Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsData collecting ICsData acquisition IC - AD converter (ADC) Internal SOIC 24

_______________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

____________________________Features

♦ Low Supply Current:

60µA (Normal Operation)

1µA (Sleep-Mode Operation)

♦ ±0.006% FSR Accuracy at 16 Conv/sec

♦ Low Noise: 15µV

RMS

♦ Serial I/O Interface with Programmed Output for

Mux and PGA

♦ Performs up to 100 Conv/sec

♦ ±2pA Input Current

♦ 50Hz/60Hz Rejection

MAX132

±18-Bit ADC with Serial Interface

________________________________________________________________

Maxim Integrated Products

V+

BUF OUT

INT OUT

INT IN

SCLK

DOUT

DIN

TOP VIEW

CREF-

CREF+

REF+

REF-

OSC1

OSC2

AGND

IN LO

IN HI

V-

DGND

EOC

DIP/SO

MAX132

__________________Pin Configuration

MAX132

CREF- CREF+

602k

SCLK

DOUT

DIN

EOC

-5V

±512mV INPUT

BUF OUT

INT OUT

INT IN

4.7nF

REF+

REF-

AGND

IN LO

IN HI

V-

V+

DGND

OSC2OSC1

+5V

________________Functional Diagram

Call toll free 1-800-998-8800 for free samples or literature.

19-0009; Rev 2; 8/95

PART

MAX132CNG

MAX132CWG

MAX132C/D 0°C to +70°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

24 Narrow Plastic DIP

24 Wide SO

Dice*

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

______________Ordering Information

* Contact factory for dice specifications.

** Contact factory for availability and processing to MIL-STD-883.

MAX132ENG

MAX132EWG

MAX132MRG -55°C to +125°C

-40°C to +85°C

-40°C to +85°C 24 Narrow Plastic DIP

24 Wide SO

24 Narrow CERDIP**

Summary of content (16 pages)

