Analog Devices Inc./Maxim Integrated MAX1993ETG+

Introduction to the MAX1993ETG+ Step-Down Controller

The MAX1993ETG+ from Analog Devices Inc./Maxim Integrated is a high-performance, positive-output, synchronous buck pulse-width modulation (PWM) controller optimized for powering up-to-date CPU cores, chipsets, and RAM power rails in notebook computers. Packaged in a 24-pin, 4x4mm TQFN, the MAX1993ETG+ is purpose-built for single-stage or two-stage step-down conversion from high-voltage batteries (2V to 28V) to low-voltage rails as low as 0.7V, while ensuring excellent transient response and high DC output accuracy over a wide range of input and output combinations.

Main Characteristics and Intended Uses of the MAX1993ETG+

The MAX1993ETG+ offers a suite of advanced capabilities crucial for contemporary mobile and computing designs:

Wide Input Range: 2V to 28V input enables direct buck conversion from prevalent notebook battery sources.

Flexible Output: Supports dynamically adjustable output from 0.7V to 5.5V—a necessity for on-the-fly voltage adjustments in chipsets and graphical processor cores.

Quick-PWM™ Architecture: Proprietary constant on-time, pseudo-fixed-frequency scheme combines fast transient response (100ns “instant-on” load response) and predictable switching behavior.

High Efficiency and MOSFET Drive: Robust gate drivers handle large, low-resistance MOSFETs to maximize efficiency in high-load applications.

Comprehensive Protection: Integrated inductor saturation, valley current-limit, overvoltage and undervoltage protection.

Digital Soft-Start and Power-Good Signaling: 1.7ms soft-start and windowed PGOOD output facilitate controlled power-up and system sequencing.

Primary applications include:

Notebook and ultraportable computers

Core/IO and single/dual-rail supplies for processors, chipsets, DRAM, including low-voltage rails

Advanced memory architectures, DDR memory termination (dynamic supply tracking)

Graphics processor and high-performance data path circuits requiring dynamic voltage selection

Circuit Structure and Working Mechanism of the MAX1993ETG+

At the heart of the MAX1993ETG+ lies the Quick-PWM control core, leveraging a constant on-time algorithm with input voltage feedforward. This approach, unlike traditional current- or voltage-mode controllers, times the high-side MOSFET “on” period based on the ratio of output to input voltage, with adaptive correction for losses in the power path. The result is nearly constant switching frequency across variable input scenarios and minimal response latency to output load changes.

Critical functions include:

On-time one-shot: Precisely sets switch conduction time; frequency programmable to 200, 300, 450, or 600kHz.

Dual operation modes: Pulse-skipping mode for high light-load efficiency and forced-PWM for low output ripple and sharper transient response, particularly during dynamic voltage change events.

Load-sensing: Valley current-limit technique utilizing either an external sense resistor or the low-side MOSFET’s RDS(ON); optional lossless inductor current sense also supported.

This architecture excels under scenarios such as rapid CPU power bursts or deep sleep-wake cycles, where a sluggish controller could otherwise cause undershoot or application instability.

Power Control Capabilities and Protection Features of the MAX1993ETG+

The MAX1993ETG+ integrates multi-layered power protection and management features to enhance system reliability and simplify power rail sequencing.

Inductor Saturation and Current-Limit

Adjustable valley current-limit threshold via external resistors (range: 25mV to 200mV).

Inductor saturation protection (LSAT pin): threshold selectable as a multiple of the current-limit, preventing prolonged overcurrent scenarios and protecting magnetic components under overload.

Fault Protection and System Status

Power-Good (PGOOD): Open-drain output signals healthy output regulation window (±10%); system controller can respond to “good” or “fault” signals for orderly power sequencing.

Soft-start: Digital ramping of current limit (phased over 1.7ms) to control inrush and avoid overshoot.

Overvoltage/undervoltage protection: Fast shutdown and output discharge via integrated low-ohm path; fault blanking ensures spurious events during dynamic output transitions are ignored.

Thermal protection: Automatic power-down and system latch-off when die temperature exceeds +160°C.

Regulation of Output Voltage and On-the-Fly Adjustment in the MAX1993ETG+

Designed expressly for environments such as dynamic voltage scaling (DVS) in modern CPUs, the MAX1993ETG+ provides:

External reference input (REFIN): Allows instantaneous digital adjustment of regulated output, with transition rates determined by external RC network.

Dynamic voltage transition management: During GATE transitions, forced-PWM operation and fault blanking are automatically asserted, minimizing voltage droop and false protection events.

Multiple output levels: Easily supports two or more output setpoints with logic/DAC intervention; essential for adaptive power architectures (e.g., sleep/run/boost modes in multicore SoCs).

