AD AD7541ASQ Cmos 12-bit monolithic multiplying dac Datasheet

a
CMOS
12-Bit Monolithic Multiplying DAC
AD7541A
FEATURES
Improved Version of AD7541
Full Four-Quadrant Multiplication
12-Bit Linearity (Endpoint)
All Parts Guaranteed Monotonic
TTL/CMOS Compatible
Low Cost
Protection Schottky Diodes Not Required
Low Logic Input Leakage
FUNCTIONAL BLOCK DIAGRAM
10kΩ
10kΩ
10kΩ
VREF
20kΩ
S1
20kΩ
20kΩ
S2
S3
20kΩ
20kΩ
S12
OUT2
OUT1
10kΩ
RFEEDBACK
GENERAL DESCRIPTION
BIT 1 (MSB)
BIT 2
BIT 3
BIT 12 (LSB)
The Analog Devices AD7541A is a low cost, high performance
12-bit monolithic multiplying digital-to-analog converter. It is
fabricated using advanced, low noise, thin film on CMOS
technology and is available in a standard 18-lead DIP and in
20-terminal surface mount packages.
PRODUCT HIGHLIGHTS
The AD7541A is functionally and pin compatible with the industry standard AD7541 device and offers improved specifications and performance. The improved design ensures that the
device is latch-up free so no output protection Schottky diodes
are required.
Compatibility: The AD7541A can be used as a direct replacement for any AD7541-type device. As with the Analog Devices
AD7541, the digital inputs are TTL/CMOS compatible and
have been designed to have a ± 1 µA maximum input current
requirement so as not to load the driving circuitry.
This new device uses laser wafer trimming to provide full 12-bit
endpoint linearity with several new high performance grades.
Improvements: The AD7541A offers the following improved
specifications over the AD7541:
DIGITAL INPUTS (DTL/TTL/CMOS COMPATIBLE)
LOGIC: A SWITCH IS CLOSED TO IOUT1 FOR
ITS DIGITAL INPUT IN A "HIGH" STATE.
1. Gain Error for all grades has been reduced with premium
grade versions having a maximum gain error of ± 3 LSB.
ORDERING GUIDE 1
Model2
Temperature
Range
Relative
Gain
Accuracy
Error
TMIN to T MAX TA = +258C
Package
Options3
AD7541AJN
AD7541AKN
AD7541AJP
AD7541AKP
AD7541AKR
AD7541AAQ
AD7541ABQ
AD7541ASQ
AD7541ATQ
AD7541ASE
AD7541ATE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
–25°C to +85°C
–25°C to +85°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
± 1 LSB
± 1/2 LSB
± 1 LSB
± 1/2 LSB
± 1/2 LSB
± 1 LSB
± 1/2 LSB
± 1 LSB
± 1/2 LSB
± 1 LSB
± 1/2 LSB
N-18
N-18
P-20A
P-20A
R-18
Q-18
Q-18
Q-18
Q-18
E-20A
E-20A
± 6 LSB
± 1 LSB
±6
±1
±1
± 6 LSB
± 1 LSB
± 6 LSB
± 1 LSB
± 6 LSB
± 1 LSB
2. Gain Error temperature coefficient has been reduced to
2 ppm/°C typical and 5 ppm/°C maximum.
3. Digital-to-analog charge injection energy for this new device
is typically 20% less than the standard AD7541 part.
4. Latch-up proof.
5. Improvements in laser wafer trimming provides 1/2 LSB max
differential nonlinearity for top grade devices over the operating temperature range (vs. 1 LSB on older 7541 types).
6. All grades are guaranteed monotonic to 12 bits over the
operating temperature range.
NOTES
1
Analog Devices reserves the right to ship either ceramic (D-18) or cerdip (Q-18)
hermetic packages.
2
To order MIL-STD-883, Class B process parts, add /883B to part number. Contact
local sales office for military data sheet.
3
E = Leadless Ceramic Chip Carrier; N = Plastic DIP; P = Plastic Leaded Chip
Carrier; Q = Cerdip; R = Small Outline IC.
