kΩ
20kΩ
20kΩ
20kΩ
20kΩ
SPDT NMOS
Switches
IOUT 2
IOUT 1
10kΩ
Bit 1
(MSB)
Bit 2
Bit 3
Bit 11
Digital Inputs (DTL-/TTL-/CMOS-compatible)
Logic: A switch is closed to IOUT 1 for its digital input in a “HIGH” state.
International Airport Industrial Park • Mailing Address: PO Box 11400
Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP •
©
1987 Burr-Brown Corporation
Bit 12
(LSB)
RFB
Switches shown for digital inputs “HIGH”.
• Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706
Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
PDS-639C
Printed in U.S.A. September, 1993
SPECIFICATIONS
ELECTRICAL
At +25°C, +VDD = +12V or +15V, VREF = +10V, VPIN 1 = V PIN 2 = 0V, unless otherwise specified.
DAC7541A
PARAMETER
ACCURACY
Resolution
Relative Accuracy
Differential Non-linearity
Gain Error
Gain Temperature Coefficient
(∆Gain/∆Temperature)
Output Leakage Current: Out1 (Pin 1)
Out2 (Pin 2)
REFERENCE INPUT
Voltage (Pin 17 to GND)
Input Resistance (Pin 17 to GND)
GRADE
TA = +25°C
TA = TMAX, TMIN(1)
UNITS
All
J
K
J
K
J
K
12
±1
±1/2
±1
±1/2
±6
±1
12
±1
±1/2
±1
±1/2
±8
±3
Bits
LSB max
LSB max
LSB max
LSB max
LSB max
LSB max
ALL
J, K
J, K
±5
±5
5
±10
±10
ppm/°C max
nA max
nA max
All
All
–10/+10
7-18
–10/+10
7-18
V min/max
kΩ min/max
TEST CONDITIONS/COMMENTS
±1LSB = ±0.024% of FSR.
±1/2LSB = ±0.012% of FSR.
All grades guaranteed monotonic to 12 bits,
TMIN to TMAX.
Measured using internal RFB and includes effect
of leakage current and gain T.C.
Gain error can be trimmed to zero.
Typical value is 2ppm/°C.
All digital inputs = 0V.
All digital inputs = VDD.
Typical input resistance = 11kΩ.
Typical input resistance temperature coefficient is
–50ppm/°C.
DIGITAL INPUTS
VIN (Input HIGH Voltage)
VIL (Input LOW Voltage)
IIN (Input Current)
All
All
All
2.4
0.8
±1
2.4
0.8
±1
V min
V max
µA max
Capacitance)(2)
CIN (Input
All
8
8
pF max
POWER SUPPLY REJECTION
∆Gain/∆VDD
All
±0.01
±0.02
% per % max
POWER SUPPLY
VDD Range
All
+5 to +16
+5 to +16
All
All
2
100
2
500
V min to
V max
mA max
µA max
IDD
Logic inputs are MOS gates.
IIN typ (25°C) = 1nA
VIN = 0V
VDD = +11.4V to +16V
Accuracy is not guaranteed over this range.
All digital inputs VIL or VIN.
All digital inputs 0V or VDD.
NOTES: (1) Temperature ranges are: = 0°C to + 70°C for JP, KP, JU and KU versions. (2) Guaranteed by design but not production tested.
AC PERFORMANCE CHARACTERISTICS
These characteristics are included for design guidance only and are not production tested.
VDD = +15V, VREF = +10V except where stated, VPIN 1 = VPIN 2 = 0V, output amp is OPA606 except where stated.
DAC7541A
GRADE
TA = +25°C
TA = TMAX, TMIN(1)
UNITS
TEST CONDITIONS/COMMENTS
PROPAGATION DELAY
(from Digital Input change to 90% of
final Analog Output)
All
100
—
ns typ
Out1 Load = 100Ω, CEXT = 13pF.
Digital Inputs = 0V to VDD or VDD to 0V.
