ICL7126IPL+ - 3.5-Digit CMOS ADC | Maxim Integrated
MPN: ICL7126IPL+ ✓ ActiveICL7126IPL+ Overview
An ADC is an interface component that converts an analog voltage into a numeric value for measurement, control, or display. The ICL7126 integrates the active circuitry required for a complete 3.5-digit measurement channel on one CMOS IC. Unlike discrete meter designs, its integrated reference, clock, and conversion system reduce component count while retaining direct measurement of slowly changing voltages.
Key features include a true differential input and reference arrangement, a guaranteed zero reading for a zero-volt input, and true polarity at zero for precise null detection. The converter also provides approximately 1 pA typical input current. Its 3.5-digit architecture supports instrumentation displays and panel-meter applications where four digits of resolution are useful while a sign indicator improves readability around the zero point.
The CMOS implementation emphasizes low operating power, making the device suitable for portable instruments and battery-operated measurement panels. Integration of the reference and clock simplifies board design by reducing the number of external timing and calibration components. Differential measurement can also reject common-mode voltage when the source and reference paths are arranged carefully, although real-world accuracy still depends on input filtering, reference quality, grounding, and analog-layout discipline.
Typical uses include digital panel meters, laboratory measurement instruments, temperature and process monitoring, portable test equipment, and low-power sensor interfaces. The 40-pin PDIP package favors through-hole assembly, repairable prototypes, and larger industrial control boards where a surface-mount footprint would offer little practical benefit.
Designers should verify the complete electrical limits and recommended operating circuit in the manufacturer datasheet before release. Pay particular attention to input and reference polarity, conversion timing, bypass-capacitor placement, and the relationship between source impedance and accuracy. A stable, low-noise reference path and short analog traces are essential for repeatable measurements.
This product page combines the manufacturer product information with package-specific identification, application guidance, verified sourcing information, and drop-in replacement analysis. It also highlights the practical advantages and limitations of the 40-pin PDIP format for engineers deciding whether the ICL7126IPL+ fits an existing measurement-instrument design.
Drop-in alternatives for ICL7126IPL+ — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with ICL7126IPL+ (same form factor and footprint) — differing in Power Class.
ICL7126CPL+
✅ Drop-InContact for price
View Datasheet →TC7126IPL
✅ Drop-In📋 Reference alternative (not in catalog)
ICL7126IPL+ Maximum Ratings & Electrical Characteristics
| ADC Type | 3.5-digit successive-approximation A/D converter |
| Resolution | 0.05 percent |
| Architecture | CMOS monolithic analog-to-digital converter |
| Input Configuration | True differential input and reference |
| Typical Input Current | 1 pA |
| Zero-Input Reading | Guaranteed zero reading on all scales |
| Zero Polarity | True polarity at zero |
| Integrated Functions | Voltage reference and clock |
| Power Class | Very low power |
| Package | 40-pin PDIP |
| Terminal Count | 40 terminals |
| Mounting Type | Through-hole |
| Temperature Grade | Commercial |
| Operating Temperature | 0°C to 70°C |
| AEC-Q100 Qualification | Not applicable |
ICL7126IPL+ 40-pin pdip Pin Configuration Guide
Pin configuration for ICL7126IPL+ (40-pin pdip package). This analog component features input, output, and power supply pins. Refer to the manufacturer datasheet for offset null, compensation, and enable pin configurations. Ideal for signal conditioning and amplifier circuits.
No detailed pinout data available for ICL7126IPL+.
Refer to the datasheet for full pin configuration.
Typical Applications
ICL7126IPL+ is suitable for 6 applications: Digital Panel Meters, Portable Test Instruments, Industrial Process Monitoring, Temperature Measurement Front Ends, Laboratory Voltage Meters, Sensor Signal Conditioning.
Digital Panel Meters
The ICL7126IPL+ fits a digital panel meter because it integrates a 3.5-digit conversion channel, voltage reference, and clock into one CMOS device. Its 0.05-percent resolution provides adequate measurement detail for displaying pressure, level, position, temperature, and process variables. The true differential input arrangement can reject common-mode voltage when the signal and reference paths are balanced correctly. The 40-pin PDIP format also simplifies through-hole assembly and service replacement in larger meter platforms. For stable readings, keep analog traces short, use a clean reference, and confirm the required display interface and timing from the manufacturer data sheet.
Recommended
Portable Test Instruments
The ICL7126IPL+ supports portable test instruments where low power and component integration are important. The converter’s approximately 1 pA typical input current reduces loading of high-impedance sources, while its integrated reference and clock reduce the external circuitry needed for a working measurement channel. A 3.5-digit display can show a sign and four decimal digits, which is useful for handheld meters and field-service probes. Designers should still budget for display current, switch resistance, supply conversion loss, and the time required to acquire the signal before conversion.
