How to Choose the ICL7660ACPAZ or an Alternative: Charge-Pump Selection Guide

Bottom Line: Choose the ICL7660ACPAZ when a circuit needs a simple, low-current negative rail from a 1.5 V to 10 V positive supply and an 8-pin through-hole package suits the build. The three decisive checks are load current, allowable output error, and switching-noise tolerance. A nominal -5 V rail will not remain at -5 V under load because switch resistance, capacitor ESR, and charge-transfer losses create droop. For precision analog loads, calculate the worst-case rail at the required current and verify ripple; for higher current or quieter rails, use a higher-frequency charge pump, add post-regulation, or select an inductor-based converter instead.

The ICL7660ACPAZ is a CMOS switched-capacitor voltage converter commonly used to generate a negative rail for op-amps, sensor interfaces, LCD bias circuits, and low-power mixed-signal boards. Its attraction is architectural simplicity: a basic inverter needs the IC and two external capacitors, with no inductor and no magnetic field from an energy-storage coil.

That simplicity does not make every ICL7660-family device interchangeable. Input-voltage limits, oscillator behavior, package, temperature grade, capacitor choice, and load profile all affect whether a design works on the bench and remains reliable in production. This guide explains how to qualify the ICL7660ACPAZ, when to choose a close family member, and when to move to a different converter class.

1. Start With the Required Conversion Topology

The first selection decision is whether the circuit truly needs a low-power capacitive inverter rather than a regulated converter. In its standard configuration, the ICL7660ACPAZ inverts a positive input: approximately +5 V becomes an unloaded output close to -5 V. The device can also support voltage doubling, supply splitting, and cascaded multiplication, but every extra stage adds impedance, ripple, and loss.

A charge pump is a strong fit when the negative rail powers bias networks, small analog stages, or other loads measured in microamps to a few milliamps. It is also useful when board height, magnetic components, or electromagnetic coupling make an inductor unattractive. The two-capacitor inverter is easy to route and requires few procurement line items.

Do not select it merely because the unloaded output voltage looks correct. A charge pump is not a precision regulated -5 V source, and the output magnitude falls as current rises. If the load needs a guaranteed rail independent of input tolerance and current, include regulation in the architecture or choose a converter with feedback.

Define the rail requirement as a range rather than a nominal value. For example, an analog front end might operate from -3.8 V to -5.5 V while drawing 2 mA typical and 6 mA during a transient. That is a much better selection input than “need -5 V,” because it allows an engineer to budget converter droop, ripple, input tolerance, and startup behavior.

2. Check Input Voltage, Output Voltage, and Device Limits

The ICL7660ACPAZ is appropriate only when the complete input range stays inside its specified operating window and the resulting negative rail is safe for every connected load. The ICL7660A family is generally used from low-voltage supplies up to a 10 V input ceiling, while selected “S” variants extend the available family options. Always qualify the exact ordering code rather than transferring a limit from a similarly named part.

At light load, an inverter’s output approaches the negative of its input. A 5.0 V input can therefore produce a rail near -5.0 V, but a 4.5 V input cannot create a regulated -5.0 V rail without another conversion stage. Conversely, applying a high input may expose downstream analog pins to a negative voltage beyond their absolute maximum rating.

Low-voltage operation also requires attention to the LV pin. On classic ICL7660 implementations, LV is tied to ground for operation below the datasheet’s low-voltage threshold and left open at higher supply voltage. Treat that connection as a datasheet-controlled configuration item; a copied schematic with the wrong LV treatment can raise switch loss or violate the device recommendation.

Include tolerance and transients in the input check. A “9 V” source can be materially higher when unloaded, and automotive or industrial rails can have spikes that exceed the converter rating even when the nominal voltage seems acceptable. If the source is not already regulated, add clamp, filtering, or a pre-regulator as required by the system-level transient standard.

3. Calculate Load Current and Output Droop

Load current is usually the parameter that determines whether the ICL7660ACPAZ will meet the rail requirement. The converter behaves approximately like an ideal inverted source in series with an output resistance. A first-order estimate is:

VOUT ≈ -VIN + IOUT × ROUT

The sign convention aside, the practical result is that the negative output moves toward ground as current increases. Classic 7660-class devices can exhibit effective resistance of tens of ohms, with the exact value set by supply voltage, oscillator frequency, switch resistance, and external capacitors. At 10 mA, even 50 Ω of effective resistance creates about 0.5 V of droop before connector, trace, and transient effects are added.

