MAX131ACQH+ - 3.5 Digit ADC w/ Bandgap Reference | Maxim Integrated
MPN: MAX131ACQH+ ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $14.5 | $14.50 |
| 10 | $13.05 | $130.50 |
| 100 | $11.6 | $1,160.00 |
| 500 | $10.44 | $5,220.00 |
| 1,000 | $9.28 | $9,280.00 |
MAX131ACQH+ Overview
An ADC (analog-to-digital converter) with integrated LCD driver is a mixed-signal IC that converts an analog input voltage to a numeric BCD/7-segment output suitable for direct multiplex to an LCD. The dual-slope architecture provides excellent rejection of 50 Hz/60 Hz line-frequency noise (a critical parameter for panel-meter accuracy), and the integrated bandgap reference eliminates the need for an external precision reference, simplifying the BOM.
Key features include a single +5 V supply operation, input voltage range of 0.2 V to 2.0 V (differential), ±2000-count conversion range (3.5 digits), on-chip bandgap reference with low temperature drift, on-chip LCD backplane/segment drivers, and an integrated oscillator. The 44-pin PLCC (QCCJ) package with J-bend terminal form provides a low-profile surface-mount option for industrial and commercial panel-meter designs.
The MAX131ACQH+ uses a dual-slope (integrating) conversion architecture, which inherently averages out 50 Hz/60 Hz power-line interference over the integration period. The bandgap reference is laser-trimmed for low drift across the commercial 0 C to +70 C temperature range, allowing direct-reading accuracy without external calibration adjustments.
Typical applications include digital panel meters (DPMs), handheld DVMs, weighing scales, process monitor readouts, and battery-powered LCD instrumentation. The integrated LCD driver directly multiplexes to a 3.5-digit 7-segment display, eliminating external display-driver ICs.
When designing with this device, the input signal must be conditioned to within the 0.2 V to 2.0 V differential input range using an external input attenuator or op-amp front-end. Decoupling capacitors (typically 0.1 uF) must be placed close to the supply and reference pins. The integrating architecture requires CINT and CAZ external capacitors; their selection dictates conversion speed vs noise rejection trade-off.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet, enabling faster part selection and PCB reuse for legacy panel-meter designs.
Drop-in alternatives for MAX131ACQH+ — 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+ (same form factor and footprint) — differing in Resolution, Terminal Form, Operating Temperature, Package, Temperature Grade.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MAX131ACQH+TD
✅ Drop-In✓ In Stock
$5.1 / Unit
View Datasheet →MAX131AEQH+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX131C/D
✅ Drop-In📋 Reference alternative (not in catalog)
MAX131ACQH+ Maximum Ratings & Electrical Characteristics
| Number of Channels | 1 |
| Architecture | Dual-Slope Integrating |
| Resolution | 3.5 digits |
| Input Voltage Range | 0.2 V to 2.0 V (differential) |
| Conversion Range | ±2000 counts |
| Display Output | LCD (on-chip driver) |
| Reference Type | Internal bandgap |
| Supply Voltage | 5 V (typical) |
| Package | PLCC-44 (QCCJ) |
| Mounting Type | Surface Mount |
| Terminal Form | J-Bend |
| Package Code | QCCJ |
| Temperature Grade | Commercial |
| Operating Temperature | 0 C to +70 C |
| Lead Free | Yes |
| Screening Level | Commercial |
MAX131ACQH+ Pin Configuration
| Pin 1 | V+ — Positive supply voltage |
| Pin 2 | D1 — LCD segment driver D1 |
| Pin 3 | C1 — LCD segment driver C1 |
| Pin 4 | BP — LCD backplane |
| Pin 5 | G1 — LCD segment driver G1 |
| Pin 6 | E1 — LCD segment driver E1 |
| Pin 7 | D2 — LCD segment driver D2 |
| Pin 8 | C2 — LCD segment driver C2 |
| Pin 9 | G2 — LCD segment driver G2 |
| Pin 10 | E2 — LCD segment driver E2 |
| Pin 11 | D3 — LCD segment driver D3 |
| Pin 12 | C3 — LCD segment driver C3 |
| Pin 13 | GND — Ground |
| Pin 14 | TEST — Test pin (factory use) |
| Pin 15 | INT — Integrator output |
| Pin 16 | CINT — Integrator capacitor |
| Pin 17 | CAZ — Auto-zero capacitor |
| Pin 18 | IN- — Differential input negative |
| Pin 19 | IN+ — Differential input positive |
| Pin 20 | VREF — Reference voltage |
| Pin 21 | BUFF — Buffer output |
| Pin 22 | OSC1 — Oscillator input |
| Pin 23 | OSC2 — Oscillator output |
| Pin 24 | A1 — LCD segment driver A1 |
| Pin 25 | F1 — LCD segment driver F1 |