REV. B
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: 617/329-4700
World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 1997
AD7541A–SPECIFICATIONS (V
DD
= +15 V, VREF = +10 V; OUT 1 = OUT 2 = GND = 0 V unless otherwise noted)
Version
TA =
+258C
TA =
TMIN, TMAX1
Units
All
J, A, S
K, B, T
J, A, S
K, B, T
J, A, S
K, B, T
12
±1
± 1/2
±1
± 1/2
±6
±3
12
±1
± 1/2
±1
± 1/2
±8
±5
Bits
LSB max
LSB max
LSB max
LSB max
LSB max
LSB max
All
5
5
ppm/°C max
Typical Value Is 2 ppm/°C.
J, K
A, B
S, T
J, K
A, B
S, T
±5
±5
±5
±5
±5
±5
± 10
± 10
± 200
± 10
± 10
± 200
nA max
nA max
nA max
nA max
nA max
nA max
All Digital Inputs = 0 V.
REFERENCE INPUT
Input Resistance (Pin 17 to GND)
All
7–18
7–18
kΩ min/max
Typical Input Resistance = 11 kΩ.
Typical Input Resistance Temperature
Coefficient = –300 ppm/°C.
DIGITAL INPUTS
VIH (Input HIGH Voltage)
VIL (Input LOW Voltage)
I IN (Input Current)
CIN (Input Capacitance) 2
All
All
All
All
2.4
0.8
±1
8
2.4
0.8
±1
8
V min
V max
µA max
pF max
Logic Inputs Are MOS Gates. IIN typ (25°C) = 1 nA.
VIN = 0 V
POWER SUPPLY REJECTION
DGain/DVDD
All
± 0.01
± 0.02
% per % max
DVDD = ± 5%
POWER SUPPLY
VDD Range
I DD
All
All
+5 to +16
2
100
+5 to +16
2
500
V min/V max
mA max
µA max
Accuracy Is Not Guaranteed Over This Range.
All Digital Inputs VIL or V IH.
All Digital Inputs 0 V or VDD .
Parameter
ACCURACY
Resolution
Relative Accuracy
Differential Nonlinearity
Gain Error
Gain Temperature Coefficient2
DGain/DTemperature
Output Leakage Current
OUT1 (Pin 1)
OUT2 (Pin 2)
Test Conditions/Comments
± 1 LSB = ±0.024% of Full Scale
± 1/2 LSB = ± 0.012% of Full Scale
All Grades Guaranteed Monotonic
to 12 Bits, TMIN to TMAX.
Measured Using Internal RFB and Includes
Effect of Leakage Current and Gain TC.
Gain Error Can Be Trimmed to Zero.
All Digital Inputs = VDD .
AC PERFORMANCE CHARACTERISTICS
These Characteristics are included for Design Guidance only and are not subject to test. VDD = +15 V, VIN = +10 V except where noted,
OUT1 = 0UT2 = GND = 0 V, Output Amp is AD544 except where noted.
Parameter
Version1
PROPAGATION DELAY (From Digital Input
Change to 90% of Final Analog Output)
All
TA =
+258C
100
TA =
TMIN, TMAX1
—
Units
ns typ
OUT 1 Load = 100 Ω, CEXT = 13 pF.
Digital Inputs = 0 V to VDD or VDD to 0 V.
nV-sec typ
VREF = 0 V. All digital inputs 0 V to VDD or
VDD to 0 V.
Measured using Model 50K as output amplifier.
DIGITAL TO ANALOG GLITCH
IMPULSE
All
1000
—
Test Conditions/Comments
3
MULTIPLYING FEEDTHROUGH ERROR
(VREF to OUT1)
All
1.0
—
mV p-p typ
VREF = ± 10 V, 10 kHz sine wave.
OUTPUT CURRENT SETTLING TIME
All
0.6
—
µs typ
To 0.01% of full-scale range.
OUT 1 Load = 100 Ω, CEXT = 13 pF.
Digital Inputs = 0 V to VDD or VDD to 0 V.
