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Maxim's panel meter ADCs with 4-20mA current output

Posted: 15 Mar 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Maxim Integrated Products? MAX1365? MAX1366? MAX1367? MAX1368?

Maxim Integrated Products introduced its new MAX1365-MAX1368 stand-alone panel meters that feature sigma-delta ADCs which digitize fully differential analog signals in the 2V and 200mV range and display the results with 3.5- or 4.5-digit resolution on a local LED display.

According to the press release, the new panel meters integrate a 4-20mA current transmitter to drive a remote panel-meter or other 4-20mA input. These devices are designed for industrial sensor applications and nonlinear measurements, with their high performance, integrated LED display drivers, and integrated 4-20mA output.

The MAX1365-MAX1368 also eliminate the need for sensitive and costly external components to achieve their high level of performance. Additionally, they may require external clock sources and external references to complete the system, Maxim said. Each panel meter device includes a 20bit sigma-delta ADC, an internal 2.048V reference and an internal oscillator, which means that they eliminate the need for precision external capacitors.

Additionally, the new products integrate a common-cathode 7-segment LED display driver, a 15bit DAC, and precision 4-20mA current transmitter. The current output is accurate to within 0.5 percent gain error and 10?A offset error. A fourth-order SINC4 digital filter simultaneously rejects 100dB of both 50Hz and 60Hz noise. On-chip input buffers provide 100-megaohm input impedance on the fully differential analog and reference inputs. Transparent offset calibration automatically corrects offset errors.

The integrated LED display on the stand-alone 4.5-digit MAX1365 and 3.5-digit MAX1367 shows the analog measurement while the 4-20mA current output transmits a signal proportional to the analog inputs. Both the MAX1366 and the MAX1368 ADCs provide a microcontroller interface which allows independent access and control of the ADC, LED display, and current output through a SPI-/QSPI-/MICROWIRE-compatible interface. This independent operation allows pre-processing of the ADC results before they appear on the LED display, explained Maxim.

The MAX1365-MAX1368 operate off a 2.7V to 5.25V ADC/DAC supply, 4.75V to 5.25V V/I converter supply, and a 7V to 30V supply for the 4-20mA current loop output. These devices are available in a 7-by-7mm, 48-pin TQFP package in the extended -40C to 85C temperature range. Prices start at $6.96 (1,000-up, FOB USA).

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