Datenblatt-pdf.com


AD7528 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD7528
Beschreibung CMOS Dual 8-Bit Buffered Multiplying DAC
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 8 Seiten
AD7528 Datasheet, Funktion
a
FEATURES
On-Chip Latches for Both DACs
+5 V to +15 V Operation
DACs Matched to 1%
Four Quadrant Multiplication
TTL/CMOS Compatible
Latch Free (Protection Schottkys not Required)
APPLICATIONS
Digital Control of:
Gain/Attenuation
Filter Parameters
Stereo Audio Circuits
X-Y Graphics
CMOS Dual 8-Bit
Buffered Multiplying DAC
AD7528
VDD
DB0
DATA
INPUTS
DB7
FUNCTIONAL BLOCK DIAGRAM
VREF A
INPUT
BUFFER
LATCH
DAC A
DAC A/
DAC B
CS
WR
DGND
CONTROL
LOGIC
AD7528
LATCH
DAC B
RFB A
OUT A
AGND
RFB B
OUT B
GENERAL DESCRIPTION
The AD7528 is a monolithic dual 8-bit digital/analog converter
featuring excellent DAC-to-DAC matching. It is available in
skinny 0.3" wide 20-lead DIPs and in 20-lead surface mount
packages.
Separate on-chip latches are provided for each DAC to allow
easy microprocessor interface.
Data is transferred into either of the two DAC data latches via a
common 8-bit TTL/CMOS compatible input port. Control
input DAC A/DAC B determines which DAC is to be loaded.
The AD7528’s load cycle is similar to the write cycle of a ran-
dom access memory and the device is bus compatible with most
8-bit microprocessors, including 6800, 8080, 8085, Z80.
The device operates from a +5 V to +15 V power supply, dis-
sipating only 20 mW of power.
Both DACs offer excellent four quadrant multiplication charac-
teristics with a separate reference input and feedback resistor for
each DAC.
PRODUCT HIGHLIGHTS
1. DAC-to-DAC matching: since both of the AD7528 DACs are
fabricated at the same time on the same chip, precise match-
ing and tracking between DAC A and DAC B is inherent.
The AD7528’s matched CMOS DACs make a whole new
range of applications circuits possible, particularly in the
audio, graphics and process control areas.
2. Small package size: combining the inputs to the on-chip DAC
latches into a common data bus and adding a DAC A/DAC B
select line has allowed the AD7528 to be packaged in either a
small 20-lead DIP, SOIC or PLCC.
VREF B
ORDERING GUIDE1
Model2
Temperature
Ranges
Relative Gain Package
Accuracy Error Options3
AD7528JN
AD7528KN
AD7528LN
AD7528JP
AD7528KP
AD7528LP
AD7528JR
AD7528KR
AD7528LR
AD7528AQ
AD7528BQ
AD7528CQ
AD7528SQ
AD7528TQ
AD7528UQ
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
±1 LSB
±1/2 LSB
±1/2 LSB
±1 LSB
±1/2 LSB
±1/2 LSB
±1 LSB
±1/2 LSB
±1/2 LSB
±1 LSB
±1/2 LSB
±1/2 LSB
±1 LSB
±1/2 LSB
±1/2 LSB
±4 LSB
±2 LSB
±1 LSB
±4 LSB
±2 LSB
±1 LSB
±4 LSB
±2 LSB
±1 LSB
±4 LSB
±2 LSB
±1 LSB
±4 LSB
±2 LSB
±1 LSB
N-20
N-20
N-20
P-20A
P-20A
P-20A
R-20
R-20
R-20
Q-20
Q-20
Q-20
Q-20
Q-20
Q-20
NOTES
1Analog Devices reserves the right to ship side-brazed ceramic in lieu of cerdip. Parts
will be marked with cerdip designator “Q.”
2Processing to MIL-STD-883C, Class B is available. To order, add suffix “/883B” to
part number. For further information, see Analog Devices’ 1990 Military Products
Databook.
3N = Plastic DIP; P = Plastic Leaded Chip Carrier; Q = Cerdip; R = SOIC.
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: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1998






