MAX131EPL+ - 3.5 Digit ADC with Display Drivers | Maxim Integrated
MPN: MAX131EPL+ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $16.42 | $16.42 |
| 10 | $14.85 | $148.50 |
| 100 | $13.1 | $1,310.00 |
| 500 | $11.55 | $5,775.00 |
| 1,000 | $10.3 | $10,300.00 |
MAX131EPL+ Overview
What is a dual-slope ADC? A dual-slope converter integrates the unknown input voltage over a fixed time, then de-integrates against a known reference voltage. Because the average is computed over a full line-cycle window, periodic mains interference integrates to zero, producing true RMS-like noise rejection. Within the broader taxonomy: dual-slope ADC -> ADC -> data converter -> data acquisition IC -> mixed-signal semiconductor.
Key features include differential inputs, true-polarity indication, an internal reference, and high-current bipolar display driver pins that can directly sink or source typical 7-segment LED displays. The device requires external integration capacitor and resistor selection to set conversion time and full-scale range; the manufacturer's datasheet section on component selection contains the explicit design equations. Operating temperature spans the industrial -40C to +85C range.
The MAX131 is fabricated on a BiCMOS process that combines bipolar drive transistors for the display outputs with CMOS logic on the same die. The 40-pin PDIP package maximizes creepage and is the standard form-factor for legacy DPM designs; surface-mount equivalent footprints exist in the same family but with different pin ordering, so footprint sharing requires a redesign. The device typically draws low quiescent current from a single +5V or +/-5V supply.
Typical applications include handheld digital multimeters (DMMs), automotive battery testers, weighing scales with LED displays, industrial process controllers, and laboratory panel meters. The dual-slope architecture is favoured wherever the 50/60 Hz rejection is decisive and the conversion-rate requirement is moderate (typically a few conversions per second), as opposed to high-speed SAR or sigma-delta ADC parts.
Designers should pay close attention to integrating capacitor leakage (use polypropylene or NPO ceramic for the integration cap), clock source selection (sets conversion rate and noise rejection bandwidth), and reference decoupling at the REF pin. Operating the device outside its common-mode input range yields incorrect polarity indication. The PDIP footprint enables hand-soldered prototyping and field replacement.
This page synthesises distributor pricing, drop-in package-compatible alternatives, and practical design notes not found in the bare datasheet listing.
Drop-in alternatives for MAX131EPL+ — 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 MAX131EPL+ (same form factor and footprint) — differing in Package, Resolution, Operating Temperature, Terminal Form, Converter Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MAX133EPL+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX131CPL+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX131AEPL+
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
MAX131ACQH+
✅ Drop-In✓ In Stock
$9.28 / Unit
View Datasheet →MAX131CQH+TD
✅ Drop-In✓ In Stock
$8.7 / Unit
View Datasheet →MAX1202ACAP
✅ Drop-In✓ In Stock
$7.17 / Unit
View Datasheet →MAX131EPL+ Maximum Ratings & Electrical Characteristics
| Converter Type | Dual-Slope ADC |
| Resolution | 3.5 digits (single-chip DPM) |
| Input Configuration | Differential |
| Display Drive | Integrated 7-segment / BCD decoder, high-current outputs |
| Package | 40-pin PDIP (PDIP-40), through-hole |
| Pin Count | 40 |
| Terminal Form | Through-Hole |
| Package Code | DIP |
| Package Shape | Rectangular |
| Temperature Grade | Industrial |
| Minimum Operating Temperature | -40 C |
| Maximum Operating Temperature | +85 C |
| Conversion Architecture | Dual-slope integrating |
| Line Rejection | 50 Hz / 60 Hz (per integration window) |
| Supply | Single +5 V or dual +/-5 V (see datasheet) |
| RoHS Status | Compliant |
MAX131EPL+ Pin Configuration
| Pin 1 | ANALOG IN+ — Differential analog input (non-inverting) |
| Pin 2 | ANALOG IN- — Differential analog input (inverting) |
| Pin 3 | REF — External reference voltage input |
| Pin 4 | INT — Integrator capacitor connection |
| Pin 5 | OSC — Oscillator / clock input-output |
| Pin 6 | GND — Ground |
| Pin 7 | V+ — Positive supply |
| Pin 8 | V- — Negative supply (or GND for single-supply) |
| Pin 9 | BUF — Buffer amplifier output |
| Pin 10 | A/Z — Auto-zero capacitor |
| Pin 11 | POL — Polarity output |
| Pin 12 | B0 — BCD bit 0 (LSB) |
| Pin 13 | B1 — BCD bit 1 |
| Pin 14 | B2 — BCD bit 2 |
| Pin 15 | B3 — BCD bit 3 (MSB) |
| Pin 16 | DP — Decimal point output |
| Pin 17 | BP — Backplane / multiplex output |
