Microcontroller-Interface, 4.5-/3.5-Digit Panel Meters with 4-20mA Output

The MAX1366/MAX1368 low-power, 4.5- and 3.5-digit, panel meters feature an integrated sigma-delta analog-to-digital converter (ADC), LED display drivers, voltage digital-to-analog converter (DAC), and a 4–20mA (or 0 to 16mA) current driver.

The MAX1366/MAX1368's analog input voltage range is programmable to either ±2V or ±200mV. The MAX1368 drives a 3.5-digit (±1999 count) display and the MAX1366 drives a 4.5-digit (±19,999 count) display. The ADC output directly drives the LED display as well as the voltage DAC, which, in turn, drives the 4–20mA (or 0 to 16mA) current-loop output.

In normal operation, the 0 to 16mA/4–20mA current-loop output follows the ±2V or ±200mV analog input to drive remote panel-meter displays, data loggers, and other industrial controllers. For added flexibility, the MAX1366/MAX1368 allow direct access to the ADC result, DAC output, and the V/I converter input.

The sigma-delta ADC does not require external precision integrating capacitors, autozero capacitors, crystal oscillators, charge pumps, or other circuitry commonly required in dual-slope ADC panel-meter circuits. On-chip analog input and reference buffers allow direct interface with high-impedance signal sources. Excellent common-mode rejection and digital filtering provides greater than 100dB rejection of simultaneous 50Hz and 60Hz line noise. Other features include data hold and peak detection and overrange/underrange detection.

The MAX1366/MAX1368 require a 2.7V to 5.25V supply, a 4.75V to 5.75V V/I supply, and a 7V to 30V loop supply. They are available in a space-saving (7mm x 7mm), 48-pin TQFP package and operate over the extended (-40°C to +85°C) temperature range.

Applications

* Automated Test Equipment (ATE) * Data Acquisition Systems * Digital Multimeters * Digital Panel Meters * Digital Voltmeters * Industrial Process Control

* Microcontroller (µC)-Interface, Digital Panel Meter

* 20-Bit Sigma-Delta ADC

* 4.5-Digit Resolution (±19,999 Count, MAX1366)

* 3.5-Digit Resolution (±1999 Count, MAX1368)

* No Integrating/Autozeroing Capacitors

* 100MΩ Input Impedance

* ±200mV or ±2.000V Input Range

* LED Display

* Common-Cathode 7-Segment LED Driver

* Programmable LED Current (0 to 20mA)

* 2.5Hz Update Rate

* Output DAC and Current Driver

* ±15-Bit DAC with 14-Bit Linear V/I Converter

* Selectable 0 to 16mA or 4–20mA Current Output

* Unipolar/Bipolar Modes

* ±50µA Zero Scale, ±40ppmFS/°C (typ)

* ±0.5% Gain Error, ±25ppmFS/°C (typ)

* Separate 7V to 30V Supply for Current-Loop Output

* 2.7V to 5.25V ADC/DAC Supply

* 4.75V to 5.25V V/I Converter Supply

* Internal 2.048V Reference or External Reference

* SPI™-/QSPI™-/MICROWIRE™-Compatible Serial Interface

* 48-Pin, 7mm x 7mm TQFP Package