3.5- and 4.5-Digit, Single-Chip ADCs with LCD Drivers

The MAX1492/MAX1494 low-power, 3.5- and 4.5-digit, analog-to-digital converters (ADCs) with integrated liquid crystal display (LCD) drivers operate from a single 2.7V to 5.25V power supply. They include an internal reference, a high-accuracy on-chip oscillator, and a triplexed LCD driver. An internal charge pump generates the negative supply needed to power the integrated input buffer for single-supply operation. The ADCs are configurable for either a ±2V or ±200mV input range and outputs its conversion results to an LCD and/or to a microcontroller (µC). µC communication is facilitated through an SPI™-/QSPI™-/MICROWIRE®-compatible serial interface. The MAX1492 is a 3.5-digit (±1999 count) device, and the MAX1494 is a 4.5-digit (±19,999 count) device.

The MAX1492/MAX1494 do not require external-precision integrating capacitors, autozero capacitors, crystal oscillators, charge pumps, or other circuitry required with dual-slope ADCs (commonly used in panel meter circuits).

These devices also feature on-chip buffers for the differential signal and reference inputs, allowing direct interface with high-impedance signal sources. In addition, they use continuous internal-offset calibration and offer > 100dB simultaneous rejection of 50Hz and 60Hz line noise. Other features include data hold and peak hold, overrange and underrange detection, and a low-battery monitor.

The MAX1494 comes in a 32-pin, 7mm x 7mm LQFP package, and the MAX1492 comes in 28-pin SSOP and 28-pin PDIP packages. All devices in this family operate over the 0°C to +70°C commercial temperature range.

Applications

* Digital Multimeters * Digital Panel Meters * Digital Voltmeters * Handheld meters

* High Resolution

* MAX1494: 4.5 Digits (±19,999 Count)

* MAX1492: 3.5 Digits (±1999 Count)

* Sigma-Delta ADC Architecture

* No Integrating Capacitors Required

* No Autozeroing Capacitors Required

* > 100dB of Simultaneous 50Hz and 60Hz Rejection

* Operate from a Single 2.7V or 5.25V Supply

* Selectable Input Range of ±200mV or ±2V

* Selectable Voltage Reference: Internal 2.048V or External

* Internal High-Accuracy Oscillator Needs No External Components

* Automatic Offset Calibration

* Low Power

* Maximum 960µA Operating Current

* Maximum 400µA Shutdown Current

* Small 32-Pin 7mm x 7mm LQFP Package (4.5 Digits), 28-Pin SSOP Package (3.5 Digits)

* Triplexed LCD Driver

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

* Evaluation Kit Available (Order MAX1494EVKIT)