Analog Devices Inc./Maxim Integrated MAX756CSA

Overview

MAX756CSA from Maxim Integrated is a CMOS step-up DC-DC switching regulator optimized for low-input-voltage, battery-powered systems. It accepts input as low as 0.7V and delivers pin-selectable 3.3V or 5V output at up to 300mA (5V mode) or 200mA (3.3V mode), with 87% typical full-load efficiency and 60µA quiescent current - enabling long runtime in palmtop computers and glucose meters.

For engineers reviewing the MAX756CSA datasheet, MAX756CSA pinout, MAX756CSA application, or MAX756CSA equivalent, this page provides verified technical context, validated pin functions, confirmed operating parameters, and real-world design constraints including startup voltage vs. load, shutdown leakage, reference regulation accuracy, and LBO open-drain behavior under low-battery conditions.

Technical Context

The MAX756CSA implements a constant-off-time pulse-frequency modulation (PFM) control scheme with no external oscillator, enabling variable switching frequency up to 500kHz. Its internal 1A/0.5Ω N-channel MOSFET switch operates with self-oscillating inductor current between fixed peak and valley limits, delivering high efficiency across wide load ranges while maintaining ultra-low quiescent current.

It integrates a precision 1.25V reference (±1.5% over temperature), active low-battery detection (LBI threshold = 1.25V, hysteresis = 25mV), and bootstrapped operation powered from the OUT pin - allowing sustained regulation even when input sags below 1V after startup. Shutdown mode retains reference and LBI comparator functionality while drawing only 20µA.

Key Specifications

Pinout & Package

MAX756CSA is housed in an 8-pin SO (Small Outline) package per JEDEC MS-012, 3.9mm × 4.9mm body, 1.27mm pitch, with GND pin (7) requiring direct soldering to PCB ground plane for optimal thermal and noise performance.

Key Features

Applications

Availability

MAX756CSA is available at Aetrix Electronics and suitable for portable medical instrumentation, handheld computing, battery-powered data collection, and personal communication devices requiring stable component supply with guaranteed industrial temperature range support.

Supply support for MAX756CSA 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 demanding industrial, medical, and portable applications.

The MAX756 product line delivers highly integrated, low-voltage step-up DC-DC converters targeting space-constrained, battery-operated systems where startup voltage, quiescent current, and integrated monitoring are critical.

FAQ

What is the minimum input voltage required for MAX756CSA to start up?

The MAX756CSA requires a minimum input voltage of 0.7V to initiate startup under typical conditions. This value is confirmed in the Electrical Characteristics table and supported by Figure 1's "Minimum Start-Up Supply Voltage vs. Load Current" plot. Once started, the MAX756CSA can sustain regulation with input as low as 0.7V - a key enabler for single-cell alkaline or NiMH applications. The actual startup voltage increases slightly with higher load currents, reaching ~1.1V at 200mA.

Can MAX756CSA operate in shutdown mode while retaining low-battery monitoring capability?

Yes, the MAX756CSA maintains full low-battery detection functionality in shutdown mode. When SHDN is pulled low, the SMPS is disabled, but the internal 1.25V reference and LBI comparator remain active, and LBO continues to sink current when LBI falls below threshold. Shutdown quiescent current is specified at 20µA - measured at VIN - confirming active monitoring without significant battery drain. This behavior is explicitly documented in the Features list and Pin Description section.

What is the purpose of the 3/5 pin on MAX756CSA, and how should it be configured?

Pin 2 (3/5) on the MAX756CSA selects the regulated output voltage: logic LOW sets 5V output, logic HIGH sets 3.3V output. It is an internally pulled-up input, so tying it to GND selects 5V mode, while connecting it to OUT (or a logic HIGH signal) selects 3.3V mode. This pin must never be left floating. The selection is static - no dynamic reconfiguration during operation - and determines both output voltage and internal biasing for optimal efficiency in each mode, as shown in the Typical Operating Characteristics efficiency curves.

Does MAX756CSA require an external feedback resistor network like adjustable regulators?

No, the MAX756CSA does not require external feedback resistors. Unlike the MAX757 (which uses FB and REF pins for adjustable output), the MAX756CSA has fixed 3.3V/5V outputs selected solely by the 3/5 pin state. Its internal feedback loop is fully integrated, eliminating external resistor networks and associated tolerance errors. This simplifies layout, reduces BOM count, and improves reliability - a key differentiator confirmed in the General Description and Pin Configuration diagrams.

What package type and thermal characteristics apply to MAX756CSA?

The MAX756CSA is supplied in an 8-pin SO (Small Outline) package per JEDEC MS-012, with dimensions 3.9mm × 4.9mm and 1.27mm lead pitch. Its continuous power dissipation at TA = +70°C is rated at 471mW, with derating of 5.88mW/°C above that temperature. Thermal performance depends critically on GND pin (7) being soldered directly to a PCB ground plane - a requirement emphasized in the PC Layout and Grounding section to minimize thermal resistance and ground bounce.