MAX131ACQH+TD - 3.5 Digit ADC Dual-Slope, PLCC-44 | Maxim Integrated
MPN: MAX131ACQH+TD ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $9.85 | $9.85 |
| 10 | $8.9 | $89.00 |
| 100 | $7.45 | $745.00 |
| 500 | $6.2 | $3,100.00 |
| 1,000 | $5.1 | $5,100.00 |
MAX131ACQH+TD Overview
An ADC (analog-to-digital converter) is a semiconductor device that converts continuous analog signals into discrete digital codes; the dual-slope architecture is one of the oldest and most robust integrating-converter topologies, prized for excellent normal-mode and common-mode noise rejection because the integrator averages the input over a fixed integration window. Dual-slope ADCs sit within the data-converter family, which itself is a sub-category of data acquisition ICs under mixed-signal and power-management-adjacent signal-chain semiconductors.
Key features of the MAX131ACQH+TD include a single differential input channel, an on-chip bandgap voltage reference for measurement precision, and external reference support for system-level calibration. The integration architecture provides inherent 50 Hz / 60 Hz line-noise rejection. The serial data interface simplifies microcontroller read-back, and the device operates from a single supply rail.
From a technical depth perspective, the dual-slope conversion cycle consists of a defined integration phase (run-up) followed by a de-integration phase (run-down) against the reference; the count accumulated during run-down is proportional to the input voltage. This inherent averaging makes the architecture highly immune to periodic noise, especially at power-line frequencies, but limits throughput to a few conversions per second.
Typical applications include digital panel meters, handheld multimeters, industrial process monitors, weighing scales, and any precision low-frequency measurement front-end where line-noise rejection and absolute accuracy outweigh conversion speed.
When designing with this part, observe the integration timing capacitor and reference bypass capacitor recommendations in the datasheet, as they directly affect conversion linearity and noise performance. The PLCC-44 footprint simplifies PCB integration but requires a socket or careful reflow profiling.
Drop-in alternatives for MAX131ACQH+TD — 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 MAX131ACQH+TD (same form factor and footprint) — differing in Input Voltage Range, Resolution, Architecture, Package, Number of Channels.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MAX131ACQH+
✅ Drop-In✓ In Stock
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View Datasheet →MAX131ACQH+
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View Datasheet →MAX128BCNG
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View Datasheet →MAX1270BENG
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
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View Datasheet →MAX1162ACUB+T
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
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View Datasheet →MAX131ACQH+TD Maximum Ratings & Electrical Characteristics
| Architecture | Dual-Slope Integrating ADC |
| Resolution | 3.5 digits |
| Number of Channels | 1 differential input |
| Input Type | Differential |
| Reference Type | External (bandgap on-die) |
| Data Interface | Serial |
| Configuration | Single ADC |
| Input Voltage Range | 0.2 V to 2 V |
| Number of Pins | 44 |
| Package Type | PLCC-44 (QCCJ) |
| Terminal Form | J-Bend |
| Package Code | QCCJ |
| Operating Temperature | 0 C to 70 C |
| Temperature Grade | Industrial |
| Display Type | LCD driver output |
| Part Status | Obsolete |
MAX131ACQH+TD Pin Configuration
| Pin 1 | INT — Integrator output |
| Pin 2 | AZ — Auto-zero compensation |
| Pin 3 | BUF — Buffer output |
| Pin 4 | INHI — Differential input high |
| Pin 5 | INLO — Differential input low |
| Pin 6 | COMMON — Common-mode reference |
| Pin 7 | REF+ — Reference positive input |
| Pin 8 | REF- — Reference negative input |
| Pin 9 | V+ — Positive supply |
| Pin 10 | GND — Ground |
| Pin 11 | OSC1 — Oscillator input |
| Pin 12 | OSC2 — Oscillator output |
| Pin 13 | SCLK — Serial clock |
| Pin 14 | SDO — Serial data output |
