MAX187/MAX189 - 12-Bit Serial Analog-to-Digital Converter (ADC)

Overview

The MAX187 and MAX189 are high-performance, 12-bit analog-to-digital converters (ADCs) designed for precision data acquisition applications. These devices feature a serial interface, making them ideal for space-constrained or microcontroller-based systems. With low power consumption and high accuracy, the MAX187/MAX189 are suitable for a wide range of industrial, medical, and instrumentation applications.

The MAX187 operates with a single +5V supply, while the MAX189 offers flexibility with a +5V or ±5V supply range. Both devices include an internal sample-and-hold (T/H) circuit, a precision voltage reference, and a serial interface compatible with SPI™, QSPI™, and Microwire™ standards.

Key Features

• 12-Bit Resolution: Provides high-precision conversion with excellent linearity.
• Serial Interface: SPI/QSPI/Microwire-compatible 3-wire interface reduces wiring complexity.
• Internal Reference: Integrated 4.096V voltage reference eliminates the need for external components.
• Low Power Consumption: Typically consumes 2mA during operation and 2µA in shutdown mode.
• Single-Supply Operation (MAX187): Operates from a single +5V supply.
• Dual-Supply Operation (MAX189): Supports ±5V supplies for bipolar input ranges.
• Internal Sample-and-Hold: No external T/H circuit required.
• Small Package Options: Available in 8-pin DIP and SO packages.

Applications

The MAX187/MAX189 are versatile ADCs suitable for numerous precision measurement applications, including:

• Industrial process control systems
• Medical instrumentation
• Data acquisition systems
• Battery-powered portable devices
• Temperature measurement and control
• Pressure and strain gauge monitoring
• Automotive sensor interfaces

Electrical Characteristics

Absolute Maximum Ratings

• VDD (MAX187): +6V
• VDD (MAX189): +6V
• VSS (MAX189): -6V
• Analog Input Voltage: VSS - 0.3V to VDD + 0.3V
• Digital Input Voltage: -0.3V to VDD + 0.3V
• Operating Temperature Range: -40°C to +85°C
• Storage Temperature Range: -65°C to +150°C

DC Characteristics (VDD = +5V, TA = +25°C, unless otherwise noted)

• Resolution: 12 bits
• Integral Nonlinearity (INL): ±1 LSB (max)
• Differential Nonlinearity (DNL): ±1 LSB (max)
• Full-Scale Error: ±2 LSB (max)
• Zero-Scale Error: ±1 LSB (max)
• Reference Voltage: 4.096V ±1%
• Reference Temperature Coefficient: 25ppm/°C (typ)
• Power Supply Rejection Ratio (PSRR): 60dB (typ)

AC Characteristics

• Conversion Time: 10µs (max)
• Throughput Rate: 75ksps (max)
• Aperture Delay: 50ns (typ)
• Aperture Jitter: 5ns (typ)
• Signal-to-Noise Ratio (SNR): 72dB (typ)

Power Requirements

• Supply Voltage (MAX187): +4.5V to +5.5V
• Supply Voltage (MAX189): ±4.5V to ±5.5V
• Supply Current (Operating): 2mA (typ)
• Supply Current (Shutdown): 2µA (typ)

Package Information

The MAX187/MAX189 are available in the following package options:

• 8-Pin Plastic DIP (MAX187ACPA, MAX189ACPA)
• 8-Pin SOIC (MAX187ACSA, MAX189ACSA)

Pin Configuration (8-Pin DIP/SOIC)

• Pin 1 (VDD): Positive supply voltage (+5V)
• Pin 2 (AIN): Analog input
• Pin 3 (SHDN): Shutdown control input (active low)
• Pin 4 (VSS): Negative supply voltage (GND for MAX187, -5V for MAX189)
• Pin 5 (DOUT): Serial data output
• Pin 6 (CS): Chip select input (active low)
• Pin 7 (SCLK): Serial clock input
• Pin 8 (REF): Reference buffer output/reference input

Functional Description

The MAX187/MAX189 perform 12-bit successive-approximation analog-to-digital conversions. The conversion process begins when CS is pulled low, initiating the sampling of the analog input. The internal T/H circuit holds the input voltage, and the conversion starts on the falling edge of SCLK. The 12-bit result is output serially on DOUT, MSB first.

The devices feature a power-saving shutdown mode activated by pulling SHDN low. In shutdown, supply current drops to 2µA (typ), making these ADCs ideal for battery-powered applications.

Typical Application Circuit

A basic application circuit for the MAX187 includes:

• 0.1µF bypass capacitor between VDD and GND
• 10µF tantalum capacitor between REF and GND
• SPI-compatible microcontroller interface
• Analog input filtering (optional RC network)

Ordering Information

• MAX187ACPA: 8-pin Plastic DIP, Commercial Temperature Range
• MAX187ACSA: 8-pin SOIC, Commercial Temperature Range
• MAX189ACPA: 8-pin Plastic DIP, Commercial Temperature Range
• MAX189ACSA: 8-pin SOIC, Commercial Temperature Range