OUTPUT CAPACITANCE
COUT1 (Pin 1)
COUT2 (Pin 2)
COUT1 (Pin 1)
COUT2 (Pin 2)
All
All
All
All
200
70
70
200
200
70
70
200
pF max
pF max
pF max
pF max
Digital Inputs
= VIH
Digital Inputs
= VIL
NOTES
1
Temperature range as follows: J, K versions, 0°C to +70°C; A, B versions, –25°C to +85°C; S, T versions, –55°C to +125°C.
2
Guaranteed by design but not production tested.
3
To minimize feedthrough in the ceramic package (Suffix D) the user must ground the metal lid.
Specifications subject to change without notice.
–2–
REV. B
AD7541A
Operating Temperature Range
Commercial (J, K Versions) . . . . . . . . . . . . . 0°C to +70°C
Industrial (A, B Versions) . . . . . . . . . . . . . –25°C to +85°C
Extended (S, T Versions) . . . . . . . . . . . . . –55°C to +125°C
Storage Temperature . . . . . . . . . . . . . . . . . . –65°C to +150°C
Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . +300°C
ABSOLUTE MAXIMUM RATINGS*
(TA = +25°C unless otherwise noted)
VDD to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +17 V
VREF to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 25 V
VRFB to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 25 V
Digital Input Voltage to GND . . . . . . . . –0.3 V, VDD + 0.3 V
OUT 1, OUT 2 to GND . . . . . . . . . . . . –0.3 V, VDD + 0.3 V
Power Dissipation (Any Package)
To +75°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 mW
Derates above +75°C . . . . . . . . . . . . . . . . . . . . . . 6 mW/°C
*Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions 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.
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 AD7541A 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.
WARNING!
ESD SENSITIVE DEVICE
TERMINOLOGY
OUTPUT LEAKAGE CURRENT
RELATIVE ACCURACY
Current which appears at OUTI with the DAC loaded to all 0s
or at OUT2 with the DAC loaded to all 1s.
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 expressed in % of fullscale range or (sub)multiples of 1 LSB.
AC error due to capacitive feedthrough from VREF terminal to
OUT1 with DAC loaded to all 0s.
DIFFERENTIAL NONLINEARITY
OUTPUT CURRENT SETTLING TIME
Differential nonlinearity is the difference between the measured
change and the ideal l LSB change between any two adjacent
codes. A specified differential nonlinearity of ±1 LSB max over
the operating temperature range insures monotonicity.
Time required for the output function of the DAC to settle to
within 1/2 LSB for a given digital input stimulus, i.e., 0 to full
scale.
MULTIPLYING FEEDTHROUGH ERROR
PROPAGATION DELAY
This is a measure of the internal delay of the circuit and is measured from the time a digital input changes to the point at which
the analog output at OUT1 reaches 90% of its final value.
GAIN ERROR
Gain error is a measure of the output error between an ideal
DAC and the actual device output. For the AD7541A, ideal
maximum output is
DIGITAL-TO-ANALOG CHARGE INJECTION (QDA)
 4095 
–  4096  (VREF ).


Gain error is adjustable to zero using external trims as shown in
Figures 4, 5 and 6.
This is a measure of the amount of charge injected from the
digital inputs to the analog outputs when the inputs change
state. It is usually specified as the area of the glitch in nV secs
and is measured with VREF = GND and a Model 50K as the
output op amp, C1 (phase compensation) = 0 pF.
