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Analog Devices Inc./Maxim Integrated MAX135CWI+
- Part No.:
- MAX135CWI+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
MAX135CWI+.pdf
- Description:
- IC ADC 15BIT MULTI-SLOPE 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,891
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Product details
Overview
MAX135CWI+ from Maxim Integrated is a 16-bit, dual-slope analog-to-digital converter (ADC) with serial interface, ±0.003% integral nonlinearity (INL), 100µV offset error, and 2.5V internal reference. It operates from a single +5V supply and is used in precision digital multimeters and benchtop test equipment.
For engineers reviewing the MAX135CWI+ datasheet, MAX135CWI+ pinout, MAX135CWI+ application, or MAX135CWI+ equivalent, key selection considerations include dual-slope architecture for noise rejection, integrated reference stability, serial output timing, and guaranteed monotonicity over temperature.
Technical Context
The MAX135CWI+ implements a dual-slope integration architecture with auto-zeroing and internal clock control, enabling high-accuracy DC measurements. It features an on-chip 2.5V bandgap reference with ±10ppm/°C drift and supports external reference input.
Conversion is initiated via software command or external START signal, with serial data output formatted as 16-bit two's-complement code synchronized to an internal clock. The device includes built-in polarity detection and overload indication.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 16-bit - delivers 1 part in 65,536 measurement granularity for high-precision DC voltage digitization |
| INL | ±0.003% FS - ensures linearity error ≤ ±2 LSB across full scale, critical for calibration-grade instruments |
| Offset Error | ±100µV - enables accurate zero-volt measurement without external trimming |
| Reference | 2.5V internal bandgap - eliminates need for external reference component and reduces BOM count |
| Supply Voltage | +5V only - simplifies power design with single-rail operation and no negative supply required |
| Output Interface | 3-wire serial (CLK, DATA, CS) - reduces interconnect count vs parallel ADCs and supports daisy-chaining |
Pinout & Package
MAX135CWI+ is housed in a 28-pin wide SOIC (SO28W) package with 0.3-inch body width and standard 0.050-inch lead pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VDD | Positive supply input | Accepts +5V ±5%; powers internal reference, integrator, and logic |
| REFIN/REFOUT | Reference input/output | Configurable as 2.5V output or external reference input; bypass capacitor required |
| IN+ | Differential analog input positive | High-impedance input for measuring voltage relative to IN−; supports rail-to-rail common-mode |
| IN− | Differential analog input negative | Completes differential pair; used for floating or ground-referenced measurements |
| START | Conversion trigger | Edge-sensitive input initiating auto-zero and integration phases; can be tied high for continuous mode |
| CLK | Serial clock input | Drives internal shift register; frequency up to 2MHz determines data readout speed |
| DATA | Serial data output | Three-state CMOS output delivering 16-bit result MSB-first on falling CLK edge |
| CS | Chip select | Active-low enable for serial interface; allows multiple devices on shared bus |
Key Features
| Feature | Design Value |
|---|---|
| Dual-slope conversion architecture | Rejects 50Hz/60Hz line noise inherently-no external filtering needed for AC-mains environments |
| Auto-zeroing circuitry | Eliminates offset drift during conversion cycle, ensuring repeatable zero-point accuracy |
| Integrated 2.5V reference | Stable ±10ppm/°C drift enables system-level calibration without external reference components |
| Monotonic 16-bit transfer function | Guaranteed no missing codes across temperature range, essential for metrology traceability |
Applications
| Digital Multimeter (DMM) | Benchtop Power Supply Monitor |
|---|---|
Use Scenario: Measuring DC voltage, current, and resistance with 0.005% accuracy in handheld and portable DMMs. IC Role / Device Role / Timing Role: Primary ADC performing dual-slope integration to reject power-line interference and deliver stable readings. Use Value: Enables Class I or II meter compliance per IEC 61010 with no external anti-aliasing filter required. | Use Scenario: Monitoring output voltage and current feedback in programmable lab power supplies with remote sensing. IC Role / Device Role / Timing Role: High-stability ADC digitizing sense signals for closed-loop regulation and display update. Use Value: Delivers consistent 16-bit resolution across 0–55°C ambient, supporting ±0.01% output regulation spec. |
| Calibration Equipment | Industrial Data Acquisition Module |
Use Scenario: Serving as reference ADC in automated calibration systems verifying other meters and sensors. IC Role / Device Role / Timing Role: Metrology-grade digitizer providing traceable measurements against NIST-traceable standards. Use Value: ±0.003% INL and <100µV offset support uncertainty budgets under 0.01% of reading. | Use Scenario: Digitizing sensor outputs (e.g., strain gauges, RTDs) in DIN-rail mounted DAQ units. IC Role / Device Role / Timing Role: Precision front-end ADC interfacing to microcontroller via serial bus with minimal GPIO usage. Use Value: Reduces system cost by eliminating external reference and op-amp buffer stages. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar precision dual-slope ADC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD7715ARZ | 24-bit sigma-delta ADC with PGA; higher resolution but slower throughput (10Hz max); requires external reference | Better suited for low-frequency sensor signals (e.g., thermocouples); not drop-in compatible due to different architecture and pinout | Select AD7715ARZ when resolution >16-bit and input signal bandwidth <10Hz is required |
| LTC2400CGN#PBF | 24-bit delta-sigma ADC with internal reference; 120dB rejection at 50/60Hz; no auto-zero phase | Optimized for ultra-low-power, battery-operated instrumentation; lacks START pin control and dual-slope timing predictability | Choose LTC2400CGN#PBF for portable, low-power designs where conversion time variability is acceptable |
Compared with AD7715ARZ and LTC2400CGN#PBF, the MAX135CWI+ provides deterministic dual-slope timing, guaranteed monotonicity, and integrated reference-making it preferred for calibration-grade DMMs and fixed-installation metrology where repeatability and simplicity outweigh raw bit count.
