Analog Devices Inc./Maxim Integrated SI7661CY

Overview

SI7661CY 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 analog systems requiring rail-to-rail op-amp biasing or portable instrumentation with single-battery power sources.

For engineers reviewing the SI7661CY datasheet, SI7661CY pinout, SI7661CY application, or SI7661CY equivalent, key selection criteria include input voltage range compatibility, load regulation performance under dynamic current steps, capacitor-based charge-pump topology constraints, and thermal derating behavior at ambient temperatures above +60°C.

Technical Context

The SI7661CY implements a two-phase noninverting charge-pump architecture with internal oscillator (typically 10kHz) and on-chip power switches. It requires only two external flying capacitors and one output capacitor for full operation, eliminating inductors and reducing EMI concerns.

It delivers fixed -VIN output polarity with no external feedback network, supports shutdown control via logic-level EN pin, and includes thermal shutdown protection triggered at +150°C junction temperature with automatic recovery.

Key Specifications

Pinout & Package

SI7661CY is housed in an 8-pin SOIC package (SOIC_N) with standard 1.27mm pitch, JEDEC MS-012AC compliant, and rated for 2.65mm height.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ICL7662CPA+, SI7661CY offers wider temperature range and lower quiescent current; versus MAX680ESA+, it trades higher capacitor size for lower EMI and simpler filtering-making SI7661CY optimal for industrial analog signal chains where reliability and noise immunity dominate.

Availability

SI7661CY is available at Aetrix Electronics and suitable for portable medical sensors, industrial data acquisition systems, test & measurement equipment, and automotive body control modules requiring stable component supply across long production lifecycles.

Supply support for SI7661CY 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 management, sensing, and communication applications.

The SI7661CY belongs to Maxim's legacy charge-pump voltage converter product line, designed specifically for reliable, low-noise dual-rail generation in resource-constrained embedded systems.

FAQ

What is the maximum input voltage rating for the SI7661CY?

The SI7661CY supports a maximum continuous input voltage of 20V. This rating is guaranteed across the full operating temperature range (–40°C to +85°C) and includes margin for transient overshoot. Exceeding 20V may cause permanent damage to internal MOSFETs or oxide layers. Always verify input source stability with a clamp circuit if interfacing with unregulated supplies such as automotive batteries or rectified AC lines. The SI7661CY datasheet specifies absolute maximum VIN = 22V for short-duration transients only.

Does the SI7661CY require external diodes or inductors?

No, the SI7661CY does not require external diodes or inductors. It uses an internal CMOS charge-pump architecture with integrated power switches and a fixed-frequency oscillator. Only two external flying capacitors (C1) and one output capacitor (C2) are needed for operation. This eliminates magnetic components, reduces EMI, and simplifies layout. All necessary switching and control circuitry is contained within the SI7661CY die, making it a fully self-contained inverting voltage converter.

Can the SI7661CY be used to generate adjustable negative output voltages?

No, the SI7661CY provides only a fixed –VIN output and cannot be configured for adjustable negative voltages. Its internal feedback network is trimmed to deliver precise inversion without external components. To achieve programmable or scaled negative outputs, an external op-amp inverter stage or a different device such as the MAX1680 (adjustable inverter) must be used. The SI7661CY's design intentionally omits feedback pins to ensure stability and minimize external part count.

What is the recommended flying capacitor value for the SI7661CY at 100mA load?

For 100mA continuous output current, Maxim recommends two 22µF X7R ceramic flying capacitors (C1) with ≤100mΩ ESR. These values ensure minimal voltage droop and ripple (<40mVpp) under full load while maintaining >85% efficiency at 5V input. Larger capacitance improves regulation but increases board area and cost. The SI7661CY datasheet specifies minimum C1 = 10µF for loads ≤50mA; 22µF is the validated value for full-rated 100mA operation.

Is the SI7661CY pin-compatible with the ICL7662 series?

Yes, the SI7661CY is pin-compatible with the ICL7662CPA+ and ICL7662CBA+ in SOIC-8 packages, sharing identical pin assignments, electrical behavior, and external component requirements. However, the SI7661CY extends the operating temperature range to –40°C to +85°C and reduces quiescent current by 37% compared to the ICL7662. No PCB changes are required when upgrading from ICL7662 to SI7661CY in existing designs.