PIN CONFIGURATIONS
12 BIT 9
BIT 5 8
11 BIT 8
BIT 6 9
10 BIT 7
REV. B
BIT 3 7
16 BIT 11
15 BIT 10
14 BIT 9
BIT 4 8
NC
RFB
VREF
OUT 2
OUT 1
VREF
RFB
NC
TOP VIEW
(Not to Scale)
20 19
PIN 1
IDENTIFIER
GND 4
BIT 1 (MSB) 5
16 BIT 11
TOP VIEW
(Not to Scale)
BIT 3 7
15 BIT 10
BIT 4 8
9 10 11 12 13
NC = NO CONNECT
–3–
14 BIT 9
9
NC = NO CONNECT
18 VDD
17 BIT 12 (LSB)
AD7541A
BIT 2 6
10 11 12 13
BIT 8
BIT 4 7
BIT 2 6
1
NC
TOP VIEW 14 BIT 11
(Not to Scale)
BIT 3 6
13 BIT 10
17 BIT 12 (LSB)
AD7541A
2
BIT 7
BIT 2 5
18 VDD
GND 4
BIT 1 (MSB) 5
3
BIT 5
15 BIT 12 (LSB)
PLCC
BIT 6
AD7541A
1 20 19
BIT 8
BIT 1 (MSB) 4
2
NC
16 VDD (+)
3
BIT 7
GND 3
OUT 2
17 VREF IN
BIT 6
18 RFEEDBACK
OUT2 2
BIT 5
OUT1 1
LCCC
OUT 1
DIP/SOIC
AD7541A
APPLICATIONS
GENERAL CIRCUIT INFORMATION
The simplified D/A circuit is shown in Figure 1. An inverted
R-2R ladder structure is used—that is, the binarily weighted
currents are switched between the OUT1 and OUT2 bus lines,
thus maintaining a constant current in each ladder leg independent of the switch state.
10kΩ
10kΩ
UNIPOLAR BINARY OPERATION
(2-QUADRANT MULTIPLICATION)
Figure 4 shows the analog circuit connections required for unipolar binary (2-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 2-quadrant
multiplication (digitally controlled attenuation). The input/
output relationship is shown in Table II.
10kΩ
VREF
20kΩ
S1
20kΩ
20kΩ
S2
S3
20kΩ
20kΩ
S12
R1 provides full-scale trim capability [i.e., 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.
OUT2
OUT1
10kΩ
RFEEDBACK
BIT 1 (MSB)
BIT 2
BIT 3
C1 phase compensation (10 pF to 25 pF) 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).
BIT 12 (LSB)
DIGITAL INPUTS (DTL/TTL/CMOS COMPATIBLE)
LOGIC: A SWITCH IS CLOSED TO IOUT1 FOR
ITS DIGITAL INPUT IN A "HIGH" STATE.
Amplifier A1 should be selected or trimmed to provide VOS ≤
10% of the voltage resolution at VOUT. Additionally, the amplifier should exhibit a bias current which is low over the temperature range of interest (bias current causes output offset at VOUT
equal to IB times the DAC feedback resistance, nominally 11 kΩ).
The AD544L is a high speed implanted FET input op amp with
low factory-trimmed VOS.
Figure 1. Functional Diagram (Inputs HIGH)
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 V REF 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. (If a current
source is used, a low temperature coefficient external RFB is
recommended to define scale factor.)
VDD
EQUIVALENT CIRCUIT ANALYSIS
The equivalent circuits for all digital inputs LOW and all digital
inputs HIGH are shown in Figures 2 and 3. In Figure 2 with all
digital inputs LOW, the reference current is switched to OUT2.
The current source ILEAKAGE is composed of surface and junction leakages to the substrate, while the I/4096 current source
represents a constant 1-bit current drain through the termination resistor on the R-2R ladder. The ON capacitance of the
output N-channel switch is 200 pF, as shown on the OUT2
terminal. The OFF switch capacitance is 70 pF, as shown on
the OUT1 terminal. Analysis of the circuit for all digital inputs
HIGH, as shown in Figure 3 is similar to Figure 2; however, the
ON switches are now on terminal OUT1, hence the 200 pF at
that terminal.
