Analog Devices Inc./Maxim Integrated MAX853ISA+

Overview

MAX853ISA+ from Maxim Integrated is a low-noise, inverting, regulated charge-pump DC/DC converter designed to generate continuously adjustable negative bias voltages for GaAsFET power amplifiers in cellular handsets. It delivers up to 5mA output current at -0.5V to -9.0V with 1mV_p-p ripple, operates from 4.5V–10V input, and uses an external positive control voltage (V_CTRL) to set V_OUT.

For engineers reviewing the MAX853ISA+ datasheet, MAX853ISA+ pinout, MAX853ISA+ application, or MAX853ISA+ equivalent, key selection criteria include its externally controlled output voltage range, ultra-low 1mV_p-p output ripple under filtered V_CTRL, logic-level active-low shutdown (<1µA), 100kHz fixed switching frequency, and SO-8 package compatibility with GaAsFET biasing in RF front-end modules.

Technical Context

The MAX853ISA+ implements a two-stage architecture: a capacitive charge pump inverts the input voltage to produce 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 via a control voltage (CONT pin) referenced to a 1.28V internal bandgap, enabling precise V_OUT = –V_CTRL × (R2/R1) scaling.

Unlike the MAX850–MAX852 family members, the MAX853ISA+ replaces feedback (FB) with a dedicated CONT pin, eliminating resistor-divider dependency on OUT/GND and allowing independent control of V_OUT using any stable 0V–10V source - critical for dynamic bias tuning in adaptive RF power amplifiers.

Key Specifications

Pinout & Package

MAX853ISA+ 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 1 is marked by a beveled corner or dot.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX852ESA+, the MAX853ISA+ offers superior V_OUT flexibility and lower ripple but sacrifices clock synchronization. Against LM2776IDR, it provides higher output current and RF-optimized layout compatibility at the cost of higher integrated noise floor - making MAX853ISA+ the preferred choice for GaAsFET gate bias in cellular transmitter designs.

Availability

MAX853ISA+ is available at Aetrix Electronics and suitable for cellular handset RF front-ends, portable wireless data loggers, LCD contrast control systems, and personal communicator power management requiring stable component supply and long-term manufacturability.

Supply support for MAX853ISA+ 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 MAX850–MAX853 family was engineered specifically for low-noise, inverting charge-pump bias generation in GaAsFET-based RF power amplifiers - prioritizing ripple suppression, shutdown efficiency, and compact integration in space-constrained mobile handsets.

FAQ

What is the maximum output current capability of the MAX853ISA+?

The MAX853ISA+ delivers up to 5mA of continuous output current at its regulated negative output (OUT pin). This rating holds across the full -0.5V to -9.0V output range and over the specified operating temperature range of -25°C to +85°C. Performance is contingent on proper capacitor selection (1µF low-ESR for C1/C2/C3, 10µF for C4) and adequate PCB thermal management per the SO-8 package's 471mW dissipation limit at +70°C.

How does the MAX853ISA+ achieve its 1mV_p-p output ripple specification?

The MAX853ISA+ achieves <1mV_p-p output ripple through a two-stage architecture: first, a 100kHz charge pump generates an inverted rail at NEGOUT; second, an internal N-channel linear regulator filters and stabilizes this rail at OUT. Critical to meeting the 1mV_p-p spec is using a well-filtered, low-noise external control voltage (V_CTRL) applied to the CONT pin - unfiltered or noisy V_CTRL degrades ripple performance to the 2mV_p-p level typical of the MAX850–MAX852 variants.

Can the MAX853ISA+ be used with a 3.3V input supply?

No, the MAX853ISA+ cannot operate reliably with a 3.3V input supply. Its absolute minimum input voltage is 4.5V, as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. At inputs below 4.5V, regulation fails, output current drops significantly, and the internal charge pump cannot sustain the required voltage inversion headroom - especially critical when generating outputs more negative than -4.1V. For 3.3V systems, consider alternative charge pumps like the MAX1674 or LTC3260.

What is the function of the CONT pin on the MAX853ISA+?

The CONT pin on the MAX853ISA+ is the external control voltage input that directly sets the output voltage according to V_OUT = –V_CTRL × (R2/R1), where R1 and R2 form a resistor divider between OUT and CONT. Unlike the FB pin used in MAX850–MAX852, CONT accepts a 0V–10V analog voltage, enabling dynamic, processor-controlled adjustment of V_OUT without modifying feedback resistors - a key enabler for adaptive GaAsFET biasing in modern cellular transmitters.

Does the MAX853ISA+ require external capacitors, and what values are recommended?

Yes, the MAX853ISA+ requires four external capacitors: C1 and C2 (1µF, ≤0.8Ω ESR) as flying capacitors for charge-pump inversion; C3 (1µF, ≤0.8Ω ESR) as input bypass; and C4 (10µF, ≤0.2Ω ESR) as output bulk capacitance. All must be surface-mount chip tantalum or ceramic types. These values are validated in Maxim's Figure 2c application circuit and ensure stable operation, minimal dropout, and achievement of the <1mV_p-p ripple specification across temperature and load.