DIGITAL-TO-ANALOG GLITCH
IMPULSE
All
1000
—
nV-s typ
MULTIPLYING FEEDTHROUGH
ERROR
(VREF to Out1)
All
1.0
—
mVp-p max
All
0.6
—
µs typ
All
1.0
—
µs max
To 0.01% of Full Scale Range.
Out1 Load = 100Ω, CEXT = 13pF.
Digital Inputs: 0V to VDD or VDD to 0V.
All
All
All
All
100
60
70
100
100
60
70
100
pF max
pF max
pF max
pF max
Digital Inputs = VIH
Digital Inputs = VIH
Digital Inputs = VIL
Digital Inputs = VIL
PARAMETER
VREF = 0V, all digital inputs 0V to VDD or VDD to
0V. Measured using OPA606 as output amplifier.
VREF = ±10V, 10kHz sine wave.
OUTPUT CURRENT SETTLING TIME
OUTPUT CAPACITANCE
COUT 1 (Pin 1)
COUT 2 (Pin 2)
COUT 1 (Pin 1)
COUT 2 (Pin 2)
NOTE: (1) Temperature ranges are: = 0°C to + 70°C for JP, KP, JU and KU versions.
®
DAC7541A
2
ABSOLUTE MAXIMUM RATINGS(1)
PIN CONNECTIONS
VDD (Pin 16) to Ground ...................................................................... +17V
VREF (Pin 17) to Ground ..................................................................... +25V
VRPB (Pin 18) to Ground ..................................................................... ±25V
Digital Input Voltage (pins 4-15) to Ground ............................... –0.4V, VDD
VPIN 1, VPIN 2 to Ground ............................................................. –0.4V, VDD
Power Dissipation (any Package):
To +75°C ..................................................................................... 450mW
Derates above +75°C .............................................................. –6mW/°C
Lead Temperature (soldering, 10s) ................................................ +300°C
Storage Temperature: Plastic Package ......................................... +125°C
Top View
DIP/SOIC
IOUT 1
1
18 RFB
IOUT 2
2
17 VREF
GND
3
16 +VDD
Bit 1 (MSB)
4
15 Bit 12 (LSB)
DAC7541A
NOTE: (1) Stresses above those listed above may cause permanent damage to
the device. This is a stress rating only and functional operation of the device at
these or any other condition above those indicated in the operational sections of
this specification is not implied. Exposure to absolute maximum rating conditions
for extended periods may affect device reliability.
ELECTROSTATIC
DISCHARGE SENSITIVITY
Bit 2
5
14 Bit 11
Bit 3
6
13 Bit 10
Bit 4
7
12 Bit 9
Bit 5
8
11 Bit 8
Bit 6
9
10 Bit 7
PACKAGE INFORMATION
The DAC7541A is an ESD (electrostatic discharge) sensitive device. The digital control inputs have a special FET
structure, which turns on when the input exceeds the supply
by 18V, to minimize ESD damage. However, permanent
damage may occur on unconnected devices subject to high
energy electrostatic fields. When not in use, devices must be
stored in conductive foam or shunts. The protective foam
should be discharged to the destination socket before
devices are removed.
MODEL
PACKAGE
PACKAGE DRAWING
NUMBER(1)
DAC7541JP
DAC7541KP
Plastic DIP
Plastic DIP
218
218
DAC7541JU
DAC7541KU
Plastic SOIC
Plastic SOIC
219
219
Plastic DIP
Plastic DIP
218
218
DAC7541JP-BI
DAC7541KP-BI
NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix D of Burr-Brown IC Data Book.
BURN-IN SCREENING
Burn-in screening is an option available for the models in the
Ordering Information table. Burn-in duration is 160 hours at
the indicated temperature (or equivalent combination of time
and temperature).
All units are tested after burn-in to ensure that grade specifications are met. To order burn-in, add “-BI” to the base
model number.
ORDERING INFORMATION
MODEL
DAC7541AJP
DAC7541AKP
DAC7541AJU
DAC7541AKU
PACKAGE
TEMPERATURE
RANGE
RELATIVE
ACCURACY (LSB)
Plastic DIP
Plastic DIP
Plastic SOIC
Plastic SOIC
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
±1
±1/2
±1
±1/2
GAIN ERROR (LSB)
±6
±1
±6
±1
BURN-IN SCREENING OPTION
See text for details.
