Analog Devices Inc./Maxim Integrated MAX8668ETET+

Overview

The MAX8668ETET+ from Maxim Integrated is a dual step-down DC-DC converter with dual low-noise LDO regulators in a single 16-pin thin QFN (3mm × 3mm) package. It delivers 600mA on OUT1 and 1200mA on OUT2 (adjustable 0.6V–3.3V), plus two 300mA LDOs (OUT3/OUT4) operating down to 1.7V input, all with individual enables and 1.5MHz hysteretic-PWM control for ultra-small external components - ideal for powering microprocessor cores and I/O rails in smartphones and portable media devices.

For engineers reviewing the MAX8668ETET+ datasheet, MAX8668ETET+ pinout, MAX8668ETET+ application, or MAX8668ETET+ equivalent, key selection considerations include output voltage adjustability via FB1/FB2 resistive dividers, guaranteed current limits per rail, thermal shutdown at +160°C, no-load supply current of 100µA (all regulators enabled), and compatibility with 2.2µH chip inductors and ceramic output capacitors.

Technical Context

The MAX8668ETET+ integrates two synchronous step-down converters using a proprietary hysteretic-PWM architecture that maintains ~1.5MHz switching frequency across load range, enabling fast transient response and minimal external component count. Each buck stage features p-channel high-side switch and n-channel synchronous rectifier with on-resistance of 0.3–0.6Ω (OUT1) and 0.12–0.27Ω (OUT2), plus valley-current limiting and soft-start ramp time of 15–45µs.

Its dual LDOs (OUT3/OUT4) operate from 1.7V–5.5V input, deliver ±3% output accuracy over 1mA–300mA load, exhibit 75µV_RMS output noise (100Hz–100kHz), and provide 57dB PSRR below 1kHz - optimized for noise-sensitive analog and RF subsystems requiring clean, sequenced power rails.

Key Specifications

Pinout & Package

Package: 16-pin thin QFN, 3mm × 3mm, exposed paddle (EP) - requires solder connection to GND/PGND for thermal and electrical performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multi-rail power management applications.

Compared with TPS65023RSBR and ADP5022ACPZ-2-R7, the MAX8668ETET+ uniquely combines adjustable buck outputs with voltage positioning, ultra-low 100µA no-load current, and 1.5MHz operation optimized for minimal inductor size - making it optimal for space-constrained, battery-sensitive portable designs requiring fine-grained rail control.

Availability

MAX8668ETET+ is available at Aetrix Electronics and suitable for smartphone power management, portable media device subsystems, and handheld instrumentation requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for MAX8668ETET+ 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, automotive, communications, and consumer applications.

The MAX8668 is part of Maxim's portable power-management portfolio, designed specifically to consolidate multiple voltage rails in space- and power-constrained handheld devices while maintaining low noise, high efficiency, and flexible sequencing.

FAQ

What output voltage ranges does the MAX8668ETET+ support for its step-down regulators?

The MAX8668ETET+ supports adjustable output voltages from 0.6V to 3.3V on both OUT1 and OUT2, set via external resistor dividers connected to FB1 and FB2 pins. This adjustability is exclusive to the MAX8668 variant (not MAX8667). The internal 0.6V reference ensures tight regulation accuracy (±1.5% at +25°C, ±3% over –40°C to +85°C), and the voltage positioning feature allows intentional output droop under load to improve transient response without increasing output capacitance. The MAX8668ETET+ datasheet specifies minimum/maximum values and layout guidelines for stable operation across this full range.

How does the MAX8668ETET+ achieve low-noise power delivery for sensitive analog circuits?

The MAX8668ETET+ achieves low-noise power delivery primarily through its dual LDO regulators (OUT3 and OUT4), which deliver 75µV_RMS output noise (100Hz–100kHz) and 57dB power-supply rejection ratio (PSRR) below 1kHz. These LDOs operate from a dedicated 1.7V–5.5V input (IN34) and include internal p-channel pass transistors, precision error amplifiers, and factory-trimmed voltage dividers. Their low dropout (250mV max at 300mA) and ability to run from separate, filtered input rails isolate analog circuitry from switching noise generated by the buck converters - a key advantage confirmed in MAX8668ETET+ evaluation board measurements and application notes.

What is the purpose of the REF pin on the MAX8668ETET+, and how should it be used?

The REF pin on the MAX8668ETET+ provides a buffered, low-impedance 0.6V internal reference voltage (±1.5% tolerance at +25°C) derived from the bandgap circuit. It must be bypassed to GND with a 0.01µF ceramic capacitor to ensure stability and low noise. This reference serves two critical functions: (1) it sets the regulation point for the FB1/FB2 feedback networks controlling OUT1/OUT2 voltages, and (2) it can be used externally as a precision reference for ADCs, DACs, or comparator thresholds. Unlike generic reference ICs, the MAX8668ETET+ REF pin is not intended for high-current loads - its specified sink/source capability is limited to ±10µA, as documented in the Electrical Characteristics table.

Can the MAX8668ETET+ support independent power sequencing for its four outputs?

Yes, the MAX8668ETET+ supports fully independent power sequencing via four dedicated enable inputs: EN1 controls OUT1, EN2 controls OUT2, EN3 controls OUT3, and EN4 controls OUT4. Each is active-high and compatible with standard logic levels (VIH = 1.44V min, VIL = 0.4V max). When an EN pin is driven high, its corresponding regulator initiates a controlled soft-start (15–45µs ramp time); when driven low, the regulator shuts down and discharges its output through an internal 1kΩ resistor (for LDOs) or stops switching (for bucks). This granular control enables custom startup/shutdown sequences - for example, powering LDOs before bucks to bias control logic - without requiring external sequencers or firmware intervention.

What are the absolute maximum ratings for input voltage on the MAX8668ETET+ IN12 and IN34 pins?

The MAX8668ETET+ specifies absolute maximum ratings of –0.3V to +6.0V on IN12 and IN34 pins relative to GND. However, functional operation requires adherence to stricter recommended operating conditions: IN12 must be 2.6V to 5.5V (and ≥ IN34), while IN34 must be 1.7V to 5.5V (and ≤ IN12). Exceeding the 5.5V upper limit on either pin, even momentarily, risks permanent damage due to internal clamp diode conduction and package power dissipation limits. The datasheet explicitly warns that LX1/LX2 pins contain internal clamp diodes to GND and IN12 - forward-biasing these during abnormal operation (e.g., inductor flyback overshoot) must be carefully managed with proper snubbing and layout to avoid exceeding the 1667mW continuous power dissipation limit at +70°C.