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_______________General Description

The MAX197 multi-range, 12-bit data-acquisition sys-

tem (DAS) requires only a single +5V supply for opera-

tion, yet accepts signals at its analog inputs that may

span both above the power-supply rail and below

ground. This system provides 8 analog input channels

that are independently software programmable for a

variety of ranges: ±10V, ±5V, 0V to +10V, or 0V to +5V.

This increases effective dynamic range to 14 bits, and

provides the user flexibility to interface 4mA-to-20mA,

±12V, and ±15V powered sensors to a single +5V sys-

tem. In addition, the converter is overvoltage tolerant to

±16.5V; a fault condition on any channel does not

affect the conversion result of the selected channel.

Other features include a 5MHz bandwidth track/hold, a

100ksps throughput rate, software-selectable internal or

external clock and acquisition, 8+4 parallel interface,

and an internal 4.096V or an external reference.

A hardware SHDN pin and two programmable power-

down modes (STBYPD, FULLPD) are provided for low-

current shutdown between conversions. In STBYPD

mode, the reference buffer remains active, eliminating

start-up delays.

The MAX197 employs a standard microprocessor (µP)

interface. A three-state data I/O port is configured to

operate with 8-bit data buses, and data-access and

bus-release timing specifications are compatible with

most popular µPs. All logic inputs and outputs are

TTL/CMOS compatible.

The MAX197 is available in 28-pin DIP, wide SO, SSOP,

and ceramic SB packages.

For a different combination of ranges (±4V, ±2V, 0V to

4V, 0V to 2V), refer to the MAX199 data sheet. For 12-bit

bus interface, refer to the MAX196 and MAX198 data

sheets.

________________________Applications

Industrial-Control Systems

Robotics

Data-Acquisition Systems

Automatic Testing Systems

Medical Instruments

Telecommunications

____________________________Features

♦ 12-Bit Resolution, 1/2LSB Linearity

♦ Single +5V Operation

♦ Software-Selectable Input Ranges:

±10V, ±5V, 0V to 10V, 0V to 5V

♦ Fault-Protected Input Multiplexer (±16.5V)

♦ 8 Analog Input Channels

♦ 6µs Conversion Time, 100ksps Sampling Rate

♦ Internal or External Acquisition Control

♦ Internal 4.096V or External Reference

♦ Two Power-Down Modes

♦ Internal or External Clock

MAX197

Multi-Range (±10V, ±5V, +10V, +5V),

Single +5V, 12-Bit DAS with 8+4 Bus Interface

________________________________________________________________ Maxim Integrated Products 1

DGND

REF

REFADJ

INT

CH7

AGND

CH6

CH5

CH4

CH3

CH2

CH1

CH0

D0/D8

D1/D9

D2/D10

D3/D11

SHDN

HBEN

CLK

DIP/SO/SSOP/Ceramic SB

TOP VIEW

MAX197

__________________Pin Configuration

19-0381; Rev 2; 9/01

PART

MAX197ACNI

MAX197BCNI

MAX197ACWI 0°C to +70°C

0°C to +70°C

TEMP RANGE PIN-PACKAGE

28 Narrow Plastic DIP

28 Wide SO

______________Ordering Information

MAX197BCWI 0°C to +70°C 28 Wide SO

MAX197ACAI 0°C to +70°C 28 SSOP

MAX197BCAI 0°C to +70°C 28 SSOP

MAX197BC/D 0°C to +70°C Dice*

Ordering Information continued at end of data sheet.

*Dice are specified at T

= +25°C, DC parameters only.

EVALUATION KIT

MANUAL AVAILABLE

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Functional Diagram appears at end of data sheet.

Summary of content (16 pages)