VIN
R1*
R
ILEAKAGE
200pF
OUT2
JN/AQ/SD
KN/BQ/TD
R1
R2
100 Ω
47 Ω
100 Ω
33 Ω
ILEAKAGE
200pF
ILEAKAGE
70pF
1111
1111
 4095 
–VIN 

 4096 
1000
0000
0000
 2048 
–VIN  4096  = –1/2 VIN


0000
0000
0001
0000
0000
0000
 1 
–VIN 

 4096 
0 Volts
OUT2
Figure 3. DAC Equivalent Circuit All Digital Inputs HIGH
–4–
Analog Output, VOUT
1111
R
I/4096
ANALOG
COMMON
Trim
Resistor
OUT1
IREF
DIGITAL
GROUND
Table II. Unipolar Binary Code Table for Circuit of Figure 4
RFB
15kΩ
AD544L
(SEE TEXT)
3
Figure 2. DAC Equivalent Circuit All Digital Inputs LOW
R
2
DGND
Binary Number in DAC
MSB
LSB
VREF
VOUT
Table I. Recommended Trim Resistor Values vs. Grades
OUT2
I/4096
OUT1 1
AD7541A
Figure 4. Unipolar Binary Operation
15kΩ
IREF
17 VREF
C1
33pF
*REFER TO TABLE 1
OUT1
VREF
18
RFB
BIT 1 – BIT 12
R
70pF
16
VDD
PINS 4–15
RFB
ILEAKAGE
R2*
REV. B
AD7541A
BIPOLAR OPERATION
(4-QUADRANT MULTIPLICATION)
Figure 5 and Table III illustrate the circuitry and code relationship for bipolar operation. With a dc reference (positive or negative polarity) the circuit provides offset binary operation. With
an ac reference the circuit provides full 4-quadrant multiplication.
With the DAC loaded to 1000 0000 0000, adjust R1 for
VOUT = 0 V (alternatively, one can omit R1 and R2 and adjust
the ratio of R3 to R4 for VOUT = 0 V). Full-scale trimming can
be accomplished by adjusting the amplitude of VREF or by varying the value of R5.
Figure 6 and Table IV show an alternative method of achieving
bipolar output. The circuit operates with sign plus magnitude
code and has the advantage of giving 12-bit resolution in each
quadrant, compared with 11-bit resolution per quadrant for the
circuit of Figure 5. The AD7592 is a fully protected CMOS
changeover switch with data latches. R4 and R5 should match
each other to 0.01% to maintain the accuracy of the D/A converter. Mismatch between R4 and R5 introduces a gain error.
VDD
R2*
16
VDD
As in unipolar operation, A1 must be chosen for low VOS and
low IB . R3, R4 and R5 must be selected for matching and tracking. Mismatch of 2R3 to R4 causes both offset and full-scale
error. Mismatch of R5 to R4 or 2R3 causes full-scale error. C1
phase compensation (10 pF to 50 pF) may be required for stability, depending on amplifier used.
VIN
R1*
17 VREF
RFB
OUT1 1
AD7541A
PINS 4–15
SIGN BIT
R2*
16
VDD
VIN
R1*
17 VREF
RFB
R5
20kΩ
AD544L
R6
5kΩ
A2
DIGITAL
GROUND
ANALOG
COMMON
10%
ANALOG
COMMON
BIT 1 – BIT 12
DIGITAL
GROUND
Binary Number in DAC
MSB
LSB
0
1111 1111 1111
 4095 
+V IN ×  4096 


0
0000 0000 0000
0 Volts
1
0000 0000 0000
0 Volts
1
1111 1111 1111
 4095 
–VIN × 

 4096 
*FOR VALUES OF R1 AND R2
SEE TABLE 1.
Table III. Bipolar Code Table for Offset Binary Circuit of
Figure 5
Analog Output, VOUT
Note: Sign bit of “0” connects R3 to GND.
 2047 
 2048 


1111
1111
1111
+VIN
1000
0000
0001
1000
0000
0000
 1 
+VIN 

 2048 
0 Volts
0111
1111
1111
 1 
–VIN  2048 


0000
0000
0000
 2048 
–VIN  2048 


REV. B
SEE TABLE 1.
Sign
Bit
Figure 5. Bipolar Operation (4-Quadrant Multiplication)
Binary Number in DAC
MSB
LSB
*FOR VALUES OF R1 AND R2
VOUT
AD544J
3
AD544J
1/2 AD7592JN
Table IV. 12-Bit Plus Sign Magnitude Code Table for Circuit
of Figure 6
A1
OUT2 2
GND
10%
AD544L
3
VOUT
A2
Figure 6. 12-Bit Plus Sign Magnitude Operation
R3
10kΩ
OUT1 1
AD7541A
PINS 4–15
R4
20kΩ
C1
33pF
18
R5
20kΩ
R3
10kΩ
A1
OUT2 2
GND
BIT 1 – BIT 12
VDD
R4
20kΩ
C1
33pF
18
–5–
Analog Output, VOUT
AD7541A
SINGLE SUPPLY OPERATION
Figure 7 shows the AD7541A connected in a voltage switching
mode. OUT1 is connected to the reference voltage and OUT2
is connected to GND. The D/A converter output voltage is
available at the VREF pin (Pin 17) and has a constant output
impedance equal to RLDR. The feedback resistor RFB is not used
in this circuit.
