Analog Devices Inc./Maxim Integrated MAX1605EUT-T

Overview

MAX1605EUT-T from Maxim Integrated is a 30V internal-switch boost converter in a 6-pin SOT23 package, operating from 2.4V to 5.5V VCC while boosting input as low as 0.8V up to 30V output. It integrates a 0.5A N-channel MOSFET with 1Ω on-resistance, supports selectable current limits (125/250/500mA), and delivers 88% efficiency at 10mA load-ideal for compact LCD bias generation in portable devices.

For engineers reviewing the MAX1605EUT-T datasheet, MAX1605EUT-T pinout, MAX1605EUT-T application, or MAX1605EUT-T equivalent, key selection criteria include its ultra-low 18μA quiescent current, 500kHz max switching frequency enabling miniature magnetics, adjustable feedback threshold (1.25V), and dual-supply capability (separate VIN and VCC rails).

Technical Context

The MAX1605EUT-T employs a minimum-off-time, current-limited control architecture with programmable peak inductor current via the LIM pin-enabling precise trade-offs between ripple, component size, and output power. Its internal 30V-rated N-channel MOSFET switch connects directly to LX, supporting high-voltage outputs without external high-side drivers.

It features independent supply rails: VCC powers the control circuitry (2.4V–5.5V), while VIN supplies the inductor (0.8V–30V), allowing operation from single-cell Li+ or NiMH batteries. Shutdown mode reduces supply current to 0.1μA and places LX in high-impedance state, though output remains coupled through the inductor-diode path.

Key Specifications

Pinout & Package

MAX1605EUT-T is housed in a 6-pin SOT23-6 package (3.0mm × 1.7mm, 0.95mm height), RoHS-compliant, with thermal pad not connected internally. Pin 1 is marked with AAHP laser code.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar boost converter applications.

Compared with MAX1605EUT-T, MAX1771ESA+ offers higher input flexibility but adds design complexity, while TPS61040DRVR achieves lower shutdown current at the expense of VIN/VCC separation and current-limit configurability-making MAX1605EUT-T optimal for space-constrained, multi-rail LCD bias where battery headroom and layout simplicity are critical.

Availability

MAX1605EUT-T is available at Aetrix Electronics and suitable for LCD bias generators, cellular phone displays, and palmtop computer power systems requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MAX1605EUT-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, medical, communications, and consumer applications.

The MAX1605 belongs to Maxim's high-voltage boost converter product line, engineered specifically for compact, low-power LCD bias generation in battery-operated portable electronics.

FAQ

What is the maximum output voltage achievable with the MAX1605EUT-T?

The MAX1605EUT-T supports output voltages up to 30V, as confirmed by its absolute maximum LX voltage rating of 30.5V and operational specification stating "VOUT = VIN to 30V". This is enabled by its internal 30V-rated N-channel MOSFET and feedback comparator referenced to 1.25V. Output voltage is set externally via resistor divider on the FB pin, and stability is maintained across the full range when using appropriate output capacitance and layout practices.

Can the MAX1605EUT-T operate from a single 1.5V alkaline cell?

Yes, the MAX1605EUT-T can operate from a single 1.5V alkaline cell because its inductor input voltage (VIN) range starts at 0.8V, independent of the VCC supply. The IC requires VCC to be 2.4V–5.5V, so a separate regulated 3.3V supply (e.g., from a low-dropout regulator) must power VCC, while the 1.5V cell directly feeds the inductor. This dual-rail architecture is explicitly supported in the datasheet's "Separate/Same Power for L1 and VCC" section.

How does the LIM pin affect efficiency and output ripple in the MAX1605EUT-T?

The LIM pin selects peak inductor current (125/250/500mA), directly influencing both efficiency and output ripple. At 125mA (LIM=GND), ripple decreases due to lower ΔI_L, enabling smaller inductors and capacitors-but efficiency drops ~3–5% at medium loads due to higher conduction losses relative to switching losses. At 500mA (LIM=VCC), efficiency peaks near 88% at 10mA, but ripple increases. The trade-off is documented in Figures toc06 and toc07 of the MAX1605 datasheet.

Does the MAX1605EUT-T provide output isolation during shutdown?

No, the MAX1605EUT-T does not isolate the output during shutdown. When SHDN is pulled low, the internal MOSFET turns off and LX goes high-impedance, but the output remains connected to VIN through the inductor and external Schottky diode, causing VOUT to decay to approximately VIN – 0.6V. For true isolation, the datasheet recommends adding an external PNP transistor (e.g., 2N2907A) in series with the output, as shown in Figure 5.

What is the recommended inductor value for a 18V/5mA output from a 3.6V input using the MAX1605EUT-T?

The datasheet specifies a 10µH inductor for the 18V/5mA typical operating circuit (Figure 3). This value balances size, ripple, and startup reliability: smaller inductors (e.g., 4.7µH) increase ripple and peak current stress; larger values (e.g., 47µH) reduce ripple but degrade light-load efficiency and may prevent startup at low VIN. The 10µH recommendation assumes 500mA current limit (LIM=VCC) and uses a shielded, 1.5A saturation-rated surface-mount inductor such as Coilcraft MSS5131-103ML.