Analog Devices Inc./Maxim Integrated MAX494EPD+

Overview

MAX494EPD+ from Maxim Integrated is a quad micropower operational amplifier with rail-to-rail input and output swing, operating from +2.7V to +6V single supply or ±1.35V to ±3V dual supplies. It delivers 500kHz gain-bandwidth, 150µA per amplifier quiescent current, 200µV max input offset voltage, and drives 1kΩ loads - ideal for low-voltage signal conditioning in portable instrumentation and battery-powered data acquisition systems.

For engineers reviewing the MAX494EPD+ datasheet, MAX494EPD+ pinout, MAX494EPD+ application, or MAX494EPD+ equivalent, key selection criteria include rail-to-rail common-mode range (VEE to VCC), output swing within 50mV of rails at 100kΩ, unity-gain stability, no phase reversal on overdrive, and compatibility with capacitive loads >1nF.

Technical Context

The MAX494EPD+ integrates four independent precision op amps on a single die, each featuring complementary NPN/PNP input stages enabling true rail-to-rail input common-mode voltage (VEE – 0.25V to VCC + 0.25V) and output swing (within 50mV of VEE/VCC at 100kΩ). Its folded-cascode architecture supports high DC accuracy while maintaining low power consumption.

It operates without phase reversal when inputs exceed supply rails, includes internal back-to-back diode protection (±0.7V differential limit), and achieves stable operation driving ≥1000pF capacitive loads - a critical advantage over standard CMOS rail-to-rail amplifiers in ADC buffering and sensor interface applications.

Key Specifications

Pinout & Package

MAX494EPD+ is housed in a 14-pin plastic DIP package (0.300" wide), compatible with industry-standard through-hole prototyping and legacy PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad rail-to-rail op amp applications.

Compared with TLV2464IDR and AD8604ARUZ, MAX494EPD+ uniquely balances micropower operation (150µA), rail-to-rail performance across full 2.7V–6V range, and guaranteed no-phase-reversal behavior - making it irreplaceable in battery-critical, wide-supply, fault-tolerant sensor interfaces.

Availability

MAX494EPD+ is available at Aetrix Electronics and suitable for portable medical sensors, battery-powered data loggers, and industrial sensor signal chains requiring stable component supply and long-term obsolescence management.

Supply support for MAX494EPD+ 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 power management ICs for demanding industrial, medical, and communications applications.

The MAX492/MAX494/MAX495 family was engineered specifically for ultra-low-power, rail-to-rail signal conditioning in battery-operated and low-voltage systems - prioritizing DC accuracy, supply flexibility, and robustness over raw speed.

FAQ

What is the maximum capacitive load the MAX494EPD+ can drive without oscillation?

The MAX494EPD+ remains stable driving ≥1000pF pure capacitive loads under unity-gain conditions, as verified in Figure 6 of the datasheet. Stability is further enhanced when sourcing or sinking currents significantly above or below ~100µA. For marginal cases, adding a 47Ω series isolation resistor (Figure 9b) extends stability to 10,000pF. This capability eliminates external compensation in ADC input buffers and piezoelectric transducer interfaces.

Does the MAX494EPD+ support true rail-to-rail input common-mode voltage?

Yes, the MAX494EPD+ accepts input common-mode voltages from VEE – 0.25V to VCC + 0.25V, confirmed in the Absolute Maximum Ratings and DC Electrical Characteristics tables. Unlike many rail-to-rail op amps, it maintains functionality and avoids phase reversal even when inputs exceed supply rails - a critical feature for fault-tolerant sensor front-ends and battery voltage monitoring circuits where signals may transiently go beyond VCC or below VEE.

Is external offset nulling possible on the MAX494EPD+?

No, external offset nulling is not supported on the MAX494EPD+. The datasheet explicitly states that offset adjustment is only available on the single MAX495 (via pins 1 and 5) and not on the dual MAX492 or quad MAX494 variants. The MAX494EPD+ relies on factory-trimmed offset (200µV max at +25°C) and achieves sufficient accuracy for most 12-bit ADC applications without trimming - for example, contributing <0.5 LSB error with a 4.096V reference.

What is the recommended power supply bypassing for the MAX494EPD+?

Maxim specifies a 1µF tantalum (or ceramic) capacitor in parallel with a 0.1µF ceramic capacitor directly at the VCC and VEE pins of the MAX494EPD+. This dual-capacitor network suppresses both low-frequency supply droop and high-frequency noise, ensuring stable operation in battery-powered systems. Layout best practices require minimizing trace length between capacitors and pins, and placing components adjacent to the DIP package - especially critical given the device's sensitivity to supply noise (110dB PSRR).

Why is the MAX494EPD+ marked "Not Recommended for New Designs"?

The MAX494EPD+ is marked "Not Recommended for New Designs" because its wafer fabrication process has been discontinued by Maxim's external foundry. While fully functional and supported for existing designs, Maxim advises new projects to evaluate modern alternatives like the MAX44260 or AD8604 - which offer improved specs and active manufacturing. Aetrix Electronics maintains inventory and provides lifecycle coordination, including last-time-buy planning and cross-reference guidance for migration paths.