| Pin 26 | B1 — LCD segment driver B1 |
| Pin 27 | A2 — LCD segment driver A2 |
| Pin 28 | F2 — LCD segment driver F2 |
| Pin 29 | B2 — LCD segment driver B2 |
| Pin 30 | A3 — LCD segment driver A3 |
| Pin 31 | F3 — LCD segment driver F3 |
| Pin 32 | B3 — LCD segment driver B3 |
| Pin 33 | POL — Polarity indicator |
| Pin 34 | DP — Decimal point |
| Pin 35 | G3 — LCD segment driver G3 |
| Pin 36 | E3 — LCD segment driver E3 |
| Pin 37 | D4 — LCD segment driver D4 |
| Pin 38 | C4 — LCD segment driver C4 |
| Pin 39 | G4 — LCD segment driver G4 |
| Pin 40 | E4 — LCD segment driver E4 |
| Pin 41 | BP2 — LCD backplane 2 |
| Pin 42 | NC — Not connected (per datasheet) |
| Pin 43 | NC — Not connected (per datasheet) |
| Pin 44 | BP3 — LCD backplane 3 |
Typical Applications
MAX131ACQH+ is suitable for 6 applications: Digital Panel Meters (DPMs), Handheld Digital Voltmeters (DVMs), Electronic Weighing Scales, Process Monitor Readouts, Battery-Powered LCD Instrumentation, Educational and Hobbyist Electronics Projects.
Digital Panel Meters (DPMs)
The MAX131ACQH+ integrates the ADC, bandgap reference, clock, and LCD driver in a single 44-pin PLCC IC, which is the ideal BOM-reducing solution for digital panel meters displaying voltage, current, temperature, or pressure. The dual-slope architecture inherently averages out 50 Hz/60 Hz line noise over the integration period, achieving ±0.1% accuracy without digital filtering. With 3.5-digit (2000-count) resolution and a 0.2 V to 2.0 V differential input range, the MAX131ACQH+ directly drives a multiplexed 3.5-digit 7-segment LCD via its on-chip backplane and segment drivers, eliminating external display-driver ICs.
Recommended
Handheld Digital Voltmeters (DVMs)
Battery-powered handheld DVMs benefit from the MAX131ACQH+'s low-power operation and integrated LCD driver, which removes the need for separate display-driver and reference ICs. The on-chip bandgap reference provides a stable full-scale voltage that drifts less than 50 ppm/C across the commercial 0 C to +70 C range, supporting direct-reading accuracy on a 3.5-digit display. Designers pair the MAX131ACQH+ with an input attenuator/divider and an op-amp front-end to extend measurement range from millivolts up to 600 V, enabling a compact 4-range handheld meter in a single PCB design.
Recommended
Electronic Weighing Scales
Load-cell-based weighing scales demand high noise rejection at line frequency because the bridge excitation and signal conditioning pick up mains-frequency interference; the MAX131ACQH+ solves this with its dual-slope integrator that averages out 50 Hz and 60 Hz over each conversion cycle. The internal bandgap reference stabilizes the ADC full scale against supply and temperature variation, while the integrated LCD driver directly multiplexes a 3.5-digit weight display without external driver ICs. The 44-pin PLCC surface-mount package supports automated PCB assembly for high-volume scale production, and the commercial 0 C to +70 C range covers indoor retail and laboratory scales.
Recommended
Process Monitor Readouts
Industrial process monitors (pressure, flow, level, temperature indicators) in factory floors benefit from the MAX131ACQH+'s built-in line-noise rejection, eliminating the need for digital filtering when measuring 4-20 mA or 0-10 V process signals. The on-chip LCD driver displays the process variable on a 3.5-digit readout directly, simplifying the panel-mount instrument design and reducing BOM cost. Designers condition the input with an external op-amp to scale 4-20 mA or thermocouple/RTD signals into the 0.2 V to 2.0 V ADC input range, then read the integrated 3.5-digit LCD output without an external microcontroller.
Recommended
Battery-Powered LCD Instrumentation
Battery-powered LCD instrumentation such as portable pH meters, conductivity meters, and gas detectors benefit from the MAX131ACQH+'s single 5 V supply operation and integrated LCD driver, which minimizes quiescent current and eliminates separate display-driver power. The integrating architecture consumes less average current than successive-approximation ADCs during conversion, extending battery life in handheld instruments. With the on-chip bandgap reference and on-chip oscillator, the designer needs only the external integrator and auto-zero capacitors plus the input signal conditioning to complete a full handheld meter, drastically reducing PCB size and BOM cost.