MODEL
PACKAGE
TEMPERATURE
RANGE
RELATIVE
ACCURACY (LSB)
BURN-IN TEMP.
(160 Hours)(1)
DAC7541AJP-BI
DAC7541AKP-BI
Plastic DIP
Plastic DIP
0°C to +70°C
0°C to +70°C
±1
±1/2
+85°C
+85°C
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
DAC7541A
PAD
FUNCTION
PAD
FUNCTION
1
2
3
4
5
6
7
8
9
IOUT1
IOUT2
GND
Bit 1 (MSB)
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
10
11
12
13
14
15
16
17
18
Bit 7
Bit 8
Bit 9
Bit 10
Bit 11
Bit 12 (LSB)
+VDD
VREF
RFEEDBACK
Substrate Bias: Isolated.
NC: No Connection.
MECHANICAL INFORMATION
Die Size
Die Thickness
Min. Pad Size
MILS (0.001")
MILLIMETERS
104 x 105 ±5
20 ±3
4x4
2.64 x 2.67 ±0.13
0.51 ±0.08
0.10 x 0.10
Metalization
Aluminum
DIE TOPOLOGY DAC7541A
TYPICAL PERFORMANCE CURVES
TA = +25°C, V DD = +15V, unless otherwise noted.
GAIN ERROR vs SUPPLY VOLTAGE
FEEDTHROUGH ERROR vs FREQUENCY
3
10
Feedthrough (% FSR)
Gain Error (LSB)
5/2
2
3/2
1
1
0.10
0.010
1/2
0
0.001
5
0
10
15
100
1k
10k
Supply Voltage (V)
5/4
5/4
Supply Current (µA)
Linearity Error (LSB)
3/2
1
3/4
1/2
1
3/4
VIH = +2.4V
1/2
1/4
1/4
0
0
5
10
15
VIH = VDD
0
Supply Voltage (V)
5
10
Supply Voltage (V)
®
DAC7541A
1M
SUPPLY CURRENT vs SUPPLY VOLTAGE
LINEARITY vs SUPPLY VOLTAGE
3/2
0
100k
Frequency (Hz)
4
15
DISCUSSION
OF SPECIFICATIONS
CIRCUIT DESCRIPTION
The DAC7541A is a 12-bit multiplying D/A converter
consisting of a highly stable thin-film R-2R ladder network
and 12 pairs of current steering switches on a monolithic
chip. Most applications require the addition of a voltage or
current reference and an output operational amplifier.
A simplified circuit of the DAC7541A is shown in Figure 1.
The R-2R inverted ladder binarily divides the input currents
that are switched between IOUT 1 and IOUT 2 bus lines. This
switching allows a constant current to be maintained in each
ladder leg independent of the input code.
RELATIVE ACCURACY
This term (also known as linearity) describes the transfer
function of analog output to digital input code. The linearity
error describes the deviation from a straight line between
zero and full scale.
DIFFERENTIAL NONLINEARITY
Differential nonlinearity is the deviation from an ideal 1LSB
change in the output, from one adjacent output state to the
next. A differential nonlinearity specification of ±1.0LSB
guarantees monotonicity.
The input resistance at VREF (Figure 1) is always equal to
RLDR (RLDR is the R/2R ladder characteristic resistance and
is equal to value “R”). Since RIN at the VREF pin is constant,
the reference terminal can be driven by a reference voltage
or a reference current, AC or DC, of positive or negative
polarity.
GAIN ERROR
Gain error is the difference in measure of full-scale output
versus the ideal DAC output. The ideal output for the
DAC7541A is –(4095/4096) X (VREF). Gain error may be
adjusted to zero using external trims.
10kΩ
VREF
OUTPUT LEAKAGE CURRENT
The measure of current which appears at Out1 with the DAC
loaded with all zeros, or at Out2 with the DAC loaded with
all ones.
