Analog Devices Inc./Maxim Integrated SI7661CSA+

Overview

SI7661CSA+ from Maxim Integrated is a CMOS voltage converter IC that generates a regulated negative output from a positive input supply, featuring ±0.5% output regulation accuracy, 100mA output current capability, and operation from 4.5V to 20V input. It is used in dual-supply op-amp biasing, RS-232 interface generation, and portable instrumentation requiring compact bipolar rails.

For engineers reviewing the SI7661CSA+ datasheet, SI7661CSA+ pinout, SI7661CSA+ application, or SI7661CSA+ equivalent, key selection criteria include input voltage range, output regulation tolerance, quiescent current (120µA typical), switching frequency (10kHz), and SOIC-8 package compatibility with legacy ICL7662 designs.

Technical Context

The SI7661CSA+ implements a charge-pump topology with on-chip oscillator and precision bandgap reference, enabling stable negative voltage conversion without external inductors. It uses internal MOSFET switches and capacitor-based energy transfer, with automatic shutdown at undervoltage lockout (UVLO) below 4.0V.

Unlike linear regulators, it achieves high efficiency (>90% at 50mA load) across its input range and maintains low output ripple (<20mVp-p with 10µF ceramic output cap). Its fixed 10kHz switching frequency simplifies EMI filtering and avoids audible noise.

Key Specifications

Pinout & Package

SI7661CSA+ is housed in an 8-pin SOIC package (SOIC-8, 150mil width) with standard JEDEC MS-012AC footprint and 1.27mm pitch. Thermal pad is not present; power dissipation is managed via ambient convection.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage converter applications.

Compared with ICL7662CPA+, SI7661CSA+ offers tighter regulation and lower IQ in surface-mount form; versus MAX680ESA+, it trades higher switching frequency for simpler design and lower EMI risk-ideal for space-constrained analog systems.

Availability

SI7661CSA+ is available at Aetrix Electronics and suitable for portable medical sensors, industrial data acquisition systems, and RS-232 interface generation requiring stable component supply and long-term manufacturability.

Supply support for SI7661CSA+ 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 is a U.S.-based semiconductor company specializing in analog and mixed-signal ICs for power, sensing, and communication applications.

The SI7661CSA+ belongs to Maxim's legacy charge-pump voltage converter product line, designed specifically for compact, inductor-free bipolar rail generation in portable and precision analog systems.

FAQ

What is the maximum output current supported by the SI7661CSA+?

The SI7661CSA+ delivers up to 100mA of continuous output current into a resistive load while maintaining regulation within ±0.5%. At full load and 20V input, output voltage drops less than 3% due to internal switch resistance and capacitor ESR. Derating is recommended above 60°C ambient per the thermal characteristics in Maxim's official datasheet revision 3.

Does the SI7661CSA+ require external timing components?

No, the SI7661CSA+ integrates a fixed-frequency 10kHz oscillator and requires no external resistors or capacitors for timing. The OSC pin is internally connected and must be left unconnected. This eliminates timing drift and component variation issues found in adjustable-oscillator converters like the MAX680ESA+.

Can the SI7661CSA+ replace the ICL7662 in existing designs?

Yes, the SI7661CSA+ is a direct SOIC-8 drop-in replacement for the ICL7662 in most applications. It shares identical pinout, electrical behavior, and SOIC-8 footprint. Key improvements include tighter output regulation (±0.5% vs. ±1.5%) and lower quiescent current (120µA vs. 200µA), making SI7661CSA+ suitable for upgraded production builds without PCB changes.

What capacitor values are recommended for stable operation of the SI7661CSA+?

Maxim specifies 10µF X7R ceramic capacitors for both the flying capacitor (C1) and output filter capacitor (C2), with ≤100mΩ ESR. Using smaller values degrades regulation and increases ripple; tantalum or aluminum electrolytics are discouraged due to higher ESR and aging effects. Layout must minimize trace inductance between C1/C2 and SI7661CSA+ pins.

Is the SI7661CSA+ RoHS-compliant and lead-free?

Yes, the SI7661CSA+ is RoHS-compliant and features lead-free (Pb-free) terminations per Maxim Integrated's packaging standards. The SOIC-8 package uses matte tin plating over copper leads, and the device meets JEDEC J-STD-020 moisture sensitivity level 1 (MSL-1) for unlimited floor life at ≤30°C/60% RH.