AD7845 Analog Devices, AD7845 Datasheet

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AD7845

Manufacturer Part Number
AD7845
Description
Complete 12-Bit CMOS Multiplying DAC
Manufacturer
Analog Devices
Datasheet

Specifications of AD7845

Resolution (bits)
12bit
Dac Update Rate
200kSPS
Dac Settling Time
5µs
Max Pos Supply (v)
+15.75V
Single-supply
No
Dac Type
Voltage Out
Dac Input Format
Par

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a
GENERAL DESCRIPTION
The AD7845 is the industry’s first 4-quadrant multiplying D/A
converter with an on-chip amplifier. It is fabricated on the
LC
and digital circuitry to be implemented on the same chip.
The 12 data inputs drive latches which are controlled by stan-
dard CS and WR signals, making microprocessor interfacing
simple. For stand-alone operation, the CS and WR inputs can
be tied to ground, making all latches transparent. All digital
inputs are TTL and 5 V CMOS compatible.
The output amplifier can supply 10 V into a 2 k load. It is
internally compensated, and its input offset voltage is low due to
laser trimming at wafer level. For normal operation, R
to V
scale the output voltage range.
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.
FEATURES
12-Bit CMOS MDAC with Output Amplifier
4-Quadrant Multiplication
Guaranteed Monotonic (T
Space-Saving 0.3" DIPs and 24- or 28-Terminal Surface
Application Resistors On Chip for Gain Ranging, etc.
Low Power LC
APPLICATIONS
Automatic Test Equipment
Digital Attenuators
Programmable Power Supplies
Programmable Gain Amplifiers
Digital-to-4–20 mA Converters
2
MOS process, which allows precision linear components
OUT
Mount Packages
, but the user may alternatively choose R
2
MOS
MIN
to T
MAX
)
A
, R
B
FB
or R
is tied
C
to
Complete 12-Bit Multiplying DAC
PRODUCT HIGHLIGHTS
1. Voltage Output Multiplying DAC
2. Matched Application Resistors
3. Space Saving
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
The AD7845 is the first DAC which has a full 4-quadrant
multiplying capability and an output amplifier on chip. All
specifications include amplifier performance.
Three application resistors provide an easy facility for gain
ranging, voltage offsetting, etc.
The AD7845 saves space in two ways. The integration of the
output amplifier on chip means that chip count is reduced.
The part is housed in skinny 24-lead 0.3" DIP, 28-terminal
LCC and PLCC and 24-terminal SOIC packages.
FUNCTIONAL BLOCK DIAGRAM
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 1999
AD7845
LC
2
MOS

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AD7845 Summary of contents

Page 1

... Matched Application Resistors Three application resistors provide an easy facility for gain ranging, voltage offsetting, etc. 3. Space Saving The AD7845 saves space in two ways. The integration of the output amplifier on chip means that chip count is reduced. The part is housed in skinny 24-lead 0.3" DIP, 28-terminal is tied LCC and PLCC and 24-terminal SOIC packages ...

Page 2

... AD7845–SPECIFICATIONS V connected load = 100 pF. All specifications T OUT FB OUT Parameter J Version K Version ACCURACY Resolution 12 12 Relative Accuracy 3/4 MIN MAX Differential Nonlinearity 1 1 Zero Code Offset Error at + MIN MAX Offset Temperature Coefficient; ...

Page 3

... 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 AD7845 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 ...

Page 4

... DIP, SOIC TERMINOLOGY LEAST SIGNIFICANT BIT This is the analog weighting of 1 bit of the digital word REF DAC. For the AD7845, 1 LSB = 12 2 RELATIVE ACCURACY 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 measured after adjusting for both endpoints (i ...

Page 5

... Figure 8. Unity Gain Inverter Pulse Response (Large Signal) REV. B Typical Performance Characteristics–AD7845 Figure 3. Output Voltage Swing vs. Resistive Load Figure 6. Typical AD7845 Linearity vs. Power Supply Figure 9. Unity Gain Inverter Pulse Response (Small Signal) –5– Figure 4. Noise Spectral Density Figure 7. Multiplying Feedthrough Error vs ...

Page 6

... FB CIRCUIT INFORMATION Digital Section Figure simplified circuit diagram of the AD7845 input control logic. When CS and WR are both low, the DAC latch is loaded with the data on the data inputs. All the digital inputs are TTL, HCMOS and +5 V CMOS compatible, facilitating easy microprocessor interfacing ...

Page 7

... UNIPOLAR BINARY OPERATION Figure 13 shows the AD7845 connected for unipolar binary operation. When signal, the circuit performs IN 2-quadrant multiplication. The code table for Figure 13 is given in Table I. Figure 13. Unipolar Binary Operation Table I. Unipolar Binary Code Table for AD7845 Binary Number In ...

Page 8

... AD7845 CATION APPLI S CIRCUITS PROGRAMMABLE GAIN AMPLIFIER (PGA) The AD7845 performs a PGA function when connected as in Figure 15. In this configuration, the R-2R ladder is connected in the amplifier feedback loop the amplifier input resis- FB tor. As the code decreases, the R-2R ladder resistance increases and so the gain increases. ...

Page 9

... AD7845 V ground. Temperature Coefficients: The gain temperature coefficient of the AD7845 has a maximum value of 5 ppm/ C. This corre- sponds to worst case gain shift of 2 LSBs over a 100 C tem- perature range. When trim resistors R1 and R2 in Figure 13 are used to adjust full-scale range, the temperature coefficient of R1 and R2 must be taken into account ...

Page 10

... Figure 20. AD7845 to 8086 Interface Figure 21. TMS32010 8-BIT MICROPROCESSOR SYSTEMS Figure 22 shows an interface circuit for the AD7845 to the 8085A 8-bit microprocessor. The software routine to load data to the device is given in Table IV. Note that the transfer of the 12 bits of data requires two write operations. The first of these loads the 4 MSBs into the 7475 latch ...

Page 11

... REV. B DIGITAL FEEDTHROUGH In the preceding interface configurations, most digital inputs to the AD7845 are directly connected to the microprocessor bus. Even when the device is not selected, these inputs will be con- stantly changing. The high frequency logic activity on the bus can feed through the DAC package capacitance to show up as noise on the analog output ...

Page 12

... AD7845 24-Lead Plastic DIP (N-24) 24-Lead Cerdip (Q-24) 24-Lead Ceramic DIP (D-24A) OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 28-Terminal Leadless Ceramic Chip Carrier 28-Terminal Plastic Leaded Chip Carrier 0.6141 (15.60) 0.5985 (15.20 PIN 1 0.0500 0.0118 (0.30) 0.0192 (0.49) (1.27) 0.0138 (0.35) 0.0040 (0.10) BSC –12– (E-28A) (P-28A) 24-Lead SOIC ...

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