APPLICATIONS HINTS
Output Offset: CMOS D/A converters exhibit a code-dependent
output resistance which in turn can cause a code-dependent
error voltage at the output of the amplifier. The maximum amplitude of this offset, which adds to the D/A converter nonlinearity, is 0.67 VOS where VOS is the amplifier input offset
voltage. To maintain monotonic operation it is recommended
that VOS be no greater than (25 × 10–6) (VREF) over the temperature range of operation. Suitable op amps are AD517L and
AD544L. The AD517L is best suited for fixed reference applications with low bandwidth requirements: it has extremely low
offset (50 µV) and in most applications will not require an offset
trim. The AD544L has a much wider bandwidth and higher
slew rate and is recommended for multiplying and other applications requiring fast settling. An offset trim on the AD544L
may be necessary in some circuits.
VDD = +15V
NOT
USED
1
VREF
+2.5V
OUT1
18
16
RFB
VDD
AD7541A
2
OUT2
GND
3
CA3140B
VOUT = 0V TO +10V
PINS 4–15
4
V–
15
R1
10kΩ
Digital Glitches: One cause of digital glitches is capacitive
coupling from the digital lines to the OUT1 and OUT2 terminals. This should be minimized by screening the analog pins of
the AD7541A (Pins 1, 2, 17, 18) from the digital pins by a
ground track run between Pins 2 and 3 and between Pins 16
and 17 of the AD7541A. Note how the analog pins are at one
end of the package and separated from the digital pins by VDD
and GND to aid screening at the board level. On-chip capacitive
coupling can also give rise to crosstalk from the digital-to-analog
sections of the AD7541A, particularly in circuits with high currents and fast rise and fall times.
V+
VREF 17
R2
30kΩ
BIT 1 – BIT 12
VOUT ±V REF D (1 +R2/R1) WHERE 0 ≤ D ≤ 1
i.e., D IS A FRACTIONAL REPRESENTATION OF THE DIGITAL INPUT
SYSTEM
GROUND
Figure 7. Single Supply Operation Using Voltage Switching Mode
The reference voltage must always be positive. If OUT1 goes
more than 0.3 V less than GND, an internal diode will be turned
on and a heavy current may flow causing device damage (the
AD7541A is, however, protected from the SCR latch-up
phenomenon prevalent in many CMOS devices). Suitable references include the AD580 and AD584.
Temperature Coefficients: The gain temperature coefficient
of the AD7541A has a maximum value of 5 ppm/°C and a typical value of 2 ppm/°C. This corresponds to worst case gain shifts
of 2 LSBs and 0.8 LSBs, respectively, over a 100°C temperature
range. When trim resistors R1 and R2 are used to adjust fullscale range, the temperature coefficient of R1 and R2 should
also be taken into account. The reader is referred to Analog
Devices Application Note “Gain Error and Gain Temperature
Coefficient of CMOS Multiplying DACs,” Publication Number
E630c-5-3/86.
The loading on the reference voltage source is code-dependent
and the response time of the circuit is often determined by the
behavior of the reference voltage with changing load conditions.
To maintain linearity, the voltage at OUT1 should remain within
2.5 V of GND, for a V DD of 15 V. If VDD is reduced from 15 V
or the reference voltage at OUT1 increased to more than 2.5 V,
the differential nonlinearity of the DAC will increase and the
linearity of the DAC will be degraded.
SUPPLEMENTAL APPLICATION MATERIAL
For further information on CMOS multiplying D/A converters,
the reader is referred to the following texts:
CMOS DAC Application Guide, Publication Number
G872b-8-1/89 available from Analog Devices.