Recommended
Industrial Process Monitoring
The ICL7126IPL+ is appropriate for industrial process monitoring when the required temperature range remains within its commercial 0°C-to-70°C rating. The differential input supports measurement of small signals riding on a controlled common-mode voltage, and the integrated reference and clock simplify the analog front end of a panel-mounted monitor. Its 40-pin through-hole package is especially convenient for repairable control cabinets and larger controller boards. For installations with extended temperature, vibration, electrical-noise, or long-life requirements, add appropriate protection and verify the availability of a suitably qualified product.
Recommended
Temperature Measurement Front Ends
The ICL7126IPL+ can serve as the measurement ADC in a temperature-monitoring front end when the sensor and signal path are compatible with a 3.5-digit dual-slope measurement architecture. The guaranteed zero reading on all scales improves display behavior around zero, while true polarity supports precise null or deviation measurements. A thermistor bridge, thermocouple interface, or RTD front end may require additional cold-junction, linearization, and protection circuits. Select external resistor and capacitor values from the application guidance and evaluate self-heating before assigning final measurement accuracy.
Recommended
Laboratory Voltage Meters
The ICL7126IPL+ is suitable for a laboratory voltage meter or bench instrument requiring a stable low-power reading with a signed 3.5-digit display. Its integrated clock and reference reduce assembly complexity, and the differential input architecture supports careful routing of sensitive measurement and reference signals. The commercial temperature range suits controlled indoor environments. The main design priorities are guarding against leakage, maintaining a low-noise reference, separating analog and digital return currents, and calibrating gain and offset. The 40-pin PDIP package remains practical for prototypes and medium-production through-hole assemblies.
Recommended
Sensor Signal Conditioning
The ICL7126IPL+ can evaluate low-level sensor outputs where the final result only needs approximately four displayed digits and the source can settle during the measurement interval. Its approximately 1 pA typical input current is valuable for high-impedance sources, while the integrated reference and clock reduce the number of sensitive external nodes. Place input filtering close to the device, avoid long leakage-prone traces, and confirm the source-impedance limits in the data sheet. For faster conversions, greater resolution, or simultaneous measurement of multiple channels, a redesigned ADC architecture may be more appropriate.
Recommended
Recommended Products Summary
Engineering reference data for ICL7126IPL+ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ICL7126CPL+ | TC7126IPL |
|---|---|---|---|
| Brand | Maxim Integrated | Maxim Integrated | Texas Instruments |
| Package | 40-pin PDIP | 40-pin PDIP | 40-pin PDIP |
| ADC Resolution | 3.5 digits, 0.05 percent | 3.5 digits, 0.05 percent | 3.5 digits |
| Converter Technology | CMOS successive-approximation ADC | CMOS 3.5-digit ADC | CMOS 3.5-digit ADC |
| Integrated Reference | Yes | Yes | Yes |
| Integrated Clock | Yes | Yes | Yes |
| Mounting Style | Through-hole | Through-hole | Through-hole |
Key Differentiators
- Exact-family 40-pin replacement path (vs ICL7126CPL+)
- Single-IC measurement channel (vs TC7126IPL)
- Low input loading (vs ICL7126CPL+)
- Signed 3.5-digit measurement (vs TC7126IPL)
Design Notes
Route the analog input and reference nets as short, quiet traces, and place their associated bypass capacitors close to the appropriate ICL7126IPL+ pins. Keep switching-regulator nodes, relay contacts, and high-current return paths away from the measurement section. A continuous ground plane can help, but analog and digital currents should return to their intended reference points without sharing narrow neck routes that create measurable voltage drops.
Because the typical input current is approximately 1 pA, even a modest source impedance or contaminated PCB surface can create an unwanted voltage contribution. Use a guarded or well-cleaned input area, avoid long leakage-prone traces, and select input filtering only after confirming its settling behavior during conversion. Verify source impedance, acquisition timing, and capacitor tolerances against the manufacturer data sheet before assigning practical measurement resolution.
Do not treat the 3.5-digit display resolution as the complete system accuracy. Offset, reference error, resistor tolerance, leakage, noise, and calibration drift can all reduce end-to-end accuracy. Establish gain and offset calibration limits for the finished instrument, and include reference stability, source settling, display loading, and switch resistance in the error budget. Use the complete manufacturer data sheet to distinguish converter resolution from total measurement uncertainty.
The 40-pin PDIP footprint supports straightforward through-hole routing, but analog and digital functions still need deliberate separation. Maintain a common ground reference without creating high-current loops between the converter, display, and external interface. Place input and reference components near their associated pins, avoid running the reference trace parallel to switching nodes, and review the complete pin-description table against the physical package orientation before fabrication.
Compliance Information
The commercial ICL7126IPL+ is not presented as an AEC-Q100-qualified automotive device. RoHS, REACH, lead-free, halogen-free, and conflict-minerals declarations were not identified and are recorded as unknown.