Analog Devices Inc./Maxim Integrated MAX850ESA+T

Overview

MAX850ESA+T from Maxim Integrated is a low-noise, inverting, regulated charge-pump DC-DC converter designed specifically for GaAsFET biasing in cellular transmitter amplifiers. It delivers a fixed -4.1V output at up to 5mA, operates from 4.5V to 10V input, achieves 2mV_p-p output ripple via integrated linear regulation, and features logic-level shutdown with <1µA max current over temperature.

For engineers reviewing the MAX850ESA+T datasheet, MAX850ESA+T pinout, MAX850ESA+T application, or MAX850ESA+T equivalent, key selection criteria include fixed negative output stability, ultra-low noise performance under RF-sensitive bias conditions, SO-8 package compatibility with handheld RF layout constraints, and GaAsFET gate-voltage regulation accuracy across temperature and input variation.

Technical Context

The MAX850ESA+T implements a two-stage architecture: a capacitive charge pump inverts the input voltage to generate an unregulated negative rail at NEGOUT, followed by an internal N-channel linear regulator that stabilizes and filters the output at OUT. Regulation is achieved using a precision -1.28V internal reference applied to the FB pin, which is grounded to set the fixed -4.1V output.

Its 100kHz fixed switching frequency minimizes EMI in RF front-end circuits, while the integrated linear post-regulator provides >60dB AC rejection of supply noise and reduces charge-pump ripple to 2mV_p-p - critical for maintaining GaAsFET transconductance linearity and amplifier gain flatness in 900MHz/1.8GHz bands.

Key Specifications

Pinout & Package

MAX850ESA+T is housed in an 8-pin SO (Small Outline) package, 3.9mm × 4.9mm body size, 1.27mm pitch, with exposed pad not connected. Pin functions are validated per Maxim's MAX850 datasheet Rev 2 (19-0238) and confirmed on official ordering information tables.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar negative charge-pump regulator applications.

Compared with MAX851ESA+T, MAX850ESA+T offers direct active-low GPIO compatibility; compared with LM2776IDRGT, it delivers 12× lower output ripple essential for RF linearity - making MAX850ESA+T the only option meeting GaAsFET bias noise specifications in cellular PA designs.

Availability

MAX850ESA+T is available at Aetrix Electronics and suitable for cellular telephone transmitter amplifiers, LCD contrast control circuits, and wireless data loggers requiring stable component supply with guaranteed long-term manufacturability.

Supply support for MAX850ESA+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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power-management ICs for industrial, communications, and consumer applications.

The MAX850–MAX853 family was engineered specifically for low-noise GaAsFET biasing in portable RF transmitters, prioritizing ripple suppression, shutdown efficiency, and integration to replace discrete charge-pump + LDO solutions.

FAQ

What is the output voltage tolerance of the MAX850ESA+T under full load and temperature range?

The MAX850ESA+T delivers a nominal -4.1V output with ±2% tolerance across its full operating temperature range (-40°C to +85°C) and at 5mA load. This specification is verified per Maxim's Electrical Characteristics table (Rev 2, page 2), where V_OUT min/max are listed as -4.2V and -3.9V respectively, ensuring consistent GaAsFET gate bias regardless of ambient or battery voltage drift.

Can the MAX850ESA+T be used with a 3.3V input supply?

No - the MAX850ESA+T requires a minimum 4.5V input voltage to maintain regulation and deliver its rated -4.1V output at 5mA. At inputs below 4.5V, the device may start but cannot sustain proper charge-pump operation or linear regulation; output voltage collapses and ripple increases significantly. This limitation is explicitly stated in the Absolute Maximum Ratings and Electrical Characteristics sections of the MAX850ESA+T datasheet.

Does the MAX850ESA+T require external compensation components for stability?

No, the MAX850ESA+T does not require external compensation. Its internal linear regulator is factory-compensated for use with the specified 10µF output capacitor (C4). Stability is guaranteed when using low-ESR ceramic or tantalum capacitors as outlined in the Applications Information section - adding extra RC networks or compensation capacitors may degrade transient response or cause oscillation.

How does the MAX850ESA+T achieve 2mV_p-p output ripple when typical charge pumps exhibit >20mV ripple?

The MAX850ESA+T achieves 2mV_p-p output ripple through cascaded architecture: first, a 100kHz charge pump generates an inverted rail at NEGOUT; second, an internal N-channel linear regulator with high PSRR (>60dB) filters switching artifacts before delivering the final output at OUT. This two-stage design - unlike single-stage charge pumps - actively suppresses both fundamental and harmonic ripple, as confirmed in Figure 4 (MAX850–MAX852 Output Noise and Ripple) of the MAX850ESA+T datasheet.

Is the MAX850ESA+T pin-compatible with the MAX852ESA+T?

No - the MAX850ESA+T is not pin-compatible with the MAX852ESA+T. While both share the same SO-8 package and pin 1–8 physical layout, pin 4 is SHDN on MAX850ESA+T but OSC (external clock input) on MAX852ESA+T. Interchanging them would result in non-functional shutdown control or unintended oscillator gating, causing failure to regulate or erratic startup behavior.