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PDF MAX132 Data sheet ( Hoja de datos )
| Número de pieza | MAX132 | |
| Descripción | 18-Bit ADC with Serial Interface | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-0009; Rev 2; 8/95
EVFAOLLULAOTWIOSNDKAITTAMSAHNEUEATL
±18-Bit ADC with Serial Interface
_______________General Description
The MAX132 is a CMOS, 18-bit plus sign, serial-output,
analog-to-digital converter (ADC). Multi-slope integra-
tion provides high-resolution conversions in less time
than standard integrating ADCs, allowing operation up
to 100 conversions per second. Low conversion noise
provides guaranteed operation with ±512mV full-scale
input range (2µV/LSB). A simple 4-wire serial interface
connects easily to all common microprocessors, and
twos-complement output coding simplifies bipolar mea-
surements. Typical supply current is only 60µA and is
reduced to 1µA in sleep mode. Four serially pro-
grammed digital outputs can be used to control an
external multiplexer or programmable-gain amplifier.
The MAX132 comes in 24-pin narrow DIP and wide SO
packages, and is available in commercial and extend-
ed temperature grades.
High resolution, compact size, and low power make this
device ideal for data loggers, weigh scales, data-acqui-
sition systems, and panel meters.
________________________Applications
Remote Data Acquisition
Battery-Powered Instruments
Industrial Process Control
Transducer-Signal Measurement
Pressure, Flow, Temperature, Voltage
Current, Resistance, Weight
________________Functional Diagram
____________________________Features
o Low Supply Current:
60µA (Normal Operation)
1µA (Sleep-Mode Operation)
o ±0.006% FSR Accuracy at 16 Conv/sec
o Low Noise: 15µVRMS
o Serial I/O Interface with Programmed Output for
Mux and PGA
o Performs up to 100 Conv/sec
o ±2pA Input Current
o 50Hz/60Hz Rejection
______________Ordering Information
PART
TEMP. RANGE PIN-PACKAGE
MAX132CNG
0°C to +70°C 24 Narrow Plastic DIP
MAX132CWG
0°C to +70°C 24 Wide SO
MAX132C/D
0°C to +70°C Dice*
MAX132ENG -40°C to +85°C 24 Narrow Plastic DIP
MAX132EWG -40°C to +85°C 24 Wide SO
MAX132MRG -55°C to +125°C 24 Narrow CERDIP**
* Contact factory for dice specifications.
** Contact factory for availability and processing to MIL-STD-883.
__________________Pin Configuration
CREF-
CREF+
V+
CS
SCLK
EOC
DIN
DOUT
BUF OUT
INT OUT
INT IN
REF+
REF-
AGND
MAX132
P0 IN LO
P1 IN HI
P2 V-
P3
OSC1
DGND
OSC2
+5V
602k
4.7nF
±512mV INPUT
-5V
TOP VIEW
CS 1
DIN 2
DOUT 3
SCLK 4
OSC2 5
OSC1 6
P0 7
P1 8
P2 9
P3 10
EOC 11
DGND 12
MAX132
DIP/SO
24 V+
23 BUF OUT
22 INT OUT
21 INT IN
20 CREF-
19 CREF+
18 REF+
17 REF-
16 AGND
15 IN LO
14 IN HI
13 V-
________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
1 page  
±18-Bit ADC with Serial Interface
_________________________________________________Pin Description (continued)
PIN NAME
FUNCTION
9 P2 User-programmable output bit 2—programmed through the serial port.
10 P3 User-programmable output bit 3—programmed through the serial port.
11
EOC
End of Conversion Output goes high at end of conversion.