PAGE 1
9-0009; Rev 2; 8/95 NUAL KIT MA ATION U EET L H A S V A E S DAT W O L L FO ±18-Bit ADC with Serial Interface The MAX132 is a CMOS, 18-bit plus sign, serial-output, analog-to-digital converter (ADC). Multi-slope integration 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).
PAGE 2
MAX132 ±18-Bit ADC with Serial Interface ABSOLUTE MAXIMUM RATINGS Supply Voltage V+ to DGND ..............................................-0.3V < V+ < +6.0V V- to DGND ................................................+0.3V < V- < -9.0V V+ to V- ............................................................................+15V Analog Input Voltage (any input).....................................V+ to VDigital Input Voltage .....................(DGND - 0.3V) to (V+ + 0.
PAGE 3
±18-Bit ADC with Serial Interface (V+ = 5V, V- = -5V, DGND = AGND = IN LO = REF- = 0V, REF+ = 545mV, R INT = 602kΩ, CINT = 0.0047µF, CREF = 0.1µF, fCLK = 32,768Hz, 60Hz mode, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP DOUT, IOUT = -1mA 3.5 4.3 DOUT, IOUT = -100µA 4.0 4.5 EOC, P0–P3, IOUT = -100µA 4.0 MAX UNITS DIGITAL SECTION Output High VOH V 4.7 DOUT, IOUT = 1.6mA 0.1 0.4 EOC, P0–P3, IOUT = 100µA 0.1 0.
PAGE 4
__________________________________________Typical Operating Characteristics -0.10 -0.15 -0.20 -0.25 3.0 2.5 2.0 1.5 1.0 60Hz MODE 0.5 1.4 60Hz MODE, VREF = 545mV 1.2 1.0 0.8 0.6 0.4 -4 -3 -2 -1 0 1 2 3 COMMON-MODE VOLTAGE (V) 4 0 0 SUPPLY CURRENT vs. CRYSTAL FREQUENCY 60 40 20 0 -20 -40 2.0 -20 0 20 40 60 80 VREF (V) TEMPERATURE (°C) FULL-SCALE ROLLOVER ERROR vs. VREF NOISE vs. NUMBER OF SAMPLES AVERAGED 100 20 0.08 15 NOISE (µVRMS) 80 1.5 1.
PAGE 5
±18-Bit ADC with Serial Interface PIN NAME 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 12 DGND 13 V- FUNCTION End of Conversion Output goes high at end of conversion.
PAGE 6
MAX132 ±18-Bit ADC with Serial Interface ____________Functional Description __________Analog Design Procedure The MAX132 integrates the input voltage for a fixed period of time, then deintegrates a known reference voltage and measures the time required to reach zero. Good line rejection is achieved by setting the (input) integration time equal to one 50Hz or 60Hz period.
PAGE 7
±18-Bit ADC with Serial Interface Reference Voltage Selection The reference voltage sets the analog input voltage range. For the nominal ±512mV full-scale input range, a 545mV reference voltage is used for the 60Hz mode and a 655mV reference voltage is used in the 50Hz mode. The reference voltage can be calculated as follows: CREF+ CREF REF+ REF- DE 60Hz Mode : VREF = or 50Hz Mode : VREF = (655 counts) (512) VIN(FS) ) 262,144 The recommended reference voltage range is 500mV to 700mV.
PAGE 8
MAX132 ±18-Bit ADC with Serial Interface Differential Reference Inputs and Rollover Error The main source of rollover voltage error is due to common-mode voltages. This error is caused by the reference capacitor losing or gaining charge to stray capacitance. A positive signal with a large commonmode voltage can cause the reference capacitor to gain charge (increase voltage). In contrast, the reference capacitor will lose charge (decrease voltage) when deintegrating a negative input signal.
PAGE 9
±18-Bit ADC with Serial Interface Conv/sec Crystal Freq. (Hz) CINT/60Hz (pF) CINT/50Hz (pF) Resistor (kΩ) 16 32,768 4700 6800 602 32 48 64 65,536 98, 304 131,072 2700 1800 1200 3300 2000 1500 602 602 602 80 96 163,840 196,608 1000 820 1200 1000 602 602 Note: Capacitor values are for a 3.0V integrator swing.
PAGE 10
MAX132 ±18-Bit ADC with Serial Interface ___________________Digital Interface Serial data at DIN is sent in 8-bit packets and is shifted into the internal 8-bit shift register with each rising edge of SCLK. The data is then latched into either command input register 0 or command input register 1, as determined by the LSB of the data sent, and is latched on the rising edge of CHIP SELECT (CS) Data is clocked out of the selected output register on each falling edge of SCLK.
PAGE 11
±18-Bit ADC with Serial Interface 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 typically 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.
PAGE 12
MAX132 ±18-Bit ADC with Serial Interface Command Input Register 1 Table 4. Overrange Values for Resolution Used Bits Used Resolution Bits Soft Overrange Start Value Hard Overrange Maximum Value B18–B3 ±15 34,880 43,805 B18–B2 ±16 69,760 87,610 B18–B1 ±17 139,520 175,220 B18–B0 ±18 279,040 350,440 Table 5.
PAGE 13
±18-Bit ADC with Serial Interface Sequence Counter and Results Counter A binary sequencing counter controls the conversion phase’s sequencing (or timing). In integrate phase, both start and stop occur at preset counts. The deintegration phases start at predetermined counts, but are terminated when the comparator detects zero crossing at the integrator output. The results counter accumulates counts during all deintegrate phases.
PAGE 14
MAX132 ±18-Bit ADC with Serial Interface Second Deintegrate Phase The second deintegrate phase deintegrates residual voltage on the integration capacitor that has been through the X8 phase. Since the voltage across the integration capacitor has been multiplied by 8, each deintegration clock cycle corresponds to 1/8 of one clock cycle during the first deintegration.
PAGE 15
±18-Bit ADC with Serial Interface Interfacing to a µP Parallel Port Figure 12 shows a high-level software subroutine for reading output/status data and writing command data to the MAX132. It provides an algorithm for serial communication when the µP port does not have a predefined serial interface protocol (i.e., SPI™ or Microwire™). The routine sends command data (TxByte) to the MAX132 while concurrently collecting the MAX132’s output register data (selected by the previous write cycle).
PAGE 16
±18-Bit ADC with Serial Interface MAX132 ___________________Chip Topography WAIT UNTIL EOC PIN IS HIGH CLEAR SCLK CLEAR CS BUF OUT INT OUT CS DOUT SCLK DIN V+ INT IN WRITE DIN132 FROM TxByte’s MSB OSC2 SET SCLK CREFCREF+ READ DOUT132 INTO RxByte’s LSB 0.186" (4.72mm) OSC1 PG0 CLEAR SCLK REF+ REF- SHIFT RxByte LEFT SHIFT TxByte LEFT PG1 REPEAT 8 TIMES PG2 SET CS RETURN RxByte Figure 12. MAX132 Read/Write Algorithm 16 EOC PG3 DGND 0.144" (3.