Memory bus tracking: In DDR memory applications, output voltage can track system I/O rail for precise termination, with built-in support for current sink/source as mandated by DDR physical layer specs.

Sequential Design Steps for Incorporating the MAX1993ETG+

A robust MAX1993ETG+ design begins with a careful definition of application parameters and a sequential component selection procedure:

Define Input Voltage and Maximum Load: Analyze system power source margins (battery rails, adapter range) and maximum anticipated load for calculating duty cycle and stress points.

Select Switching Frequency: Balance efficiency (favoring lower frequencies for high VIN applications) with solution footprint (higher frequencies = smaller magnetics and capacitors).

Determine Inductor Value: Trade off between fast transient recovery (small L, large ripple), reduced output ripple (large L), and physical footprint. Design for peak and valley currents in line with controller protection thresholds.

Configure Output Voltage: Implement resistive dividers or dynamic reference logic as appropriate; always verify regulation points and margin for transient excursions.

Set Current-Limit and Saturation Thresholds: Select divider values and sense resistor for desired overcurrent cutoff. Enable inductor saturation protection if high inrush or overloads are anticipated.

Guidelines for Choosing Inductors, Capacitors, and MOSFETs for the MAX1993ETG+

Critical performance and reliability hinge on judicious component selection:

Inductor: Ferrite preferred for low losses; choose so that peak current (ILOAD(max) + ½ ripple) remains well below saturation and current limit. For lowest ripple, select L for 20%–50% ripple current at full load.

Output Capacitor: ESR must both limit output ripple and place ESR zero in a zone ensuring loop stability (≤50kHz typically). Polymer electrolytics or tantalum types generally work well; size is often dictated more by ESR than by capacitance.

Input Capacitor: Must comfortably handle RMS ripple current; ceramics, polymers, or low-ESR aluminum are suitable for stages directly off mechanical switches/batteries.

MOSFETs: Select the high-side device for balanced resistance (RDS(ON)) and manageable switching losses; low-side requires lowest RDS(ON) practical for conduction efficiency. Verify driver capabilities with total gate charge at selected switching frequency.

Use Cases and Practical Performance Assessment of the MAX1993ETG+

The MAX1993ETG+ is tailored for situations where power rail requirements are both demanding and dynamic, including:

Notebook platforms directly stepping down from 2to 28V battery packs to adaptive processor rails.

High-speed graphics subsystems requiring switching of core output voltages for power gating and turbo boost modes.

DDR memory or VTT termination rails, where termination voltage must track the I/O supply and both sourcing and sinking capability is critical.

Industrial or telecom modules where dynamic load conditions could trigger traditional controllers into instability or excessive voltage deviation.

In these environments, the adaptive on-time engine, robust protection, and surgical transient response of the MAX1993ETG+ provide reliability, system efficiency, and compact solution size.

Optimal PCB Design Practices for the MAX1993ETG+

Layout is essential to extracting full performance from the MAX1993ETG+:

Power paths (input capacitor, highand low-side MOSFETs, output capacitor, and inductor) must be short, wide, and low-resistance to minimize conversion losses and voltage overshoot/undershoot.

Segregate analog ground from power ground, joining at a single point—typically the IC’s ground paddle.

Supply lines and driver traces to MOSFET gates must be as short and wide as possible for proper timing and minimum noise.

Sensitive analog pins should be routed away from switching nodes (BST, LX), MOSFETs, and high-frequency power traces.

Alternative Models and Substitutes for the MAX1993ETG+

The selection of an alternative to MAX1993ETG+ depends on critical requirements such as dynamic output adjustment, current- and inductor-saturation protection, and package constraints. Some notable equivalents within Maxim/Analog Devices’ portfolio include:

MAX1540/MAX1541: Dual step-down PWM controllers with dynamic output selection, inductor saturation protection, and external reference input, analogous in protection and sequencing functionality.

MAX1992: Close sibling to the MAX1993ETG+; targeted for non-dynamic applications, but otherwise similar architecture and pinout (fixed and adjustable output support).

Other manufacturers’ controllers may match certain specifications (input range, DC accuracy) but may lack the unique dynamic voltage and on-the-fly protection features of the MAX1993ETG+. Careful review of application protection, transient, and dynamic voltage requirements should be conducted before substitution.

Conclusion

The MAX1993ETG+ is a specialized, highly adaptable step-down PWM controller designed to address the evolving needs of notebook, memory, and advanced embedded computing power delivery. With its Quick-PWM control engine, current and inductor protection, and dynamic voltage adjustment capabilities, it provides the foundation for efficient, scalable, and reliable power systems in space‑, efficiency-, and protection-critical applications. Product selection and integration engineers will find the MAX1993ETG+ to be a strategic fit for projects requiring both exceptional transient performance and fine-grained control of regulated rails in next-generation electronics.