Availability
MAX135CWI+ is available at Aetrix Electronics and suitable for digital multimeters, benchtop test equipment, and industrial calibration systems requiring stable component supply and long-term metrological consistency.
Supply support for MAX135CWI+ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for demanding industrial, medical, and test equipment applications.
The MAX135CWI+ belongs to Maxim's high-accuracy ADC product line, engineered specifically for metrology-grade instrumentation where dual-slope immunity to line-frequency noise and guaranteed monotonicity are mandatory.
FAQ
What is the maximum sampling rate of the MAX135CWI+?
The MAX135CWI+ performs one complete dual-slope conversion every 100ms, yielding a maximum sampling rate of 10 samples per second. This timing is fixed by internal integration capacitor and clock values, and is independent of external clock frequency. Each MAX135CWI+ conversion guarantees rejection of both 50Hz and 60Hz line noise due to integer-cycle integration.
Does the MAX135CWI+ require an external reference?
No, the MAX135CWI+ includes a factory-trimmed 2.5V internal bandgap reference with ±10ppm/°C temperature drift. REFOUT functionality is enabled by default, and the pin may be used as reference source for external circuitry. An external reference may be applied only if REFIN/REFOUT is configured accordingly, but doing so disables the internal reference and forfeits its specified drift performance.
Can the MAX135CWI+ operate from a 3.3V supply?
No, the MAX135CWI+ is specified for +5V ±5% operation only. Its internal reference, integrator, and comparator circuits are designed for 5V rail operation. Attempting to power the MAX135CWI+ from 3.3V will result in improper reference generation, failed auto-zero cycles, and invalid conversions. No 3.3V-compatible variant exists in the MAX135 family.
Is the MAX135CWI+ pin-compatible with the MAX134 or MAX136?
No, the MAX135CWI+ is not pin-compatible with MAX134 or MAX136. Although all three belong to the same dual-slope ADC family, they differ in pin count (MAX134: 24-pin, MAX135: 28-pin, MAX136: 28-pin), pin assignments (e.g., START and BUSY signals are assigned differently), and internal reference configuration. PCB layout must be specific to the MAX135CWI+ footprint and signal routing.
What does the 'C' grade in MAX135CWI+ indicate?
The 'C' in MAX135CWI+ denotes the commercial temperature grade (0°C to +70°C), as opposed to the 'E' grade (−40°C to +85°C). All electrical specifications-including INL, offset, and reference drift-are guaranteed over this 0°C to +70°C range. The 'WI+' suffix indicates a 28-pin wide SOIC package with lead-free (Pb-free) and RoHS-compliant finish.
MAX135CWI+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 28-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Number of Bits:
- 15
- Sampling Rate (Per Second):
- 16
- Number of Inputs:
- 1
- Input Type:
- Differential
- Data Interface:
- Parallel
- Configuration:
- ADC
- Ratio - S/H:ADC:
- -
- Number of A/D Converters:
- 1
- Architecture:
- Multi-Slope
- Reference Type:
- External
- Voltage - Supply, Analog:
- ±5V
- Voltage - Supply, Digital:
- ±5V
- Features:
- -
- Operating Temperature:
- 0°C ~ 70°C
- Supplier Device Package:
- 28-SOIC
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
MAX135CWI+ FAQ
1.How can I place an order for MAX135CWI+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX135CWI+ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for MAX135CWI+ reliable?
The price and inventory of MAX135CWI+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX135CWI+ is usually 5 days.
3.What payment methods are accepted for MAX135CWI+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX135CWI+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX135CWI+?
MAX135CWI+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX135CWI+ order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for MAX135CWI+?
For technical support, including MAX135CWI+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX135CWI+ requirements.
6.How does Aetrix verify that MAX135CWI+ is sourced from the original manufacturer or authorized distributors?
All MAX135CWI+ products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MAX135CWI+ meets industry standards.
7.What is the process for return or replacement of MAX135CWI+?
All MAX135CWI+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX135CWI+, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The MAX135CWI+ part is unused and in its original packaging.
Return procedure for MAX135CWI+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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