Analog Devices Inc./Maxim Integrated MAX121CPE

Overview

The MAX121CPE from Maxim Integrated is a 14-bit, 308ksps successive-approximation analog-to-digital converter (ADC) with integrated track/hold, ±5V bipolar input range, 78dB SINAD, and -85dB THD. It operates from +5V and -12V/-15V supplies, consumes 210mW, and interfaces directly to TMS320, ADSP2101, and µPD77230 DSPs via SPI/QSPI-compatible serial output. It targets high-fidelity signal acquisition in real-time digital signal processing systems.

For engineers reviewing the MAX121CPE datasheet, MAX121CPE pinout, MAX121CPE application, or MAX121CPE equivalent, key selection considerations include its 2.9µs conversion time, ±15V overvoltage-tolerant analog input, buried-zener -5V reference with 30ppm/°C drift, TTL/CMOS-compatible 1.1–5.5MHz clock interface, and support for three distinct operational modes (CONVST-, CS-, or continuous-triggered).

Technical Context

The MAX121CPE implements a BiCMOS SAR architecture with on-chip track/hold and a low-drift buried-zener reference, enabling simultaneous high speed (308ksps) and precision (±2 LSB INL, ±1.5 LSB DNL). Its dual-supply operation (+5V VDD, -12V/-15V VSS) supports true bipolar signal capture without external level-shifting.

It delivers serial two's-complement output via SDATA, synchronized by SCLK and framed by SFRM or FSTRT - configurable via INVCLK and INVFRM pins. Three hardware-selectable modes (MODE = VDD/DGND, CONVST/CS control) allow flexible integration with microprocessors, DSPs, and FIFO/DMA-based data loggers.

Key Specifications

Pinout & Package

The MAX121CPE is housed in a 16-pin plastic DIP (Dual In-line Package) with 0.3-inch body width, compatible with standard through-hole PCB assembly and socketing for prototyping.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 14-bit, DSP-interface ADC applications.

Compared with ADS8322IPFB and AD7865BSZ-1, the MAX121CPE uniquely integrates track/hold, -5V buried-zener reference, and DSP-optimized serial framing in a single 16-pin DIP - reducing component count and simplifying timing-critical designs where 308ksps and ±5V bipolar input are sufficient.

Availability

The MAX121CPE is available at Aetrix Electronics and suitable for digital signal processing, audio/telecom processing, speech recognition, and DSP servo control applications requiring stable component supply across industrial temperature ranges (0°C to +70°C).

Supply support for MAX121CPE 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and computing markets.

The MAX121CPE belongs to Maxim's precision high-speed data acquisition product line, designed specifically for embedded DSP systems needing compact, low-glue, serial-output ADCs with integrated references and robust analog front-ends.

FAQ

What is the operating temperature range for the MAX121CPE?

The MAX121CPE is specified for commercial-grade operation from 0°C to +70°C. This is indicated by the "C" suffix in the part number and confirmed in the Absolute Maximum Ratings table. The device supports reliable performance across this full range when operated within its specified supply voltages (+4.75V to +5.25V on VDD, -10.8V to -15.75V on VSS) and clock frequency (0.1MHz to 5.5MHz). Thermal derating applies above +70°C per package-specific power dissipation limits.

Does the MAX121CPE require an external reference voltage?

No, the MAX121CPE does not require an external reference voltage because it includes an internal -5.00V buried-zener reference accessible at the VREF pin. This reference is factory-trimmed and provides ±30ppm/°C temperature drift. An external reference can be used only if it falls within -5.05V to -5.10V and can sink ≥5mA - but doing so overrides the internal reference and forfeits its stability advantages. For most applications, the internal reference is preferred and must be properly bypassed with 22µF || 0.1µF capacitors to AGND.

How does the MAX121CPE interface with SPI-compatible processors?

The MAX121CPE interfaces with SPI-compatible processors using its SDATA, SCLK, SFRM, and FSTRT signals - configured with MODE = VDD and INVCLK/INVFRM set appropriately. Since it outputs 16-bit frames (14 data + 2 zeros) while standard SPI reads 8 bits, two consecutive byte reads are required. The processor must drive CONVST low to initiate conversion, then read the MSB byte followed by the LSB byte within ≤160µs to avoid T/H droop errors. Clock rates up to 2MHz are supported in SPI mode, with data latched on the falling clock edge (CPHA = 1).

What are the power supply requirements for the MAX121CPE?

The MAX121CPE requires two independent supplies: +5V (VDD, 4.75V to 5.25V) and -12V or -15V (VSS, -10.8V to -15.75V). Total power dissipation is 210mW under typical conditions. Both supplies must be bypassed - VDD and VSS each to AGND with 10µF + 0.1µF capacitors - to ensure stable operation and low noise. AGND and DGND must be connected at a single point to prevent ground loops; separation preserves analog accuracy.

Can the MAX121CPE operate in continuous-conversion mode?

Yes, the MAX121CPE supports continuous-conversion mode when MODE, CONVST, and CS are all tied to DGND. In this mode, it performs back-to-back conversions at a rate of one per 16 clock cycles (e.g., 308ksps at 5.5MHz CLKIN), ideal for streaming data to FIFOs or DMA buffers. Acquisition time remains 400ns, limiting maximum CLKIN to 5MHz in this mode. SFRM becomes static and unusable; FSTRT is used exclusively for framing. The T/H automatically re-enters track mode after each conversion completes.