Build a worst-case load budget. Add static load, bias resistors, indicator circuits, startup charging current, and any device whose current changes by operating mode. If several op-amps share the negative rail, use their maximum supply currents and include output-load effects rather than multiplying typical quiescent current.

The ICL7660ACPAZ is most comfortable where the average load is low and the circuit tolerates several hundred millivolts of rail movement. Loads around 1 mA are generally much easier than loads around 10 mA; tens of milliamps should trigger a careful datasheet calculation and usually an evaluation of a lower-impedance alternative. If a digital or RF load has sharp current pulses, average current alone is insufficient.

Prototype with the real load, not only a resistor. Measure the rail at minimum and maximum input voltage, at temperature extremes, and during load steps. If the minimum acceptable rail is -4.0 V, design for margin rather than accepting a room-temperature reading of -4.05 V.

4. Select Flying and Reservoir Capacitors

The flying capacitor and output reservoir capacitor directly control charge-transfer loss and ripple. A typical starting point for a 7660-class inverter is 10 µF for the flying capacitor and 10 µF for the output reservoir, followed by validation against the exact datasheet and load. Larger effective capacitance can reduce droop and ripple, but capacitor technology, bias derating, and ESR matter as much as the printed value.

The idealized capacitor ripple term is approximately:

ΔV ≈ IOUT / (fOSC × COUT)

At 5 kHz, 5 mA, and 10 µF, the ideal charge component is about 0.1 V per cycle. Real ripple is higher because the output capacitor has ESR and the switching current arrives in pulses. A 1 Ω ESR contribution at a 5 mA pulse scale adds millivolts, but peak current and layout can make the observed edge larger.

Ceramic capacitors offer low ESR but can lose 40% to 80% of their nominal capacitance under DC bias, depending on case size, dielectric, and voltage rating. Aluminum electrolytics retain capacitance more predictably but have higher ESR and poorer low-temperature behavior. Tantalum devices need surge and reverse-voltage discipline. Select by effective capacitance at the operating voltage and temperature, not by the catalog headline.

Place the flying capacitor close to CAP+ and CAP- and keep the switching loop compact. Place the reservoir capacitor close to VOUT and ground. A long shared ground path can inject pump current into an op-amp reference, creating an apparent converter-noise problem that is actually a layout problem.

5. Evaluate Oscillator Frequency, Ripple, and Sensitive Loads

Switching frequency determines capacitor size, output impedance, audible-risk interactions, and the spectral location of converter noise. Standard 7660-class devices switch in the low-kilohertz region, where harmonics can enter audio or precision measurement bandwidths. Some related variants offer a frequency-boost function or a higher nominal oscillator, moving the fundamental above much of the audible band.

Higher frequency is not automatically quieter. It reduces the charge required per cycle for a given load and can lower ripple with the same capacitors, but it increases switching edges and may raise radiated or conducted energy at higher harmonics. A sensitive ADC, photodiode amplifier, or audio preamplifier may require an RC or LC post-filter, a low-noise linear post-regulator, careful grounding, or converter synchronization.

Measure both time-domain ripple and frequency-domain spurs. An oscilloscope with a short ground spring reveals switching edges that a long probe lead can exaggerate. An FFT or spectrum analyzer helps identify whether the pump fundamental aliases into the signal band.

For audio, compare the converter frequency with sample rates, modulation frequencies, and gain-bandwidth behavior. For ADC systems, test representative conversion sequences because a quiet idle waveform can become noisy when the analog front end changes load. If the rail must be spectrally clean, a converter selected solely by DC efficiency is incomplete engineering.

6. Verify Startup, Shutdown, and Fault Behavior

A suitable converter must behave correctly during power sequencing, not only in steady state. At startup, the flying and reservoir capacitors initially look discharged, so the device must transfer enough charge before the negative rail reaches its operating value. The load may begin drawing current before that happens, extending startup or holding the rail near ground.