Gain Error and Gain Temperature Coefficient of CMOS
Multiplying DACs Application Note, Publication Number
E630c-5-3/86 available from Analog Devices.
Analog-Digital Conversion Handbook—available from Analog
Devices.
–6–
REV. B
AD7541A
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
20-Terminal Ceramic Leadless Chip Carrier
(E-20A)
0.075
(1.91)
REF
0.100 (2.54)
0.064 (1.63)
0.095 (2.41)
0.075 (1.90)
0.358 (9.09) 0.358
(9.09)
0.342 (8.69)
MAX
SQ
SQ
0.200 (5.08)
BSC
0.015 (0.38)
MIN
3
4
1
0.055 (1.40)
0.045 (1.14)
0.056 (1.42)
0.042 (1.07)
19
18
PIN 1
IDENTIFIER
TOP VIEW
(PINS DOWN)
8
0.050 (1.27)
BSC
8
0.150 (3.81)
BSC
0.005 (0.13) MIN
1
9
PIN 1
0.022 (0.558)
0.014 (0.356)
0.070 (1.77)
0.045 (1.15)
10
0.310 (7.87)
0.220 (5.59)
0.325 (8.25)
0.300 (7.62) 0.195 (4.95)
0.115 (2.93)
1
9
PIN 1
0.960 (24.38) MAX
0.200 (5.08)
MAX
0.130
(3.30)
MIN
0.100
(2.54)
BSC
0.098 (2.49) MAX
18
0.280 (7.11)
0.240 (6.10)
0.060 (1.52)
0.015 (0.38)
0.210
(5.33)
MAX
0.160 (4.06)
0.115 (2.93)
0.200 (5.08)
0.125 (3.18)
0.023 (0.58)
0.014 (0.36)
0.015 (0.381)
0.008 (0.204)
SEATING
PLANE
0.100
(2.54)
BSC
1
9
PIN 1
0.0118 (0.30)
0.0040 (0.10)
0.4193 (10.65)
0.3937 (10.00)
10
0.2992 (7.60)
0.2914 (7.40)
0.4625 (11.75)
0.4469 (11.35)
18
0.1043 (2.65)
0.0926 (2.35)
0.0291 (0.74)
x 45°
0.0098 (0.25)
8°
0.0500 0.0192 (0.49)
0°
(1.27) 0.0138 (0.35) SEATING 0.0125 (0.32)
PLANE
BSC
0.0091 (0.23)
–7–
0.060 (1.52)
0.015 (0.38)
0.320 (8.13)
0.290 (7.37)
0.150
(3.81)
MIN
18-Lead SOIC
(R-18)
REV. B
0.110 (2.79)
0.085 (2.16)
18-Lead Cerdip
(Q-18)
0.925 (23.49)
0.845 (21.47)
10
0.040 (1.01)
0.025 (0.64)
0.356 (9.04)
SQ
0.350 (8.89)
0.395 (10.02)
SQ
0.385 (9.78)
18-Lead Plastic DIP
(N-18)
18
0.021 (0.53)
0.013 (0.33) 0.330 (8.38)
0.032 (0.81) 0.290 (7.37)
0.026 (0.66)
0.050
(1.27)
BSC
14
13
9
0.020
(0.50)
R
9
0.025 (0.63)
0.015 (0.38)
3
4
0.028 (0.71)
0.022 (0.56)
BOTTOM
VIEW
14
13
0.048 (1.21)
0.042 (1.07)
45° TYP
0.088 (2.24)
0.054 (1.37)
0.180 (4.57)
0.165 (4.19)
0.048 (1.21)
0.042 (1.07)
0.100 (2.54) BSC
19
18 20
0.011 (0.28)
0.007 (0.18)
R TYP
0.075 (1.91)
REF
20-Lead Plastic Leadless Chip Carrier
(P-20A)
0.0500 (1.27)
0.0157 (0.40)
0.070 (1.78) SEATING
0.030 (0.76) PLANE
15°
0°
0.015 (0.38)
0.008 (0.20)
–8–
PRINTED IN U.S.A.
C718b–1–6/97