3.5- and 4.5-Digit, Single-Chip ADCs with LED Drivers and µC Interface

The MAX1497/MAX1499 low-power, 3.5- and 4.5-digit, analog-to-digital converters (ADCs) with integrated lightemitting diode (LED) 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 multiplexed LED display driver. An internal charge pump generates the negative supply needed to power the integrated input buffers for single-supply operation. The ADC is configurable for either a ±2V or ±200mV input range and it outputs its conversion results to an LED and/or to a microcontroller (µC). Microcontroller communication is possible through an SPI™-/QSPI™- /MICROWIRE™-compatible serial interface. The MAX1497 is a 3.5-digit (±1999 count) device and the MAX1499 is a 4.5-digit (±19,999 count) device.

The MAX1497/MAX1499 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 rejection of 50Hz and 60Hz line noise. Other features include data hold and peak detection, overrange and underrange detection, and a user-programmable low-battery monitor.

The MAX1499 is available in a 32-pin, 7mm x 7mm TQFP package and the MAX1497 is available in 28-pin SSOP and 28-pin PDIP packages. All devices in this family operate over the -40°C to +85°C extended temperature range.

Applications

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

* High Resolution

* MAX1499: 4.5 Digits (±19,999 Count)

* MAX1497: 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 (Exclude LED Driver Current)

* Maximum 664µA Operating Current

* Maximum 268µA Shutdown Current

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

* Also Available in a PDIP Package (3.5 Digits)

* Multiplexed LED Drivers Resistor-Programmable Segment Current

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

* Extended Temperature Range (-40°C to +85°C)