MAX1491CNI+

ADCs/DACs - Special Purpose Overview

The MAX1491CNI+ is a low-power, single-chip analog-to-digital converter (ADC) with an integrated liquid crystal display (LCD) driver. It provides 3.5-digit resolution (±1999 count) using a sigma-delta architecture. The device operates from a single 2.7V to 5.25V supply and includes an internal 2.048V reference, high-accuracy oscillator, and charge pump for negative supply generation. It features selectable input ranges of ±2V or ±200mV, on-chip buffers for high-impedance sources, and >100dB rejection of 50Hz/60Hz line noise. The part is housed in a 28-pin DIP package and operates over the 0°C to +70°C temperature range.

ADCs/DACs - Special Purpose Feature Summary

• Sigma-Delta ADC Architecture: Eliminates external integrating or auto-zero capacitors.
• Integrated LCD Driver: Triplexed driver supports 3.5-digit displays with segment and backplane outputs.
• High Noise Rejection: Offers >100dB simultaneous rejection of 50Hz and 60Hz line frequencies.
• Internal Charge Pump: Generates VNEG (-2.42V typ) to power input buffers for single-supply operation.

ADCs/DACs - Special Purpose Applications

• Digital Panel Meters
• Hand-Held Meters
• Digital Voltmeters
• Digital Multimeters

ADCs/DACs - Special Purpose Procurement Notes

Verify the suffix 'CNI+' indicates the commercial temperature range (0°C to +70°C) and 28-pin DIP package configuration. Confirm RoHS compliance status through official manufacturer documentation prior to integration. Ensure the ordering code matches the specific pinout and resolution requirements for the target design.

ADCs/DACs - Special Purpose Selection Notes

Select this component for applications requiring direct LCD interfacing without external microcontrollers. The ±200mV range offers higher resolution for small signals, while the ±2V range suits broader measurements. Verify that the source impedance remains within limits for the internal buffers and that the supply voltage stays between 2.7V and 5.25V.

ADCs/DACs - Special Purpose Part Context

This part belongs to the MAX1491/MAX1493/MAX1495 family of single-chip ADCs with LCD drivers. While the MAX1493 and MAX1495 provide 4.5-digit resolution in TQFP packages, the MAX1491 variant specifically delivers 3.5-digit resolution. The 'C' denotes the commercial temperature range, and 'NI' specifies the 28-pin DIP package style.

ADCs/DACs - Special Purpose Replacement Considerations

Direct replacements within the same family include the MAX1491CAI (SSOP package). For higher resolution needs, the MAX1493CCJ or MAX1495CCJ offer 4.5-digit performance in a 32-pin TQFP package. Package pinouts differ significantly between DIP, SSOP, and TQFP variants; verify mechanical compatibility before substitution.

ADCs/DACs - Special Purpose FAQ

How does the MAX1491 handle negative input voltages?

An internal charge pump generates a negative supply voltage (VNEG) at the VNEG pin. This allows the analog input buffers to accept bipolar signals ranging from -2.2V to +2.2V relative to ground.

What is the conversion rate of the device?

The device operates at a fixed conversion rate of 5Hz, corresponding to the SINC4 digital filter's settling time of four output data periods.

Can the device use an external voltage reference?

Yes. By connecting the INTREF pin to GND, the device switches to external reference mode. In this mode, REF+ and REF- must be bypassed to GND with capacitors >= 0.1µF.