Analog Devices Inc./Maxim Integrated MAX1935ETA+T

Overview

MAX1935ETA+T from Maxim Integrated is a low-dropout linear regulator with PMOS pass transistor, delivering guaranteed 500mA output current at ≤175mV dropout (at 500mA), ±1.5% output voltage accuracy, and adjustable output range from 0.8V to 4.5V via external resistor divider - used in portable power rails for USB hubs, docking stations, and cellular handsets.

For engineers reviewing the MAX1935ETA+T datasheet, MAX1935ETA+T pinout, MAX1935ETA+T application, or MAX1935ETA+T equivalent, key selection criteria include dropout voltage at full load, shutdown current (0.02µA), POK threshold accuracy (93% of VOUT), thermal shutdown behavior (170°C), and DFN-8 package thermal performance (θJA = 41°C/W).

Technical Context

The MAX1935ETA+T employs an internal 0.8V reference and error amplifier driving a 0.4Ω P-channel MOSFET pass transistor, enabling low-quiescent operation without base-drive current. Its dual-mode feedback architecture selects between factory-trimmed preset mode (SET = GND) and adjustable mode (SET biased at 780–820mV) based on SET pin voltage.

Power-OK (POK) is an open-drain output asserting low when VOUT falls below 93% of nominal regulation; shutdown (SHDN) disables regulation and reduces IQ to 0.02µA while forcing POK low. Thermal protection activates at +170°C with +20°C hysteresis, and short-circuit current limit is specified at 600–2500mA.

Key Specifications

Pinout & Package

MAX1935ETA+T is housed in an 8-pin 3mm × 3mm thin DFN package with exposed thermal pad (TDFN-EP), optimized for high-power-density portable designs. The package supports θJA = 41°C/W on a four-layer board and requires soldering the exposed pad to PCB ground for thermal integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout linear regulator applications.

Compared with TPS79533DCQ and MCP1825-3302E/DB, the MAX1935ETA+T uniquely combines adjustable output (0.8V–4.5V), ultra-low dropout (175mV), integrated POK, and 0.02µA shutdown - making it optimal for compact, multi-rail, battery-critical systems requiring precise power sequencing and minimal leakage.

Availability

MAX1935ETA+T is available at Aetrix Electronics and suitable for notebook computers, cellular telephones, and USB hubs requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MAX1935ETA+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) designs precision analog, mixed-signal, and power-management ICs for industrial, computing, and communications markets.

The MAX1935ETA+T belongs to Maxim's low-dropout linear regulator product line, engineered specifically for space-constrained portable electronics demanding high output current, ultra-low quiescent power, and accurate power-good signaling.

FAQ

What is the maximum output current specification for the MAX1935ETA+T?

The MAX1935ETA+T guarantees 500mA continuous output current across its operating temperature range (-40°C to +85°C). This rating is validated under worst-case conditions including minimum input voltage (2.25V), maximum ambient temperature, and full thermal load. Short-circuit current limit is specified from 600mA to 2500mA, allowing indefinite safe shorting without damage. The MAX1935ETA+T maintains regulation stability up to this current when paired with proper input/output capacitors and PCB thermal design.

Does the MAX1935ETA+T support adjustable output voltage, and what is the range?

Yes, the MAX1935ETA+T supports adjustable output voltage from 0.8V to 4.5V using an external resistor divider connected between OUT and SET pins. The internal SET reference voltage is tightly regulated at 780–820mV over temperature and load. For example, selecting R2 = 49.9kΩ and R1 = 150kΩ yields a 3.3V output. The MAX1935ETA+T also operates in preset mode when SET is grounded, though the ETA+T variant itself is adjustable - preset versions carry suffixes like ETA15 (1.5V) or ETA33 (3.3V).

What is the function and electrical behavior of the POK pin on the MAX1935ETA+T?

The POK (Power-OK) pin on the MAX1935ETA+T is an open-drain, active-low output that asserts low when the regulated output voltage falls below 93% of its nominal value. It remains low until VOUT rises above this threshold, then transitions to high-impedance state. A 100kΩ pullup resistor to OUT is recommended to generate a logic-high signal for microcontrollers. During shutdown, POK is forced low regardless of VOUT. The MAX1935ETA+T specifies POK sink capability of 2mA and VOL ≤ 50mV, ensuring robust interfacing with standard logic inputs.

How does the MAX1935ETA+T achieve its low 175mV dropout voltage at 500mA?

The MAX1935ETA+T achieves 175mV dropout at 500mA through its integrated 0.4Ω P-channel MOSFET pass transistor, which eliminates base-drive current losses inherent in bipolar PNP designs. Dropout is calculated as VDROPOUT = RDS(ON) × ILOAD, resulting in minimal conduction loss. This architecture sustains regulation even as input voltage approaches VOUT + 0.175V - critical for maximizing battery utilization in single-cell Li-ion systems. The MAX1935ETA+T maintains this performance across -40°C to +85°C, with linear interpolation applied for outputs between 2.25V and 4.0V.

What thermal management requirements apply to the MAX1935ETA+T in high-load operation?

The MAX1935ETA+T requires connection of its exposed thermal pad to the PCB ground plane via multiple vias or a large copper area to maintain junction temperature below +150°C. With θJA = 41°C/W on a four-layer board, dissipating 1.95W (maximum rated) raises junction temperature by ~80°C above ambient - so at +70°C ambient, TJ reaches ~150°C. Derating is required above +70°C ambient (24.4mW/°C). The MAX1935ETA+T includes thermal shutdown at +170°C with +20°C hysteresis, but continuous operation must stay within absolute max ratings. Proper layout is mandatory for full 500mA output capability.