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ADC08134CIWM Schematic ( PDF Datasheet ) - National Semiconductor

Teilenummer ADC08134CIWM
Beschreibung 8-Bit High-Speed Serial I/O A/D Converters with Multiplexer Options/ Voltage Reference/ and Track/Hold Function
Hersteller National Semiconductor
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ADC08134CIWM Datasheet, Funktion
June 1999
ADC08131/ADC08134/ADC08138
8-Bit High-Speed Serial I/O A/D Converters with
Multiplexer Options, Voltage Reference, and Track/Hold
Function
General Description
The ADC08131/ADC08134/ADC08138 are 8-bit successive
approximation A/D converters with serial I/O and config-
urable input multiplexers with up to 8 channels. The serial
I/O is configured to comply with the NSC MICROWIREse-
rial data exchange standard for easy interface to the
COPSfamily of controllers, and can easily interface with
standard shift registers or microprocessors.
All three devices provide a 2.5V band-gap derived reference
with guaranteed performance over temperature.
A track/hold function allows the analog voltage at the positive
input to vary during the actual A/D conversion.
The analog inputs can be configured to operate in various
combinations of single-ended, differential, or
pseudo-differential modes. In addition, input voltage spans
as small as 1V can be accommodated.
Applications
n Digitizing automotive sensors
n Process control/monitoring
n Remote sensing in noisy environments
n Embedded diagnostics
Features
n Serial digital data link requires few I/O pins
n Analog input track/hold function
n 4- or 8-channel input multiplexer options with address
logic
n On-chip 2.5V band-gap reference (±2% over
temperature guaranteed)
n No zero or full scale adjustment required
n TTL/CMOS input/output compatible
n 0V to 5V analog input range with single 5V power
supply
Key Specifications
n Resolution
8 Bits
n Conversion time (fC = 1 MHz)
8 µs (Max)
n Power dissipation
20 mW (Max)
n Single supply
n Total unadjusted error
5 VDC (±5%)
±12 LSB and ±1 LSB
n Linearity Error (VREF = 2.5V)
±12 LSB
n No missing codes (over temperature)
n On-board Reference
+2.5V ±1.5% (Max)
Ordering Information
Industrial
(−40˚C TA +85˚C)
ADC08131CIWM
ADC08134CIWM
ADC08138CIWM
Package
M14B
M14B
M20B
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
COPSmicrocontrollers and MICROWIREare trademarks of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation DS010749
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ADC08134CIWM Datasheet, Funktion
ADC08138 Simplified Block Diagram
DS010749-1
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ADC08134CIWM pdf, datenblatt
Functional Description
MULTIPLEXER ADDRESSING
The design of these converters utilizes a comparator struc-
ture with built-in sample-and-hold which provides for a differ-
ential analog input to be converted by a successiveapproxi-
mation routine.
The actual voltage converted is always the difference be-
tween an assigned “+” input terminal and a “−” input terminal.
The polarity of each input terminal of the pair indicates which
line the converter expects to be the most positive. If the as-
signed “+” input voltage is less than the “−” input voltage the
converter responds with an all zeros output code.
A unique input multiplexing scheme has been utilized to pro-
vide multiple analog channels with software-configurable
single-ended, differential, or pseudo-differential (which will
convert the difference between the voltage at any analog in-
put and a common terminal) operation. The analog signal
conditioning required in transducer-based data acquisition
systems is significantly simplified with this type of input flex-
ibility. One converter package can now handle ground refer-
enced inputs and true differential inputs as well as signals
with some arbitrary reference voltage.
A particular input configuration is assigned during the MUX
addressing sequence, prior to the start of a conversion. The
MUX address selects which of the analog inputs are to be
enabled and whether this input is single-ended or differential.
Differential inputs are restricted to adjacent channel pairs.
For example, channel 0 and channel 1 may be selected as a
differential pair but channel 0 or 1 cannot act differentially
with any other channel. In addition to selecting differential
mode the polarity may also be selected. Channel 0 may be
selected as the positive input and channel 1 as the negative
input or vice versa. This programmability is best illustrated by
the MUX addressing codes shown in the following tables for
the various product options.
The MUX address is shifted into the converter via the DI line.
Because the ADC08131 contains only one differential input
channel with a fixed polarity assignment, it does not require
addressing.
The common input line (COM) on the ADC08138 can be
used as a pseudo-differential input. In this mode the voltage
on this pin is treated as the “−” input for any of the other input
channels. This voltage does not have to be analog ground; it
can be any reference potential which is common to all of the
inputs. This feature is most useful in single-supply applica-
tions where the analog circuity may be biased up to a poten-
tial other than ground and the output signals are all referred
to this potential.
TABLE 1. Multiplexer/Package Options
Part
Number
ADC08131
ADC08134
ADC08138
Number of Analog Channels
Single-Ended Differential
11
42
84
Number of
Package
Pins
8
14
20
TABLE 2. MUX Addressing: ADC08138
Single-Ended MUX Mode
MUX Address
Analog Single-Ended Channel #
START
SGL/
ODD/
SELECT
01
23
45
6 7 COM
DIF
SIGN
1
0
1 1 0 00+
1 1 0 01
+
1 1 0 10
+−
1 1 0 11
+−
1 1 1 00
+
1 1 1 01
+
1 1 1 10
+−
1 1 1 11
+−
Differential MUX Mode
MUX Address
START
SGL/
ODD/
DIF SIGN
1 00
1 00
1 00
1 00
1 01
1 01
TABLE 3. MUX Addressing: ADC08138
SELECT
10
00
01
10
11
00
01
0
01
+−
−+
Analog Differential Channel-Pair #
12
2345
+−
+−
−+
3
67
+−
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