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ManualsBrandsANALOG DEVICES ManualsData collecting ICsData acquisition IC - DA converter (DAC) PDIP 24

REV. B

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MOS

Complete 12-Bit Multiplying DAC

AD7845

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., 1999

FUNCTIONAL BLOCK DIAGRAM

PRODUCT HIGHLIGHTS

1. Voltage Output Multiplying DAC

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.

2. 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

LCC and PLCC and 24-terminal SOIC packages.

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

MOS process, which allows precision linear components

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 kΩ load. It is

internally compensated, and its input offset voltage is low due to

laser trimming at wafer level. For normal operation, R

is tied

to V

OUT

, but the user may alternatively choose R

, R

or R

scale the output voltage range.

FEATURES

12-Bit CMOS MDAC with Output Amplifier

4-Quadrant Multiplication

Guaranteed Monotonic (T

MIN

to T

MAX

)

Space-Saving 0.3" DIPs and 24- or 28-Terminal Surface

Mount Packages

Application Resistors On Chip for Gain Ranging, etc.

Low Power LC

MOS

APPLICATIONS

Automatic Test Equipment

Digital Attenuators

Programmable Power Supplies

Programmable Gain Amplifiers

Digital-to-4–20 mA Converters

Summary of content (12 pages)

PAGE 1
a FEATURES 12-Bit CMOS MDAC with Output Amplifier 4-Quadrant Multiplication Guaranteed Monotonic (TMIN to T MAX) Space-Saving 0.3" DIPs and 24- or 28-Terminal Surface Mount Packages Application Resistors On Chip for Gain Ranging, etc.
PAGE 2
1 (V = +15 V, ⴞ 5%, V = –15 V, ⴞ 5%, V AD7845–SPECIFICATIONS V connected to R . V load = 2 k⍀, 100 pF. All specifications T to T unless otherwise noted.
PAGE 3
AD7845 TIMING CHARACTERISTICS1 (V DD = +15 V, ⴞ 5%. VSS = –15 V, ⴞ 5%. VREF = +10 V. AGND = DGND = O V.) Parameter Limit at TMIN to TMAX (All Versions) Units Test Conditions/Comments tCS tCH tWR tDS tDH 30 0 30 80 0 ns min ns min ns min ns min ns min Chip Select to Write Setup Time Chip Select to Write Hold Time Write Pulsewidth Data Setup Time Data Hold Time NOTES 1 Guaranteed by design and characterization, not production tested. Specifications subject to change without notice.
PAGE 4
AD7845 PIN CONFIGURATIONS DIP, SOIC LCC PLCC TERMINOLOGY LEAST SIGNIFICANT BIT DIGITAL-TO-ANALOG GLITCH IMPULSE This is the analog weighting of 1 bit of the digital word in a V REF DAC. For the AD7845, 1 LSB = 12 . 2 This is the amount of charge injected from the digital inputs to the analog output when the inputs change state. This is normally specified as the area of the glitch in either pA-secs or nV-secs depending upon whether the glitch is measured as a current or voltage.
PAGE 5
Typical Performance Characteristics–AD7845 Figure 2. Frequency Response, G = –1 Figure 3. Output Voltage Swing vs. Resistive Load Figure 5. THD vs. Frequency Figure 6. Typical AD7845 Linearity vs. Power Supply Figure 4. Noise Spectral Density Figure 7. Multiplying Feedthrough Error vs. Frequency 80 70 60 OUTPUT – mV 50 40 30 20 10 0 –10 –20 Figure 8. Unity Gain Inverter Pulse Response (Large Signal) REV. B Figure 9.
PAGE 6
AD7845 PIN FUNCTION DESCRIPTION (DIP) Pin Mnemonic Description 1 2-11 12 13-14 15 16 17 18 19 20 21 22 23 24 VOUT DB11–DB2 DGND DB1–DB0 WR CS VREF AGND VSS VDD RA RB RC RFB Voltage Output Terminal Data Bit 11 (MSB) to Data Bit 2 Digital Ground. The metal lid on the ceramic package is connected to this pin Data Bit 1 to Data Bit 0 (LSB) Write Input. Active low Chip Select Input. Active low Reference Input Voltage which can be an ac or dc signal Analog Ground.
PAGE 7
AD7845 UNIPOLAR BINARY OPERATION Figure 13 shows the AD7845 connected for unipolar binary operation. When VIN is an ac signal, the circuit performs 2-quadrant multiplication. The code table for Figure 13 is given in Table I. BIPOLAR OPERATION (4-QUADRANT MULTIPLICATION) The recommended circuit for bipolar operation is shown in Figure 14. Offset binary coding is used.
PAGE 8
AD7845 APPLICATION S CIRCUITS PROGRAMMABLE GAIN AMPLIFIER (PGA) PROGRAMMABLE CURRENT SOURCES The AD7845 is ideal for designing programmable current sources using a minimum of external components. Figures 16 and 17 are examples. The circuit of Figure 16 drives a programmable current IL into a load referenced to a negative supply. Figure 17 shows the circuit for sinking a programmable current, IL. The same set of circuit equations apply for both diagrams.
PAGE 9
AD7845 Figure 18. 4–20 mA Current Loop Figure 17. Programmable Current Sink 4–20 mA CURRENT LOOP APPLICATION HINTS The AD7845 provides an excellent way of making a 4-20 mA current loop circuit. This is basically a variation of the circuits in Figures 16 and 17 and is shown in Figure 18. The application resistor RA (Value 4R) produces the effective 4 mA offset. General Ground Management: AC or transient voltages between AGND and DGND can cause noise injection into the analog output.
PAGE 10
AD7845 MICROPROCESSOR INTERFACING 16-BIT MICROPROCESSOR SYSTEMS Figures 19, 20 and 21 show how the AD7845 interfaces to three popular 16-bit microprocessor systems. These are the MC68000, 8086 and the TM32010. The AD7845 is treated as a memory-mapped peripheral to the processors. In each case, a write instruction loads the AD7845 with the appropriate data.
PAGE 11
AD7845 Figure 23 and 24 are the interface circuits for the Z80 and MC6809 microprocessors. Again, these use the same basic format as the 8085A interface. 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 constantly changing.
PAGE 12
AD7845 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 28-Terminal Leadless Ceramic Chip Carrier (E-28A) 24-Lead Cerdip (Q-24) 28-Terminal Plastic Leaded Chip Carrier (P-28A) 24-Lead Ceramic DIP (D-24A) 24-Lead SOIC (R-24) C1189b–1–9/99 24-Lead Plastic DIP (N-24) 0.6141 (15.60) 0.5985 (15.20) 24 13 1 PIN 1 0.0118 (0.30) 0.0500 0.0040 (0.10) (1.27) BSC –12– 12 0.4193 (10.65) 0.3937 (10.00) 0.1043 (2.65) 0.0926 (2.35) 88 08 0.0192 (0.49) SEATING 0.0125 (0.32) PLANE 0.0138 (0.35) 0.