AD7528 Datasheet, Funktion
AD7528
APPLICATIONS INFORMATION
Application Hints
To ensure system performance consistent with AD7528 specifi-
cations, careful attention must be given to the following points:
1. GENERAL GROUND MANAGEMENT: AC or transient
voltages between the AD7528 AGND and DGND can cause
noise injection into the analog output. The simplest method
of ensuring that voltages at AGND and DGND are equal is
to tie AGND and DGND together at the AD7528. In more
complex systems where the AGND–DGND intertie is on the
backplane, it is recommended that diodes be connected in
inverse parallel between the AD7528 AGND and DGND
pins (1N914 or equivalent).
2. OUTPUT AMPLIFIER OFFSET: CMOS DACs exhibit a
code-dependent output resistance which in turn causes a
code-dependent amplifier noise gain. The effect is a code-
dependent differential nonlinearity term at the amplifier
output which depends on VOS (VOS is amplifier input offset
voltage). This differential nonlinearity term adds to the R/2R
differential nonlinearity. To maintain monotonic operation, it
is recommended that amplifier VOS be no greater than 10% of
1 LSB over the temperature range of interest.
3. HIGH FREQUENCY CONSIDERATIONS: The output
capacitance of a CMOS DAC works in conjunction with the
amplifier feedback resistance to add a pole to the open loop
response. This can cause ringing or oscillation. Stability can
be restored by adding a phase compensation capacitor in
parallel with the feedback resistor.
DYNAMIC PERFORMANCE
The dynamic performance of the two DACs in the AD7528 will
depend upon the gain and phase characteristics of the output
amplifiers together with the optimum choice of the PC board
layout and decoupling components. Figure 6 shows the relation
–100
–90
–80
–70
–60
TA = +25؇C
VDD = +15V
VIN = 20V PEAK TO PEAK
ship between input frequency and channel to channel isolation.
Figure 7 shows a printed circuit layout for the AD7528 and the
AD644 dual op amp which minimizes feedthrough and crosstalk.
SINGLE SUPPLY APPLICATIONS
The AD7528 DAC R-2R ladder termination resistors are con-
nected to AGND within the device. This arrangement is par-
ticularly convenient for single supply operation because AGND
may be biased at any voltage between DGND and VDD. Figure
8 shows a circuit which provides two +5 V to +8 V analog out-
puts by biasing AGND +5 V up from DGND. The two DAC
reference inputs are tied together and a reference input voltage
is obtained without a buffer amplifier by making use of the
constant and matched impedances of the DAC A and DAC B
reference inputs. Current flows through the two DAC R-2R
ladders into R1 and R1 is adjusted until the VREF A and VREF B
inputs are at +2 V. The two analog output voltages range from
+5 V to +8 V for DAC codes 00000000 to 11111111.
VDD = +15V
DATA
INPUTS
CS
WR
DAC A/DAC B
2 VOLTS
R1
10k
R2
1k
DAC A
DB0
DB7
AD7528
DAC B
VOUT A = +5V TO +8V
SUGGESTED
OP AMP:
AD644
VOUT B = +5V TO +8V
AD584J
VDD
GND
Figure 8. AD7528 Single Supply Operation
Figure 9 shows DAC A of the AD7528 connected in a positive
reference, voltage switching mode. This configuration is useful
in that VOUT is the same polarity as VIN allowing single supply
operation. However, to retain specified linearity, VIN must be in
the range 0 V to +2.5 V and the output buffered or loaded with
a high impedance, see Figure 10. Note that the input voltage is
connected to the DAC OUT A and the output voltage is taken
from the DAC VREF A pin.
VIN (0V TO +2.5V)
VREF A
VOUT
–50
20k
50k 100k 200k
500k
1M
INPUT FREQUENCY – Hz
Figure 6. Channel-to-Channel Isolation
AD644
PIN 8 OF TO-5 CAN (AD644)
V+
V–
AGND
AD7528 PIN 1
C1 LOCATION
VREF B*
VDD
WR
CS
LSB
AD7528
C2 LOCATION
VREF A*
DGND
DAC A/DAC B
MSB
*NOTE
INPUT SCREENS
TO REDUCE
FEEDTHROUGH.
LAYOUT SHOWS
COPPER SIDE
(i.e., BOTTOM VIEW).
Figure 7. Suggested PC Board Layout for AD7528 with
AD644 Dual Op Amp
VDD
+15V
DAC A
AD7528
OUT A
Figure 9. AD7528 in Single Supply, Voltage Switching Mode
3
TA = +25؇C
VDD = +15V
2
NONLINEARITY
1
DIFFERENTIAL
NONLINEARITY
2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5
VINA – Volts
Figure 10. Typical AD7528 Performance in Single Supply
Voltage Switching Mode (K/B/T, L/C/U Grades)
–6– REV. B

6 Page







SeitenGesamt 8 Seiten
PDF Download[ AD7528 Schematic.PDF ]

Link teilen




Besondere Datenblatt

TeilenummerBeschreibungHersteller
AD7520Multiplying D/A ConvertersHarris
Harris
AD752010-Bit/ 12-Bit/ Multiplying D/A ConvertersIntersil Corporation
Intersil Corporation
AD7520(AD7520 / AD7521) Monolithic Multiplying D/A ConvertersAnalog Devices
Analog Devices
AD7521Multiplying D/A ConvertersHarris
Harris
AD752110-Bit/ 12-Bit/ Multiplying D/A ConvertersIntersil Corporation
Intersil Corporation

TeilenummerBeschreibungHersteller
CD40175BC

Hex D-Type Flip-Flop / Quad D-Type Flip-Flop.

Fairchild Semiconductor
Fairchild Semiconductor
KTD1146

EPITAXIAL PLANAR NPN TRANSISTOR.

KEC
KEC


www.Datenblatt-PDF.com       |      2020       |      Kontakt     |      Suche