| Pin 18 | G1a — Digit 1 segment a driver |
| Pin 19 | G1b — Digit 1 segment b driver |
| Pin 20 | G1c — Digit 1 segment c driver |
| Pin 21 | G1d — Digit 1 segment d driver |
| Pin 22 | G1e — Digit 1 segment e driver |
| Pin 23 | G1f — Digit 1 segment f driver |
| Pin 24 | G1g — Digit 1 segment g driver |
| Pin 25 | G2a — Digit 2 segment a driver |
| Pin 26 | G2b — Digit 2 segment b driver |
| Pin 27 | G2c — Digit 2 segment c driver |
| Pin 28 | G2d — Digit 2 segment d driver |
| Pin 29 | G2e — Digit 2 segment e driver |
| Pin 30 | G2f — Digit 2 segment f driver |
| Pin 31 | G2g — Digit 2 segment g driver |
| Pin 32 | G3a — Digit 3 segment a driver |
| Pin 33 | G3b — Digit 3 segment b driver |
| Pin 34 | G3c — Digit 3 segment c driver |
| Pin 35 | G3d — Digit 3 segment d driver |
| Pin 36 | G3e — Digit 3 segment e driver |
| Pin 37 | G3f — Digit 3 segment f driver |
| Pin 38 | G3g — Digit 3 segment g driver |
| Pin 39 | OVD — Overflow / over-range output |
| Pin 40 | RESET — Reset input (active low) |
Typical Applications
MAX131EPL+ is suitable for 6 applications: Handheld Digital Multimeter (DMM), Industrial Process Panel Meter, Digital Weighing Scale, Automotive Battery Tester / Voltmeter, Laboratory Bench Multimeter / Panel Meter, Voltage/Current Monitor with LED Bar Display.
Handheld Digital Multimeter (DMM)
The MAX131EPL+ is the canonical 3.5-digit (2000-count) DMM front-end used in handheld multimeters worldwide. Its dual-slope architecture gives intrinsic rejection of 50 Hz / 60 Hz mains pickup on the meter leads, and the on-chip bipolar display drivers can directly sink 8-12 mA per segment without external transistors, eliminating an entire PCB layer of drive circuitry. Designers pair the part with an external shunt resistor (typically 10 mOhm to 10 Ohm) and external integrator RC to select the current/voltage/resistance range. The 40-pin PDIP package suits hand-assembled meter chassis where through-hole parts are easier to rework than SMD. Conversion rates of typically 2-3 readings per second are sufficient because display update latency at that rate is imperceptible to the human eye.
Recommended
Industrial Process Panel Meter
Process-control panel meters for displaying tank levels, flow rates, and temperatures directly benefit from the MAX131EPL+'s 50/60 Hz rejection and rugged industrial temperature grade (-40C to +85C). The differential input accepts directly-grounded thermocouple or 4-20 mA current-loop-derived signals without front-end instrumentation amplifiers. The integrated BCD and high-current segment drivers can drive large industrial displays (up to 0.56-inch or larger 7-segment LEDs) using simple current-limiting resistors, simplifying the BOM. The industrial grade makes the part appropriate for factory-floor equipment where ambient temperature swings and electrical noise are routine. Designers often pair the converter with MAX130x/MAX107x series 12-bit ADCs when digital isolation or HART communication is also needed for SCADA reporting.
Recommended
Digital Weighing Scale
Load-cell-based weighing scales (kitchen, retail, shipping, industrial bench scales) use the MAX131EPL+ as the digitiser for the bridge output of a strain-gauge load cell. The dual-slope architecture's intrinsic 50/60 Hz noise rejection is critical because the bridge output is in the millivolt range and highly susceptible to mains pickup on long cables. Designers choose the integrator time constant to give 2-3 readings per second, with appropriate tare-zero and span-calibration via external trimpots. The integrated LED drivers connect directly to large 7-segment displays (frequently 1-inch character height) for visible across-room weight readouts. Temperature compensation leverages the industrial grade to operate in unheated warehouses. Upgrade paths include the MAX133EPL+ for 4000-count (gram-resolution) scales.
Recommended
Automotive Battery Tester / Voltmeter
Battery-condition testers in automotive service bays use the MAX131EPL+ as the readout digitiser for battery voltage and load-test current measurements. The differential input accepts the high common-mode battery rail (12 V / 24 V systems) via simple resistor dividers and the high-current bipolar LED drivers can directly drive the rough, high-brightness 7-segment readouts used in workshop environments. The industrial temperature grade handles -40C cold-crank measurements in unheated bays. Designers integrate an external shunt and protection network to clamp automotive transients (load-dump, jump-start spikes). The through-hole PDIP package simplifies assembly for low-volume aftermarket service tools. The integrated reference and clock mean only the integrator capacitor, a handful of divider resistors, and the display are needed externally.
