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PDF ( 数据手册 , 数据表 ) DAC8408FPC

零件编号 DAC8408FPC
描述 Quad 8-Bit Multiplying CMOS D/A Converter with Memory
制造商 Analog Devices
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DAC8408FPC 数据手册, 描述, 功能
a
Quad 8-Bit Multiplying CMOS
D/A Converter with Memory
DAC8408
FEATURES
Four DACs in a 28 Pin, 0.6 Inch Wide DIP or 28-Pin JEDEC
Plastic Chip Carrier
؎1/4 LSB Endpoint Linearity
Guaranteed Monotonic
DACs Matched to Within 1%
Microprocessor Compatible
Read/Write Capability (with Memory)
TTL/CMOS Compatible
Four-Quadrant Multiplication
Single-Supply Operation (+5 V)
Low Power Consumption
Latch-Up Resistant
Available In Die Form
APPLICATIONS
Voltage Set Points in Automatic Test Equipment
Systems Requiring Data Access for Self-Diagnostics
Industrial Automation
Multichannel Microprocessor-Controlled Systems
Digitally Controlled Op Amp Offset Adjustment
Process Control
Digital Attenuators
GENERAL DESCRIPTION
The DAC8408 is a monolithic quad 8-bit multiplying digital-to-
analog CMOS converter. Each DAC has its own reference input,
feedback resistor, and onboard data latches that feature
read/write capability. The readback function serves as memory
for those systems requiring self-diagnostics.
A common 8-bit TTL/CMOS compatible input port is used to
load data into any of the four DAC data-latches. Control lines
DS1, DS2, and A/B determine which DAC will accept data.
Data loading is similar to that of a RAMs write cycle. Data can
be read back onto the same data bus with control line R/W. The
DAC8408 is bus compatible with most 8-bit microprocessors,
including the 6800, 8080, 8085, and Z80. The DAC8408 oper-
ates on a single +5 volt supply and dissipates less than 20 mW.
The DAC8408 is manufactured using PMI’s highly stable,
thin-film resistors on an advanced oxide-isolated, silicon-gate,
CMOS process. PMI’s improved latch-up resistant design elimi-
nates the need for external protective Schottky diodes.
ORDERING INFORMATION1
Model
Temperature Package
INL DNL Range
Description
DAC8408GP ± 1/4 LSB ± 1/2 LSB 0°C to +70°C
DAC8408ET ± 1/4 LSB ± 1/2 LSB –40°C to +85°C
DAC8408AT2 ± 1/4 LSB ± 1/2 LSB –55°C to +125°C
DAC8408FT ± 1/2 LSB ± 1 LSB –40°C to +85°C
DAC8408BT2 ± 1/2 LSB ± 1 LSB –55°C to +125°C
DAC8408FPC3 ± 1/2 LSB ± 1 LSB –40°C to +85°C
DAC8408FS ± 1/2 LSB ± 1 LSB –40°C to +85°C
DAC8408FP ± 1/2 LSB ± 1 LSB –40°C to +85°C
28-Pin Plastic DIP
28-Pin Cerdip
28-Pin Cerdip
28-Pin Cerdip
28-Pin Cerdip
28-Contact PLCC
28-Pin SOL
28-Pin Plastic DIP
NOTES
1Burn-in is available on commercial and industrial temperature range parts
in cerdip, plastic DIP, and TO-can packages. For outline information see Pack-
age Information section.
2For devices processed in total compliance to MIL-STD-883, add /883 after
part number. Consult factory for 883 data sheet.
3For availability and burn-in information on SO and PLCC packages, contact
your local sales office.
FUNCTIONAL BLOCK DIAGRAM
DAC8408
REV. A
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
Fax: 617/326-8703







DAC8408FPC pdf, 数据表
DAC8408
CIRCUIT INFORMATION
The DAC8408 combines four identical 8-bit CMOS DACs
onto a single monolithic chip. Each DAC has its own reference
input, feedback resistor, and on-board data latches. It also fea-
tures a read/write function that serves as an accessible memory
location for digital-input data words. The DAC’s three-state
readback drivers place the data word back onto the data bus.
D/A CONVERTER SECTION
Each DAC contains a highly stable, silicon-chromium, thin-film,
R-2R resistor ladder network and eight pairs of current steering
switches. These switches are in series with each ladder resistor
and are single-pole, double-throw NMOS transistors; the gates
of these transistors are controlled by CMOS inverters. Figure 1
shows a simplified circuit of the R-2R resistor ladder section,
and Figure 2 shows an approximate equivalent switch circuit.
The current through each resistor leg is switched between IOUT 1
and IOUT 2. This maintains a constant current in each leg, re-
gardless of the digital input logic states.
Each transistor switch has a finite “ON” resistance that can in-
troduce errors to the DAC’s specified performance. These resis-
tances must be accounted for by making the voltage drop across
each transistor equal to each other. This is done by binarily-
scaling the transistor’s “ON” resistance from the most signifi-
cant bit (MSB) to the least significant bit (LSB). With 10 volts
applied at the reference input, the current through the MSB
switch is 0.5 mA, the next bit is 0.25 mA, etc.; this maintains a
constant 10 mV drop across each switch and the converter’s ac-
curacy is maintained. It also results in a constant resistance ap-
pearing at the DAC’s reference input terminal; this allows the
DAC to be driven by a voltage or current source, ac or dc of
positive or negative polarity.
Shown in Figure 3 is an equivalent output circuit for DAC A.
The circuit is shown with all digital inputs high. The leakage
current source is the combination of surface and junction leak-
ages to the substrate. The 1/256 current source represents the
constant 1-bit current drain through the ladder terminating re-
sistor. The situation is reversed with all digital inputs low, as
shown in Figure 4. The output capacitance is code dependent,
and therefore, is modulated between the low and high values.
Figure 1. Simplified D/A Circuit of DAC8408
Figure 2. N-Channel Current Steering Switch
Figure 3. Equivalent DAC Circuit (AII Digital Inputs HIGH)
–8– REV. A







DAC8408FPC equivalent, schematic
–16–










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