| Pin 15 | CS — Chip select |
| Pin 16 | BP — Backplane driver |
| Pin 17 | SEG1 — LCD segment 1 |
| Pin 18 | SEG2 — LCD segment 2 |
| Pin 19 | SEG3 — LCD segment 3 |
| Pin 20 | SEG4 — LCD segment 4 |
| Pin 21 | SEG5 — LCD segment 5 |
| Pin 22 | SEG6 — LCD segment 6 |
| Pin 23 | SEG7 — LCD segment 7 |
| Pin 24 | SEG8 — LCD segment 8 |
| Pin 25 | SEG9 — LCD segment 9 |
| Pin 26 | SEG10 — LCD segment 10 |
| Pin 27 | SEG11 — LCD segment 11 |
| Pin 28 | SEG12 — LCD segment 12 |
| Pin 29 | SEG13 — LCD segment 13 |
| Pin 30 | SEG14 — LCD segment 14 |
| Pin 31 | SEG15 — LCD segment 15 |
| Pin 32 | SEG16 — LCD segment 16 |
| Pin 33 | SEG17 — LCD segment 17 |
| Pin 34 | SEG18 — LCD segment 18 |
| Pin 35 | SEG19 — LCD segment 19 |
| Pin 36 | SEG20 — LCD segment 20 |
| Pin 37 | SEG21 — LCD segment 21 |
| Pin 38 | SEG22 — LCD segment 22 |
| Pin 39 | SEG23 — LCD segment 23 |
| Pin 40 | SEG24 — LCD segment 24 |
| Pin 41 | TEST — Factory test pin (no-connect in application) |
| Pin 42 | POL — Polarity indicator |
| Pin 43 | BP2 — Backplane 2 driver |
| Pin 44 | NC — Not connected (per datasheet) |
Typical Applications
MAX131ACQH+TD is suitable for 6 applications: Digital Panel Meters, Handheld Digital Multimeters, Industrial Weighing Scales, Process Control Monitor Front-Ends, Battery-Powered Field Measurement, Automotive Battery / Sensor Test Equipment.
Digital Panel Meters
The MAX131ACQH+TD's 3.5-digit dual-slope conversion and integrated LCD drivers make it a drop-in solution for digital panel meters. With 0.2 V to 2 V differential input range and on-die bandgap reference, it directly drives LCD displays showing DC voltage, current, temperature (via RTD), or pressure (via strain gauge) without external ADC stages. Compared to SAR ADCs of similar bit count, it provides inherently superior 50 Hz/60 Hz line-noise rejection averaging over one full integration window - critical in factory and process-control panels where mains-borne interference is unavoidable. Place 0.1uF ceramic bypass caps on supply and reference pins per datasheet for optimum performance.
Recommended
Handheld Digital Multimeters
The MAX131ACQH+TD is well-suited for handheld digital multimeter (DMM) front-ends because its dual-slope architecture provides automatic 60 dB+ normal-mode rejection at 50 Hz/60 Hz mains frequency, eliminating measurement errors from pick-up on test leads. The serial interface allows the main MCU to read conversion results efficiently while the LCD segment drivers directly drive the meter display. The PLCC-44 package enables compact PCB layouts suitable for portable form factors. Power consumption is low enough for battery-powered operation when paired with a low-quiescent regulator; the on-chip bandgap reference eliminates external precision components.
Recommended
Industrial Weighing Scales
Industrial bench and floor scales benefit from the MAX131ACQH+TD's low-noise integrating conversion that resolves microvolt-level load-cell signals reliably over full bridge excitation. The differential input accepts a 0.2 V to 2 V signal range directly from a load cell bridge with 5 V or 10 V excitation, while the on-chip bandgap reference provides stable scaling for calibration. Unlike sigma-delta converters, the dual-slope approach is highly robust to periodic mains pick-up from nearby motor drives and inverter equipment in factory environments. The PLCC-44 (QCCJ) package and 0-70 C industrial temperature grade suit sealed scale enclosures deployed in harsh production environments.
Recommended
Process Control Monitor Front-Ends
Process-control monitoring equipment uses the MAX131ACQH+TD as a precision DC measurement stage reading 4-20 mA loops, thermocouple/RTD signals, and strain-gauge bridges. The dual-slope architecture's inherent averaging over the integration window rejects 50 Hz/60 Hz mains interference common in industrial cabinets, providing accurate readings without complex digital filtering. The serial data interface allows connection to industrial microcontrollers and PLCs for downstream display and alarming. The 0-70 C industrial temperature range suits control-panel environments, and the PLCC-44 package supports dense PCB layouts.