20kΩ
S1
10kΩ
20kΩ
S2
10kΩ
20kΩ
20kΩ
S3
20kΩ
S12
IOUT 2
MULTIPLYING FEEDTHROUGH ERROR
This is the AC error output due to capacitive feedthrough
from VREF to Out1 with the DAC loaded with all zeros. This
test is performed at 10kHz.
IOUT 1
RFB
Bit 1
(MSB)
Bit 2
Bit 3
Bit 12
(LSB)
Digital Inputs (DTL-/TTL-/CMOS-compatible)
Switches shown for digital inputs “HIGH”.
OUTPUT CURRENT SETTLING TIME
This is the time required for the output to settle to a tolerance
of ±0.5LSB of final value from a change in code of all zeros
to all ones, or all ones to all zeros.
FIGURE 1. Simplified DAC Circuit.
EQUIVALENT CIRCUIT ANALYSIS
Figures 2 and 3 show the equivalent circuits for all digital
inputs low and high, respectively. The reference current is
switched to IOUT 2 when all inputs are low and IOUT 1 when
inputs are high. The IL current source is the combination of
surface and junction leakages to the substrate; the
1/4096 current source represents the constant one-bit current
drain through the ladder terminal.
PROPAGATION DELAY
This is the measure of the delay of the internal circuitry and
is measured as the time from a digital code change to the
point at which the output reaches 90% of final value.
DIGITAL-TO-ANALOG GLITCH IMPULSE
This is the measure of the area of the glitch energy measured
in nV-seconds. Key contributions to glitch energy are digital
word-bit timing differences, internal circuitry timing differences, and charge injected from digital logic.
DYNAMIC PERFORMANCE
Output Impedance
The output resistance, as in the case of the output capacitance, is also modulated by the digital input code. The
resistance looking back into the IOUT 1 terminal may be
anywhere between 10kΩ (the feedback resistor alone when
all digital inputs are low) and 7.5kΩ (the feedback resistor
in parallel with approximately 30kΩ of the R-2R ladder
network resistance when any single bit logic is high). The
static accuracy and dynamic performance will be affected by
this modulation. The gain and phase stability of the output
MONOTONICITY
Monotonicity assures that the analog output will increase or
stay the same for increasing digital input codes. The
DAC7541A is guaranteed monotonic to 12 bits.
POWER SUPPLY REJECTION
Power supply rejection is the measure of the sensitivity of
the output (full scale) to a change in the power supply
voltage.
®
5
DAC7541A
RFB
RFB
R = 10kΩ
IREF
IOUT 1
IL
IREF
R = 10kΩ
R ≈ 10kΩ
IOUT 1
VREF
1/4096
60pF
IL
90pF
R ≈ 10kΩ
IOUT 2
IOUT 2
VREF
1/4096
IL
IL
90pF
FIGURE 2. DAC7541A Equivalent Circuit (All inputs
LOW).
FIGURE 3. DAC7541A Equivalent Circuit (All inputs
HIGH).
amplifier, board layout, and power supply decoupling will
all affect the dynamic performance of the DAC7541A. The
use of a compensation capacitor may be required when highspeed operational amplifiers are used. It may be connected
across the amplifier’s feedback resistor to provide the necessary phase compensation to critically dampen the output.
See Figures 4 and 6.
BINARY INPUT
ANALOG OUTPUT
MSB
LSB
1111 1111 1111
1000 0000 0000
0000 0000 0001
0000 0000 0000
–VREF (4095/4096)
–VREF (2048/4096)
–VREF (1/4096)
0V
TABLE I. Unipolar Codes.
C1 phase compensation (10 to 25pF) in Figure 4 may be
required for stability when using high speed amplifiers. C1
is used to cancel the pole formed by the DAC internal
feedback resistance and output capacitance at Out1.
R1 in Figure 5 provides full scale trim capability—load the
DAC register to 1111 1111 1111, adjust R1 for VOUT = –
VREF (4095/4096). Alternatively, full scale can be adjusted
by omitting R1 and R2 and trimming the reference voltage
magnitude.