PAGE 1
9-0381; Rev 2; 9/01 KIT ATION EVALU ABLE IL A V LA MANUA Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface ________________________Applications Industrial-Control Systems Robotics Data-Acquisition Systems Automatic Testing Systems Medical Instruments Telecommunications Functional Diagram appears at end of data sheet.
PAGE 2
MAX197 Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface ABSOLUTE MAXIMUM RATINGS VDD to AGND............................................................-0.3V to +7V AGND to DGND.....................................................-0.3V to +0.3V REF to AGND..............................................-0.3V to (VDD + 0.3V) REFADJ to AGND.......................................-0.3V to (VDD + 0.3V) Digital Inputs to DGND...............................-0.3V to (VDD + 0.
PAGE 3
Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface (VDD = 5V ±5%; unipolar/bipolar range; external reference mode, VREF = 4.096V; 4.7µF at REF pin; external clock, fCLK = 2.0MHz with 50% duty cycle; TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 3 µs ANALOG INPUT Track/Hold Acquisition Time fCLK = 2.0MHz Small-Signal Bandwidth -3dB rolloff ±10V range 5 ±5V range 2.5 0V to 10V range 2.
PAGE 4
MAX197 Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface ELECTRICAL CHARACTERISTICS (continued) (VDD = 5V ±5%; unipolar/bipolar range; external reference mode, VREF = 4.096V; 4.7µF at REF pin; external clock, fCLK = 2.0MHz with 50% duty cycle; TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 5.25 V POWER REQUIREMENTS Supply Voltage VDD 4.
PAGE 5
Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface (VDD = 5V ±5%; unipolar/bipolar range; external reference mode, VREF = 4.096V; 4.7µF at REF pin; external clock, fCLK = 2.0MHz with 50% duty cycle; TA = TMIN to TMAX, unless otherwise noted.
PAGE 6
__________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) EFFECTIVE NUMBER OF BITS vs. INPUT FREQUENCY FFT PLOT -20 AMPLITUDE (dB) 0.150 0.100 0.050 0.000 -40 -60 -80 -0.050 FSAMPLE = 100kHz 11.5 11.0 10.5 -100 -120 1000 3000 2000 4000 10.0 0 25 DIGITAL CODE 50 MAX197-4 0.4 VDD = 5V ±0.25V 0.2 PSRR (LSB) VREF (V) 4.095 4.090 4.085 AV = 1.6384 +2.5V INTERNAL REFERENCE REFADJ 100Hz -0.2 0.
PAGE 7
Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface PIN NAME FUNCTION 1 CLK Clock Input. In external clock mode, drive CLK with a TTL/CMOS compatible clock. In internal clock mode, place a capacitor from this pin to ground to set the internal clock frequency; fCLK = 1.56MHz typical with CCLK = 100pF. 2 CS Chip Select, active low.
PAGE 8
MAX197 Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface _______________Detailed Description Converter Operation The MAX197, a multi-range, fault-tolerant ADC, uses successive approximation and internal input track/hold (T/H) circuitry to convert an analog signal to a 12-bit digital output. The parallel-output format provides easy interface to microprocessors (µPs). Figure 3 shows the MAX197 in its simplest operational configuration.
PAGE 9
Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface Input Format The control byte is latched into the device, on pins D7–D0, during a write cycle. Table 2 shows the controlbyte format. Even with VDD = 0V, the input resistive network provides current-limiting that adequately protects the device. Output Data Format The output data format is binary in unipolar mode and twos-complement binary in bipolar mode. When reading the output data, CS, and RD must be low.
PAGE 10
MAX197 Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface Writing a new control byte during conversion cycle will abort conversion and start a new acquisition interval. Table 6.
PAGE 11
Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface MAX197 tCSRS tCS tCSRH CS tCSWS tWR tACQI tCSHW tCONV WR tDH tDS D7–D0 CONTROL BYTE ACQMOD = "1" CONTROL BYTE ACQMOD = "0" tINT1 INT RD HBEN tD01 tD0 HIGH / LOW BYTE VALID DOUT tTR HIGH / LOW BYTE VALID Figure 6. Conversion Timing Using External Acquisition Mode Clock Modes The MAX197 operates with either an internal or an external clock.
PAGE 12
MAX197 Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface External Clock Mode Select external clock mode by writing the control byte with D7 = 0 and D6 = 0. Figure 8 shows CLK and WR timing relationships in internal and external acquisition modes, with an external clock. A 100kHz to 2.0MHz external clock with 45% to 55% duty cycle is required for proper operation.
PAGE 13
Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface Power-On Reset At power-up, the internal power-supply circuitry sets INT high and puts the device in normal operation/external clock mode. This state is selected to keep the internal clock from loading the external clock driver when the part is used in external clock mode. Internal or External Reference The MAX197 can operate with either an internal or an external reference.
PAGE 14
MAX197 Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface Power-Down Mode To save power, you can put the converter into lowcurrent shutdown mode between conversions. Two programmable power-down modes are available, in addition to a hardware shutdown. Select STBYPD or FULLPD by programming PD0 and PD1 in the input control byte. When software power-down is asserted, it becomes effective only after the end of conversion.
PAGE 15
Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface Layout, Grounding, and Bypassing Careful printed circuit board layout is essential for best system performance. For best performance, use a ground plane. To reduce crosstalk and noise injection, keep analog and digital signals separate. Digital ground lines can run between digital signal lines to minimize interference. Connect analog grounds and DGND in a star configuration to AGND.
PAGE 16
MAX197 Multi-Range (±10V, ±5V, +10V, +5V), Single +5V, 12-Bit DAS with 8+4 Bus Interface _________________________________________________________Functional Diagram REF REFADJ AV = 1.638 CH7 CH6 CH5 CH4 CH3 CH2 CH1 SIGNAL CONDITIONING BLOCK AND OVERVOLTAGE TOLERANT MUX 10kΩ +2.