Recommended
Educational and Hobbyist Electronics Projects
Hobbyist multimeter projects, educational lab DPMs, and DIY panel-meter builds benefit from the MAX131ACQH+ because it is a single-chip solution integrating ADC, reference, clock, and LCD driver. The datasheet's typical application circuit shows a complete 3.5-digit voltmeter requiring only the MAX131ACQH+, an input attenuator, an integrator capacitor, an auto-zero capacitor, and a 3.5-digit LCD - making it ideal for teaching ADC principles. The PLCC-44 (QCCJ) surface-mount package requires careful PCB layout but is supported by breakout boards and SOIC-style adapter PCBs available from hobbyist suppliers.
Recommended
Recommended Products Summary
Engineering reference data for MAX131ACQH+ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX131ACQH+TD | MAX131AEQH+ | MAX131C/D |
|---|---|---|---|---|
| Brand | Maxim Integrated | Maxim Integrated - same | Maxim Integrated - same | Maxim Integrated - same |
| Package | PLCC-44 (QCCJ) | PLCC-44 (QCCJ) - same | PLCC-44 (QCCJ) - same | DIP-40 - different |
| Architecture | Dual-Slope Integrating | Dual-Slope Integrating - same | Dual-Slope Integrating - same | Dual-Slope Integrating - same |
| Resolution | 3.5 digits (2000 counts) | 3.5 digits | 3.5 digits | 3.5 digits |
| Input Voltage Range | 0.2 V to 2.0 V differential | 0.2 V to 2.0 V | 0.2 V to 2.0 V | 0.2 V to 2.0 V |
| Operating Temperature | 0 C to +70 C (Commercial) | 0 C to +70 C (Industrial screening) | -40 C to +85 C (Extended Industrial) | 0 C to +70 C (Commercial, ceramic) |
| Reference Type | Internal bandgap | Internal bandgap - same | Internal bandgap - same | Internal bandgap - same |
| Display Output | On-chip LCD driver (multiplexed) | On-chip LCD driver - same | On-chip LCD driver - same | On-chip LCD driver - same |
| Lead Free / RoHS | Yes (Pb-free, RoHS) | Yes (Pb-free, RoHS) | Yes (Pb-free, RoHS) | Yes (Pb-free, RoHS) |
Key Differentiators
- Integrated ADC + bandgap reference + LCD driver in one IC (vs MAX131AEQH+)
- Dual-slope integrating architecture with inherent 50/60 Hz rejection (vs MAX131C/D)
- Single +5 V supply operation with on-chip bandgap reference (vs MAX131ACQH+TD)
Design Notes
The MAX131ACQH+ operates from a single +5 V supply and draws approximately 1 mA typical quiescent current. Decouple the V+ pin to GND with a 0.1 uF ceramic capacitor placed as close as possible to the IC pins. For battery-powered applications, the integrating architecture inherently consumes less average current than successive-approximation ADCs during conversion because the integrator ramps linearly rather than switching at full current. Reference pin decoupling is also recommended per the datasheet typical application circuit.
External integrator (CINT) and auto-zero (CAZ) capacitor selection directly affects conversion accuracy, noise rejection, and conversion speed. Use polypropylene or polycarbonate capacitors for lowest dielectric absorption; standard ceramic or electrolytic capacitors will introduce non-linearity errors. Typical values are 0.047 uF to 0.47 uF; the datasheet's typical application circuit specifies exact values based on desired conversion speed. Do not substitute CAZ with a polarized capacitor in reverse polarity or with a high-leakage ceramic - it will cause zero-drift errors.
PCB layout for the MAX131ACQH+ must keep the analog input traces (IN+, IN-) short and away from the LCD segment driver traces, because the high-voltage LCD backplane switching can couple into the analog front-end and degrade conversion accuracy. Place the integrator and auto-zero capacitors close to the CINT and CAZ pins respectively. Route the digital supply (if any) separately from the analog supply, and place a ground pour under the analog section to provide shielding. The PLCC-44 package's center pad may be tied to GND for additional thermal dissipation.
Compliance Information
The '+' suffix denotes Pb-free (lead-free) construction; RoHS and REACH compliant per Maxim Integrated product page. Not AEC-Q100 qualified - not intended for automotive applications. Halogen-free status not explicitly stated in the verified data. Conflict-minerals compliance declared per Maxim/Analog Devices standard practice.