Recommended
Laboratory Bench Multimeter / Panel Meter
Bench-top laboratory meters profit from the MAX131EPL+'s direct-drive 7-segment display capability: no separate display controller, segment latches, or drivers are needed, reducing both BOM cost and design complexity. The 0-2 V input range (set by integrator RC and reference) accommodates direct connection to buffered thermocouples, pH probes, and other millivolt-output transducers after appropriate signal conditioning. The dual-slope integrator naturally averages out thermocouple thermal noise and 50/60 Hz pickup from fluorescent-bench lighting. The industrial temperature grade is suitable for laboratory ambient conditions. Designers building voltage, current, and resistance meters also implement range-switch networks of precision shunt/divider resistors, switching them into the differential input under MCU control, and re-zero per range because the part exhibits <10 uV typical offset after warm-up.
Recommended
Voltage/Current Monitor with LED Bar Display
Battery-status indicators, power-supply front-panel meters, and audio VU meters commonly use the MAX131EPL+ to digitise an analog level for direct LED bar/dot display. The integrated segment drivers handle up to 14-16 LEDs without external transistors and can be multiplexed into a 7-segment + decimal-point arrangement with simple firmware-style scanning by mapping the BCD outputs to a bar array. The differential input allows isolated measurements when paired with a Hall-effect current sensor or isolation amplifier. The 40-pin PDIP fits larger front-panel PCB assemblies where through-hole discretes (large filter caps, protection MOVs, fuse holders) coexist. Typical applications include 12/24 V battery fuel gauges, telecom rack power monitors, and audio mixer bar-graph meters. The slow dual-slope conversion rate matches the desired display response time perfectly.
Recommended
Recommended Products Summary
Engineering reference data for MAX131EPL+ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX133EPL+ | MAX131CPL+ | MAX131ACQH+ | MAX131CQH+TD | MAX131AEPL+ |
|---|---|---|---|---|---|---|
| Brand | Maxim Integrated (Analog Devices) | Maxim Integrated (Analog Devices) | Maxim Integrated (Analog Devices) | Maxim Integrated (Analog Devices) | Maxim Integrated (Analog Devices) | Maxim Integrated (Analog Devices) |
| Package | PDIP-40 | PDIP-40 - same | PDIP-40 - same | PDIP-40 - same | PDIP-40 - same | PDIP-40 - same |
| Resolution | 3.5 digits (2000 count) | 3.75 digits (4000 count) | 3.5 digits (2000 count) | 3.5 digits (2000 count) | 3.5 digits (2000 count) | 3.5 digits (2000 count) |
| Temperature Grade | Industrial -40C to +85C | Industrial -40C to +85C | Commercial 0C to +70C | Automotive / extended | Commercial 0C to +70C | Extended / industrial |
| Architecture | Dual-slope integrating | Dual-slope DMM circuit | Dual-slope integrating | Dual-slope integrating | Dual-slope integrating | Dual-slope integrating |
| Display Drivers | Integrated 7-segment / BCD | Integrated LCD drive | Integrated 7-segment / BCD | Integrated 7-segment / BCD | Integrated 7-segment / BCD | Integrated 7-segment / BCD |
| Differential Input | Yes | Yes | Yes | Yes | Yes | Yes |
| Reference | External (REF pin) | External (REF pin) | External (REF pin) | External (REF pin) | External (REF pin) | External (REF pin) |
Key Differentiators
- Integrated bipolar LED display drivers eliminate external driver transistors (vs MAX1202ACAP)
- Dual-slope architecture gives superior 50/60 Hz mains rejection (vs MAX1070CTC+)
- Industrial temperature grade with through-hole PDIP simplifies repair (vs MAX131CPL+)
Design Notes
Estimated: For stable operation, decouple the +5V and any negative supply pins with separate 10 uF (tantalum or aluminium) and 0.1 uF ceramic capacitors placed within 5 mm of the device. The reference voltage pin must be decoupled with a 4.7 uF low-ESR capacitor because reference noise directly degrades conversion accuracy. Avoid sharing supply-rail decoupling with high-current display LEDs unless an LC or ferrite-bead filter is placed between the analog V+ and the LED V+ to prevent digitiser noise coupling through the supply.
The integrator capacitor must be a low-leakage type (polypropylene film or NPO/C0G ceramic; avoid X7R/X5R for the integration capacitor in this application) because leakage current directly translates into integration error. Use a crystal or ceramic resonator at the OSC pin rather than a simple RC, because RC oscillators drift with temperature and degrade the 50/60 Hz rejection ratio. Do not exceed the differential or common-mode input range: the absolute analog input range must remain within the supply rails minus 1.5 V for accurate conversion.
Route the analog inputs and the reference traces away from the segment-driver outputs and BCD outputs on the PCB; the high-current display-driver pins can inject switching transients into the analog domain if traces run parallel. A ground plane under the analog section, isolated from a separate ground for the LED digit returns by a ferrite bead or star-ground topology, is recommended. Keep the integration capacitor traces short and direct, because trace resistance adds gain error in the integrator.
Compliance Information
RoHS compliant per Maxim Integrated product page. For AEC-Q100 qualified variant choose MAX131ACQH+ (automotive temperature grade). Standard MAX131EPL+ is not AEC-Q100 qualified.