12 DGND Digital Ground—power-supply return
13 V- Negative Supply, nominally -5V
14
IN HI
Positive Analog Input
15 IN LO Negative Analog Input
16 AGND Analog Ground
17
REF-
Negative Reference Input
18
REF+
Positive Reference Input
19 CREF+ Positive Reference Capacitor connection
20 CREF- Negative Reference Capacitor connection
21 INT IN Integrator Input. Connect the integration capacitor between INT IN and INT OUT.
22 INT OUT Integrator Output. To minimize noise, this pin should drive the capacitor’s outside foil (negative end).
23 BUF OUT Buffer-Amplifier Output drives the integrator resistor.
24 V+ Positive Supply, nominally +5V
0.1µF
20
CREF-
1 CS
4 SCLK
11 EOC
2 DIN
3 DOUT
7 P0
8 P1
9 P2
10 P3
MAX132
OSC1
6
32,768Hz
15pF
+5V
19
CREF+
V+
24
BUF OUT 23 602k
INT OUT 22
21 4.7nF
INT IN
REF+
REF-
AGND
IN LO
IN HI
V-
DGND
18
17
16
15
14
13
12
-5V
OSC2
5
15pF
2.5V
120k
100k
40.2k
512mV INPUT
MAX872
Figure 1. Test and Typical Application Circuit
_______________________________________________________________________________________ 5
5 Page 
±18-Bit ADC with Serial Interface
Averaging 2 or 3 read-zero measurements provides the
most accurate read-zero value. Perform a read-zero
sequence whenever a large change in the input voltage
is expected.
Sleep Bit
When the sleep bit is set to 1, (bit D5 in command input
register 0), the low-power sleep mode starts when EOC
returns high. In sleep mode, the supply current is typi-
cally 1µA and the oscillator shuts down. The interface
remains active and data can be read. When exiting
sleep mode, the analog circuitry needs time to stabilize
before the next conversion starts. Accomplish this by
writing a dummy instruction to emerge from sleep
mode, and wait at least one conversion cycle before
writing a start instruction.
50Hz/60Hz
With a 32,768Hz crystal, the 50Hz/60Hz bit sets the
integrate period equal to one line cycle for 50Hz/60Hz
environments. When D6 (in command input register 0)
is set to 0, the integrate count is an integer multiple of
60Hz (32,768Hz/60Hz = 546 counts). When D6 is set to
1, the integrate input count is an integer multiple of
50Hz (32,768Hz/50Hz = 655 counts). Achieve the
greatest AC rejection by adjusting the integration peri-
od for 50Hz or 60Hz.
Start Conversion Bit
The start conversion bit (D7) in command input register
0 initiates a conversion when set to 1. The MAX132
immediately starts a conversion, stops at conversion
end, and then waits for the next start-bit command. A
start instruction is needed to initiate each conversion.
To initiate a continuous data stream, write a separate
start command for each conversion in three ways:
1) Wait longer than a known conversion time and then
write another start command.
2) Poll either the EOC status register bit or the EOC
line to determine conversion end and start time for
the next conversion. EOC becomes 1 at conversion
end at count 0000 of the conversion counter (Figure
10).
3) Set the start bit to 1 before a conversion end. The
internal conversion counter is then checked for its
count. If the count is 0000 (EOC = 1), a new conver-
sion starts and the conversion counter is set to
0001. The start bit resets to 0 after 5 clock cycles.
The MAX132 will not check the start bit again until
the conversion counter returns to a 0000 count. This
means a start command can be given any time after
0005 internal conversion count; the next conversion
starts when the counter returns to 0000.
RESET
0000
0001
60Hz
INT START
0111
ZERO INT
INTEGRATE
50Hz mode
655
545
60Hz mode
CHOP
659 667
INT OUT
INTERNAL CONVERSION DATA LATCH
1346 1600
1638
1783
RESET EVENTS
1823 1970 2017
2047 0000
DE-1
679
MAX
545
MAX
SOFT
OVERRANGE
AREA
(SEE TEXT)
X8-1
264
DE-2 X8-2 DE-3 X8-3 DE-4 ZERO INT
38 145 40 147 47 30
LATCH
EOC
Figure 10. Conversion Timing (Negative Input Shown)
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MAX132.PDF ] | |
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