Check how the powered circuit behaves while VOUT ramps through intermediate voltages. An op-amp can saturate, an analog switch can conduct unexpectedly, or an ADC input protection structure can carry current if another rail is already present. If sequencing matters, add enable control elsewhere, gate the load, or hold the system in reset until the negative rail is valid.

Shutdown also deserves analysis because the output capacitor stores a negative charge. A circuit can remain partially powered after VIN disappears, especially when signal pins are driven from another domain. Add a discharge path when a predictable decay time is required, but include its continuous current in the normal load budget.

Fault review should cover shorted output, reversed or incorrectly polarized capacitors, open capacitors, and input overvoltage. The ICL7660ACPAZ should not be treated as a protected negative-rail module; the surrounding design must implement any protection required by the product safety and reliability plan.

7. Match Package, Temperature Grade, and Procurement Needs

The ordering code must match the assembly process, temperature range, lifecycle plan, and approved-manufacturer list. The ICL7660ACPAZ is attractive for through-hole prototypes, repairable industrial assemblies, and low-volume products that use an 8-pin DIP footprint. A surface-mount board may be better served by a compatible family member in SOIC or a compact package.

Do not infer temperature grade from the base name alone. Commercial and industrial ordering codes can share the same electrical function while carrying different tested temperature ranges. Record the complete MPN in the BOM and approved vendor list, including suffixes associated with package and environmental compliance.

Procurement qualification should include date code, moisture-sensitivity requirements for surface-mount variants, package marking, and traceability. FindMyChip connects buyers with more than 200 verified distributors and applies a five-point authentication process; it complements authorized-channel sourcing when teams need cross-market availability or competitive China pricing.

For production, verify current lifecycle status and request lot-level documentation. Use the component search to compare available ordering codes, then submit an RFQ when package, quantity, date-code, or traceability requirements are firm. FindMyChip targets a response within 24 hours, which is useful when the approved BOM permits multiple qualified variants.

Recommended Product Comparison

The table below compares database-listed family options for initial engineering review. Voltage, frequency, temperature, and package details must be confirmed in the current manufacturer datasheet for the exact suffix. Price ranges are non-binding prototype planning allowances, not live quotations; volume price depends on quantity, date code, package, and traceability.

Product	Input / topology	Package or grade cue	Key selection point	Planning price range	Best for
ICL7660ACPAZ	1.5-10 V-class inverter	Through-hole DIP, commercial-grade family	Simple two-capacitor negative rail and easy prototyping	US$1-3 each	Through-hole prototypes and serviceable low-current analog boards
ICL7660ACBAZA	1.5-10 V-class inverter	Surface-mount family option	Similar core function in a production-oriented footprint	US$1-3 each	Compact surface-mount designs
ICL7660AIBAZA	1.5-10 V-class inverter	Industrial-grade family cue	Wider qualified temperature use than commercial ordering codes	US$2-5 each	Industrial instrumentation with temperature requirements
ICL7660CPAZ	Classic 7660 inverter	Through-hole DIP	Legacy-compatible ordering code; verify performance differences from “A” version	US$1-3 each	Existing DIP layouts and maintenance BOMs
ICL7660SCBAZ	“S” family inverter	Surface-mount family option	Consider when the S-version input or oscillator features match the design	US$2-5 each	Designs needing features not offered by the base A variant

These five MPNs should not be substituted solely because their pin counts look similar. Confirm pin function, maximum supply, LV behavior, oscillator options, capacitor recommendations, and temperature grade. If the approved BOM can accept multiple parts, document the conditions under which each substitution is valid.

Selection Decision Flowchart

Use the following decision sequence to determine whether the ICL7660ACPAZ is the right converter.

If the circuit needs a negative rail from a positive supply, continue; otherwise, choose a topology designed for the required positive, boosted, or regulated output.
If the full input range is inside the exact ICL7660ACPAZ operating limits, continue; otherwise, select a rated alternative or add a pre-regulator.
If the average and peak load produce an acceptable worst-case VOUT after calculated output resistance and ripple, continue; otherwise, select a lower-impedance or inductor-based converter.
If low-kilohertz switching energy is acceptable in the signal band, continue; otherwise, evaluate a boosted-frequency family member, filtering, post-regulation, or a low-noise topology.
If an 8-pin through-hole package matches the PCB and assembly process, continue with ICL7660ACPAZ; otherwise, qualify a surface-mount candidate.
If startup, shutdown, and residual negative charge are safe for the load, finalize the design; otherwise, add sequencing, load isolation, or a discharge network.
If sourcing requirements are satisfied by the exact suffix and traceable stock, release the BOM; otherwise, qualify an alternate before production.