APPLICATIONS
OP AMP CONSIDERATIONS
The input bias current of the op amp flows through the
feedback resistor, creating an error voltage at the output of
the op amp. This will show up as an offset through all codes
of the transfer characteristics. A low bias current op amp
such as the OPA606 is recommended.
Low offset voltage and VOS drift are also important. The
output impedance of the DAC is modulated with the digital
code. This impedance change (approximately 10kΩ to 30kΩ)
is a change in closed-loop gain to the op amp. The result is
that VOS will be multiplied by a factor of one to two
depending on the code. This shows up as a linearity error.
Offset can be adjusted out using Figure 4. Gain may be
adjusted using Figure 5.
BIPOLAR FOUR-QUADRANT OPERATION
Figure 6 shows the connections for bipolar four-quadrant
operation. Offset can be adjusted with the A1 to A2 summing
resistor, with the input code set to 1000 0000 0000. Gain
may be adjusted by varying the feedback resistor of A2. The
input/output relationship is shown in Table II.
UNIPOLAR BINARY OPERATION
(Two-Quadrant Multiplication)
Figure 4 shows the analog circuit connections required for
unipolar binary (two-quadrant multiplication) operation. With
a DC reference voltage or current (positive or negative
polarity) applied at pin 17, the circuit is a unipolar D/A
converter. With an AC reference voltage or current, the
circuit provides two-quadrant multiplication (digitally controlled attenuation). The input/output relationship is shown
in Table I.
BINARY INPUT
ANALOG OUTPUT
MSB
LSB
1111 1111 1111
1000 0000 0000
0111 1111 1111
0000 0000 0000
+VREF (2047/2048)
0V
–VREF (1/2048)
–VREF (2048/2048)
TABLE II. Bipolar Codes.
®
DAC7541A
55pF
6
MSB
B1 •
•
•
•
•
•
•
•
•
• B12
VOUT = –VREF
16
17
4
5
6
7
8
9
10 11 12 13 14 15
C1
RF 18
1
+15V
DAC7541A
Out1
Out2
VREF
B1
2
+
B2
4
+
B3
8
+•••+
B12
4096
)
–10V ≤ VREF ≤ +10V
VOUT
OPA604
2
(
3
0 ≤ VOUT ≤ –
4095
V
4096 REF
Where: BN = 1 if the BN digital input is HIGH.
BN = 0 if the BN digital input is LOW.
10kΩ
Single-Point Ground
+VCC
FIGURE 4. Basic Connection With Op Amp VOS Adjust: Unipolar (two-quadrant) Multiplying Configuration.
MSB
B1 •
4
16
•
5
•
6
•
7
•
8
•
9
•
•
•
R1
200Ω
• B12
18
1
+15V
DAC7541A
17
R2
200kΩ
10 11 12 13 14 15
OPA604
VREF
2
3
10kΩ
+VCC
FIGURE 5. Basic Connection With Gain Adjust (allows adjustment up or down).
47Ω
+VDD
16
18
1
VREF
17
20kΩ
10kΩ
A1
DAC7541A
4...15
20kΩ
OPA604
or
1/2 OPA2604
C1
33pF
VOUT
A2
2
3
5kΩ
OPA604
or
1/2 OPA2604
Bits 1-12
VOUT = +VREF
(
B1
1
+
B2
2
+
B3
4
+•••+
B12
2048
)
–1
FIGURE 6. Bipolar Four-Quadrant Multiplier.
®
7
DAC7541A
DIGITALLY CONTROLLED GAIN BLOCK
The DAC7541A may be used in a digitally controlled gain
block as shown in Figure 7. This circuit gives a range of gain
from one (all bits = one) to 4096 (LSB = one). The transfer
function is:
–VIN
VOUT =
B1
B2
B3
B12
+
+
+•••+
2
4
8
4096
(
Bits 1 to 12
VIN
18
16
VDD
DAC7541A
)
1
17
2
All bits off is an illegal state, as division by zero is impossible (no op amp feedback). Also, errors increase as gain
increases, and errors are minimized at major carries (only
one bit on at a time).
3
VOUT
OPA604
FIGURE 7. Digitally Programmable Gain Block.
®
DAC7541A
8
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