Analog Devices Inc./Maxim Integrated MAX1623EAP+T

Overview

MAX1623EAP+T from Maxim Integrated is a 3A, synchronous step-down DC-DC regulator with integrated 55mΩ PMOS and 60mΩ NMOS power switches, designed for 5V-to-3.3V/2.5V/adjustable local CPU and bus-termination supplies in notebook and desktop computers. It delivers ±1% output accuracy (including line/load regulation), 94% typical efficiency at full load, and supports switching frequencies up to 350kHz via external TOFF resistor programming.

For engineers reviewing the MAX1623EAP+T datasheet, MAX1623EAP+T pinout, MAX1623EAP+T application, or MAX1623EAP+T equivalent, key selection considerations include its constant-off-time current-mode PWM control, Idle Mode™ operation for light-load efficiency, pin-selectable fixed (3.3V/2.5V) or adjustable (1.1V–3.8V) output, and thermal shutdown protection at +145°C.

Technical Context

The MAX1623EAP+T implements constant-off-time, current-mode PWM control with an internal 1.10V ±1.5% reference and transconductance amplifier compensation at the COMP pin. Its PWM logic dynamically adjusts the PMOS on-time relative to a programmable off-time (0.5–4µs) set by R_TOFF, enabling stable regulation across input voltages from 4.5V to 5.5V.

Operation transitions seamlessly between PWM mode (>1.25A load) and Idle Mode™ (≤1.25A), where pulse-skipping reduces gate-charge and transition losses. Synchronous rectification eliminates external Schottky losses, while internal current sensing feeds three comparators for skip-threshold (1.25A), PWM current limit (4.15A max), and overload protection.

Key Specifications

Pinout & Package

MAX1623EAP+T is housed in a 20-pin SSOP (Shrink Small Outline Package) with exposed thermal pad (not electrically connected), optimized for high-current density and thermal performance on standard PCBs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Compared with TPS5430DR and RT8205AZSP, the MAX1623EAP+T uniquely combines ±1% output accuracy, integrated 1.10V reference, and hardware-selectable fixed/adjustable outputs - making it optimal for space-constrained, precision 5V-input computing applications where BOM simplicity and thermal efficiency are critical.

Availability

MAX1623EAP+T is available at Aetrix Electronics and suitable for notebook computer CPU I/O supplies, desktop bus-termination circuits, and DSP core power applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for MAX1623EAP+T 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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for computing, industrial, and communications markets.

The MAX1623EAP+T belongs to Maxim's high-efficiency, integrated power regulator product line, designed specifically for low-voltage, high-current point-of-load conversion in space- and thermally constrained computing platforms.

FAQ

What output voltage options does the MAX1623EAP+T support?

The MAX1623EAP+T supports three output configurations via the FBSEL pin: 3.33V (FBSEL left unconnected), 2.525V (FBSEL tied to VCC), or adjustable 1.1V–3.8V (FBSEL tied to GND or REF). In adjustable mode, output is set by a resistor divider from VOUT to GND with FB connected to the midpoint, where regulation occurs when V_FB = 1.10V. The MAX1623EAP+T achieves ±1% total accuracy across all modes.

How does the MAX1623EAP+T achieve high efficiency at light loads?

The MAX1623EAP+T enters Idle Mode™ below 1.25A load current, switching to pulse-skipping operation that reduces gate-charge and transition losses. This maintains >85% efficiency even at 10mA output, unlike fixed-frequency PWM regulators that suffer disproportionate switching loss at low loads. The MAX1623EAP+T's synchronous rectification further improves heavy-load efficiency by replacing Schottky losses with low-R_DS(ON) conduction.

Can the MAX1623EAP+T be used with input voltages outside 4.5V–5.5V?

No - the MAX1623EAP+T is strictly rated for 4.5V to 5.5V input per Absolute Maximum Ratings and Electrical Characteristics tables. Operation below 4.5V causes undervoltage lockout (UVLO threshold = 4.0V min), and exceeding 5.5V risks permanent damage to the IN-to-PGND and VCC-to-GND junctions. For wider input ranges, consider alternatives like the RT8205AZSP, but note its ±2% accuracy and lack of integrated reference.

What is the purpose of the REF pin on the MAX1623EAP+T?

The REF pin provides a buffered, precision 1.10V ±1.5% reference output usable as a system-level voltage source - for example, to bias external ADCs, comparators, or monitoring circuits. It can supply up to 10µA; however, loading beyond 5µA degrades both REF accuracy and main output regulation due to reference load-regulation error. The MAX1623EAP+T's REF pin is unique among comparable 3A buck regulators in offering this level of standalone reference stability.

How is switching frequency programmed on the MAX1623EAP+T?

Switching frequency is set by connecting a resistor (R_TOFF) from the TOFF pin to GND. The off-time follows t_OFF = R_TOFF/110kΩ (µs), adjustable from 0.5µs to 4µs, yielding frequencies up to 350kHz in continuous conduction mode. For example, 110kΩ gives ~1µs off-time and ~300kHz at 3.3V out from 5V in. The MAX1623EAP+T's constant-off-time architecture ensures stable operation without complex loop compensation adjustments.