This flow prevents a common mistake: choosing by nominal voltage alone. The correct decision uses electrical margin, noise behavior, mechanical fit, and supply-chain control together.

Practical Design and Validation Checklist

Before schematic release, record VIN minimum, nominal, maximum, and transient maximum. Record load current in every mode, including startup and fault cases. Calculate output droop with a conservative effective resistance and calculate the ideal ripple term with the minimum effective output capacitance.

Choose capacitor voltage ratings with margin across both terminals. Verify effective capacitance under DC bias, tolerance, and temperature. Check polarity carefully if using electrolytic or tantalum capacitors; the negative output node makes intuitive placement errors easy.

During PCB layout, minimize the CAP+ to flying-capacitor to CAP- loop. Return the reservoir capacitor directly to the converter ground region, then connect that region to the analog ground strategy at a controlled point. Keep high-impedance sensor traces away from the pump loop.

On prototypes, measure VOUT at no load, nominal load, and maximum load. Repeat at minimum and maximum VIN. Capture startup, shutdown, and load-step waveforms, then inspect ripple with bandwidth appropriate to the application.

For production validation, test temperature corners and multiple component lots. A capacitor substitution can change effective capacitance or ESR enough to alter ripple, even when the BOM value remains “10 µF.” Lock critical capacitor characteristics in the purchasing specification rather than allowing unrestricted value-only substitution.

FAQ

Is the ICL7660ACPAZ a regulated -5 V converter?

No. The ICL7660ACPAZ is a switched-capacitor voltage inverter whose unloaded output approaches the negative of the input voltage. Its output moves toward ground as load current, switch resistance, capacitor ESR, and charge-transfer loss increase. If a circuit requires an accurate -5 V rail, budget the droop and add regulation or choose a feedback-controlled converter.

How much current can an ICL7660ACPAZ supply?

The usable current depends on the minimum acceptable output voltage, input voltage, capacitors, temperature, and ripple limit. Treat it as a low-current source: applications at a few milliamps are easier to design than loads at tens of milliamps. Calculate VOUT from worst-case effective resistance and validate with the actual pulsed or static load.

What capacitor values should I use with the ICL7660ACPAZ?

Ten-microfarad flying and reservoir capacitors are a common starting point for classic 7660 circuits, but the exact datasheet recommendation controls. Select effective capacitance after tolerance, temperature, and ceramic DC-bias derating. Low ESR reduces step ripple, while compact placement reduces switching-loop inductance and noise coupling.

Can I replace the ICL7660ACPAZ with any ICL7660 device?

No. Related devices can differ in maximum input voltage, oscillator or boost behavior, LV-pin guidance, tested temperature range, and package. Compare the exact ordering-code datasheets and verify the PCB footprint. A safe alternate must satisfy electrical limits, noise requirements, assembly constraints, and traceability rules simultaneously.

When should I avoid a charge-pump inverter?

Avoid a basic charge pump when the load needs high current, tight regulation, very low broadband noise, or large conversion ratios. An inductor-based inverting converter generally provides better current capability and regulation. A higher-frequency charge pump can still be useful for moderate loads, while post-filtering or linear post-regulation can improve a low-current analog rail.

Conclusion

The ICL7660ACPAZ is a practical choice when the design needs a low-current negative rail, accepts load-dependent droop, and benefits from an inductor-free 8-pin DIP solution. Its success depends less on the nominal “+5 V to -5 V” function than on a disciplined check of load current, capacitor behavior, switching noise, sequencing, and the complete ordering code.

Start by defining a permitted rail range and worst-case current. Then calculate droop and ripple, validate the actual load, and compare package or temperature variants only after confirming their exact datasheets. For parts availability, use FindMyChip to search the ICL7660 family, or request a quote with package, quantity, date-code, and documentation requirements for a response from verified distributors.