Analog Devices Inc./Maxim Integrated MAX765CSA+T

Overview

MAX765CSA+T from Maxim Integrated is a high-efficiency, current-limited PFM inverting DC-DC converter delivering -12V output at up to 250mA, with 120µA max supply current, 3V–16V input range, and internal P-channel MOSFET. It targets space-constrained, battery-powered systems requiring stable negative bias with ultra-low quiescent power.

For engineers reviewing the MAX765CSA+T datasheet, MAX765CSA+T pinout, MAX765CSA+T application, or MAX765CSA+T equivalent, key selection criteria include its fixed -12V output, 300kHz switching frequency enabling <5mm SMT magnetics, shutdown current <5µA, and compatibility with standard 47µH inductors and Schottky diodes like 1N5817.

Technical Context

The MAX765CSA+T employs a proprietary current-limited pulse-frequency modulation (PFM) control scheme that enforces a 16µs maximum on-time and 2.3µs minimum off-time, while dynamically scaling peak inductor current between 0.375A (light load) and 0.75A (heavy load). This enables >80% efficiency across 0.1–250mA loads without external compensation.

It operates as a self-biased inverting regulator: V+ and OUT form the total supply differential (≤20V), driving the internal P-MOSFET's gate with maximal voltage swing to minimize R_DS(ON). The 1.5V reference (REF) supports both fixed-output (FB tied to REF) and adjustable-output (external resistor divider) configurations.

Key Specifications

Pinout & Package

MAX765CSA+T is housed in an 8-pin SO (Small Outline) package, 150mil width, with GND on Pin 5, V+ shared on Pins 6 & 7, and LX on Pin 8 - matching the SO footprint of industry-standard 8-pin regulators.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar inverting DC-DC converter applications.

Compared with MAX775CSA+, MAX765CSA+T offers lower component count and quiescent current but less output power; versus TPS60403DBVR, it delivers triple the current, wider input range, and programmable shutdown - making it superior for industrial portable equipment.

Availability

MAX765CSA+T is available at Aetrix Electronics and suitable for LCD-bias generators, portable instrumentation, LAN adapters, and remote data-acquisition systems requiring stable component supply with guaranteed long-term availability.

Supply support for MAX765CSA+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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power-management ICs for industrial, communications, and consumer applications.

The MAX764/MAX765/MAX766 family was designed specifically for ultra-low-quiescent-current inverting DC-DC conversion in battery-powered and space-constrained systems - prioritizing efficiency across wide load ranges over high-speed transient response.

FAQ

What is the fixed output voltage of the MAX765CSA+T?

The MAX765CSA+T is factory-configured for a fixed -12V output with ±4% tolerance across temperature and load. This is achieved internally without external resistors - simply tie FB to REF for preset operation. The device also supports adjustable outputs from -1V to -16V using an external resistor divider connected to FB and REF, with R1 = 150kΩ and R2 calculated per VOUT = -1.5V × (1 + R2/R1).

Can the MAX765CSA+T operate from a 3.3V input supply?

Yes, the MAX765CSA+T supports input voltages from 3V to 16V, so 3.3V is within specification. However, at 3.3V input, the maximum achievable -12V output is constrained by the 20V V_IN–V_OUT differential limit - meaning VOUT cannot go below -16.7V, which is satisfied. Real-world output current will be reduced: at 3.3V input, max load is ~60mA (per MAX765C/E curve), sufficient for low-power LCD bias or sensor interfaces.

What is the shutdown current specification for MAX765CSA+T?

The MAX765CSA+T draws less than 5µA typical shutdown current when SHDN is pulled high (≥1.6V), with worst-case ≤10µA over temperature. This ultra-low shutdown current is confirmed in the Electrical Characteristics table and validated in the "Shutdown Current vs. Temperature" graph (Figure MAX764-07), where it remains under 3µA at +25°C and <8µA at +85°C - critical for long-term battery storage in portable instruments.

Which inductor value is recommended for MAX765CSA+T in fixed-output mode?

A 47µH surface-mount inductor is explicitly recommended for most MAX765CSA+T applications, as stated in the General Description and Design Procedure sections. This value balances size, efficiency, and ripple - supporting both continuous and discontinuous conduction modes. Inductors should have ≤100mΩ DC resistance, ≥0.75A saturation current rating, and ferrite or shielded construction (e.g., Coilcraft D03316-473 or Sumida CD75-470). Values between 22µH and 68µH are acceptable depending on load and ripple requirements.

Does MAX765CSA+T require an external Schottky diode, and if so, what specifications are critical?

Yes, MAX765CSA+T requires an external Schottky diode (e.g., 1N5817) connected between LX and VOUT. Critical specs include: 0.75A average forward current rating (matching peak switch current), low forward voltage (<0.45V at 0.75A) to minimize loss, and fast recovery (<100ns). At high temperatures or light loads, leakage may increase; in such cases, high-speed silicon diodes like MUR105 can be substituted - though efficiency drops ~3–5% due to higher V_F.