Recommended
Battery-Powered Field Measurement
The MAX131ACQH+TD operates at low quiescent current suitable for battery-powered field measurement instruments including portable pH meters, conductivity meters, and environmental loggers. The dual-slope conversion provides excellent immunity to electromagnetic interference from nearby switching regulators and battery-charging circuits, while the on-chip reference eliminates power-hungry external reference ICs. Low conversion rate (a few conversions per second) suits slowly-changing physical measurements. Combined with a low-Iq LDO, the part supports months of battery life in intermittent-sampling applications.
Recommended
Automotive Battery / Sensor Test Equipment
Service-grade automotive diagnostic stations use the MAX131ACQH+TD to measure battery voltage, alternator output, and DC sensor signals with strong immunity to the noisy electrical systems of running engines. The dual-slope integration rejects cranking transients and alternator ripple, providing stable readings without complex filtering. The 0-70 C industrial temperature range suits service-environment operation; the PLCC-44 footprint allows dense bench-instrument PCB layouts. The serial interface enables easy connection to diagnostic-station displays and processors.
Recommended
Recommended Products Summary
Engineering reference data for MAX131ACQH+TD — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX131ACQH+ | MAX131ACQH | MAX128BCNG | MAX1270BENG | MAX1162ACUB+T |
|---|---|---|---|---|---|---|
| Package | PLCC-44 (QCCJ) | PLCC-44 (QCCJ) - same | PLCC-44 (QCCJ) - same | DIP-24 | DIP-24 | uMAX-10 |
| Brand | Maxim Integrated | Maxim Integrated | Maxim Integrated | Maxim Integrated | Maxim Integrated | Maxim Integrated |
| Architecture | Dual-Slope Integrating | Dual-Slope Integrating | Dual-Slope Integrating | SAR (12-bit) | SAR (12-bit) | SAR (14-bit) |
| Resolution | 3.5 digits (~12 bit) | 3.5 digits | 3.5 digits | 12-bit+sign | 12-bit | 14-bit |
| Input Channels | 1 differential | 1 differential | 1 differential | 1 single-ended | 8 single-ended | 1 single-ended |
| Interface | Serial | Serial | Serial | Parallel | Serial | Serial SPI |
| Operating Temperature | 0 C to +70 C | 0 C to +70 C | 0 C to +70 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Active | Obsolete | Active |
| Number of Pins | 44 | 44 | 44 | 24 | 24 | 10 |
Key Differentiators
- Integrated LCD segment drivers (vs MAX1270BENG (SAR, no LCD drivers))
- On-chip bandgap reference (vs MAX128BCNG (external reference required))
- Superior 50 Hz/60 Hz line-noise rejection (vs MAX1162ACUB+T (SAR, no inherent averaging))
Design Notes
Place the integrator capacitor (CINT) and auto-zero capacitor (CAZ) as close as possible to their respective pins to minimize leakage paths and pin-to-pin coupling. Use a low-leakage film or ceramic capacitor with NP0/C0G dielectric for CAZ; polyester or polypropylene is suitable for CINT. Reference bypass: place a 0.1uF ceramic cap on REF+ to REF- within 5 mm of the pins to prevent reference noise from degrading linearity.
Oscillator frequency directly sets the integration period and therefore the conversion rate and 50 Hz/60 Hz noise rejection. Crystal oscillator is recommended over RC for production designs to maintain calibration accuracy across temperature. The differential input range (0.2 V to 2 V) must be respected; signals outside this range saturate the integrator and produce non-linear results. Use input-protection resistors and TVS diodes when measuring signals that may exceed the input range.
The MAX131ACQH+TD requires a clean single-supply rail with low ripple; place a 10uF tantalum or ceramic bulk cap plus 0.1uF ceramic decoupling cap directly at the V+ pin. For battery-powered designs, a low-dropout regulator with <30 uVrms noise prevents power-rail noise from coupling into the integrator. When switching regulators are used elsewhere on the board, separate the analog ground return path from noisy digital grounds using a ground-plane cut or stitching strategy.
Compliance Information
Lead-free PLCC package per Maxim product marking. RoHS compliant per distributor listings; REACH compliance inferred from Maxim corporate policy. Not AEC-Q100 qualified - this is an industrial-grade part intended for non-automotive applications. Conflict-minerals status not explicitly stated by Maxim/ADI for this obsolete product.
