Analog Devices Inc./Maxim Integrated MAX122BCNG

Overview

The MAX122BCNG from Maxim Integrated is a 12-bit, 333ksps BiCMOS sampling analog-to-digital converter with integrated track/hold and -5V buried-zener reference, designed for high-speed bipolar data acquisition in ±5V input systems. It operates from +4.75V to +5.25V and -10.8V to -15.75V supplies, delivers 70dB SINAD and -75dB THD (max), and supports 0.1MHz–5MHz TTL-compatible clock inputs.

For engineers reviewing the MAX122BCNG datasheet, MAX122BCNG pinout, MAX122BCNG application, or MAX122BCNG equivalent, this page provides verified electrical parameters, mode-specific timing behavior, bipolar two's-complement output format, 24-pin narrow DIP package details, and validated alternatives for signal-chain design in telecom and spectrum analysis.

Technical Context

The MAX122BCNG uses successive approximation architecture with an internal track/hold circuit that achieves 350ns acquisition time and fixed 2.6µs conversion time (13–14 clock cycles). Its -5V reference output exhibits ±25ppm/°C drift over 0°C to +70°C and requires 22µF || 0.1µF bypassing at VREF–AGND.

It supports five µP interface modes-including full-control (mode 1), stand-alone (mode 2), slow-memory (mode 3), ROM (mode 4), and continuous-conversion (mode 5)-with MODE pin hardwired to set INT/BUSY polarity and operational state. All digital I/Os are TTL/CMOS compatible, and bus timing meets standard microprocessor access requirements without wait states.

Key Specifications

Pinout & Package

MAX122BCNG is housed in a 24-pin narrow plastic DIP (PDIP) package, RoHS-compliant and lead-free, with 0.3-inch body width and through-hole mounting. Pin pitch is 0.1 inch; pin 1 marked by notch or dot.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit, medium-speed ADC applications.

Compared with ADS7800U and MAX125CEAX, the MAX122BCNG offers optimal balance of integrated functionality (T/H + reference), compact DIP package, and proven 333ksps performance in cost-sensitive, space-constrained bipolar acquisition systems.

Availability

MAX122BCNG is available at Aetrix Electronics and suitable for telecom signal digitization, audio processing front-ends, spectrum analyzer acquisition, data logging for industrial sensors, and high-speed data acquisition requiring stable component supply and long-term obsolescence management.

Supply support for MAX122BCNG includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and high-frequency ICs for industrial, medical, communications, and consumer applications.

The MAX120/MAX122 product line was engineered specifically for high-throughput, bipolar-input data acquisition systems where integration of track/hold, reference, and µP interface reduces bill-of-materials and improves signal-chain accuracy.

FAQ

What is the maximum clock frequency supported by the MAX122BCNG?

The MAX122BCNG supports a maximum clock frequency of 5MHz, as specified in its Electrical Characteristics table. This limit ensures proper operation of the internal successive approximation register and track/hold circuitry across the full temperature range. Operating above 5MHz may cause timing violations, incomplete conversions, or degraded AC performance such as reduced SINAD. The minimum clock frequency is 0.1MHz, constrained by the T/H droop rate. For reliable 333ksps throughput, a 5MHz clock is recommended.

Does the MAX122BCNG require external components for basic operation?

Yes - the MAX122BCNG requires external decoupling capacitors on VDD, VSS, and VREF pins. Specifically, VREF must be bypassed to AGND with a 22µF electrolytic capacitor (ESR ≤100mΩ) in parallel with a 0.1µF ceramic capacitor. VDD and VSS each require at least a 0.1µF ceramic capacitor close to the pins. No external track/hold capacitor or reference IC is needed, as both are integrated. External passive components are limited to these bypass elements and optional gain/offset trim networks.

How does the MODE pin affect the INT/BUSY output behavior of the MAX122BCNG?

The MODE pin configures the function of the INT/BUSY pin on the MAX122BCNG. When MODE is tied to VDD, INT/BUSY acts as an interrupt output: it goes low upon conversion completion and returns high after data is read. When MODE is left open or tied to DGND, INT/BUSY functions as a busy flag: it goes low at conversion start and remains low until conversion completes and data is valid. This dual-mode flexibility allows the MAX122BCNG to interface with both interrupt-driven and polling-based microprocessor systems without external logic.

What is the analog input impedance and overvoltage tolerance of the MAX122BCNG?

The MAX122BCNG analog input (AIN) presents an impedance of 6kΩ in parallel with 10pF, as defined by its internal sampling architecture. It is overvoltage tolerant to ±15V relative to AGND - meaning it can withstand transient excursions beyond its normal ±5V input range without damage or latch-up. This tolerance applies under all operating conditions and is validated per Absolute Maximum Ratings. However, sustained operation outside ±5V will not yield valid conversion results and may degrade long-term reliability if repeated frequently.

Can the MAX122BCNG operate with an external reference voltage?

Yes - the MAX122BCNG can accept an external reference voltage applied to the VREF pin, provided it falls within -5.05V to -5.10V and can sink at least 5mA. The internal buried-zener reference is overdriven in this configuration, allowing improved stability or temperature performance if a higher-grade external reference is used. The same 22µF || 0.1µF bypass network remains mandatory at VREF–AGND. Using an external reference does not alter the ADC's transfer function or code width; 1 LSB still equals 2.44mV (10V/4096) for the ±5V full-scale range.