MAX1138KEEE+ - 12-Channel 10-Bit SAR ADC, I2C, QSOP-16
MPN: MAX1138KEEE+ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $7.45 | $7.45 |
| 10 | $6.85 | $68.50 |
| 100 | $5.95 | $595.00 |
| 500 | $5.2 | $2,600.00 |
| 1,000 | $4.55 | $4,550.00 |
MAX1138KEEE+ Overview
A SAR ADC is a successive-approximation-register analog-to-digital converter that uses a binary search algorithm with an internal DAC and comparator to convert analog input voltages into digital codes within a single conversion cycle per bit. Within the broader hierarchy, the MAX1138KEEE+ is a multi-channel data converter -> ADC analog-to-digital converter -> data-acquisition IC -> mixed-signal semiconductor.
Key differentiating features include 12 single-ended analog input channels (vs. 4 channels on the MAX1136), an internal 2.5V reference, software-configurable unipolar/bipolar inputs, and an automatic channel-scanning state machine that cycles through selected channels sequentially. The part also integrates an internal oscillator and programmable acquisition time, eliminating the need for an external clock source.
Typical applications include portable data logging, patient monitoring, system supervision in embedded control, thermocouple/thermistor front-end digitisation, and battery-powered instrumentation where the small QSOP-16 footprint and low supply current (typically 200 µA at the lowest throughput) are decisive. The internal reference and track/hold simplify BOM cost and layout complexity.
When designing with this device, ensure the SCL/SDA pull-ups follow I2C bus specifications (typically 4.7 kΩ at 3.3V for Fast Mode) and that the AIN inputs respect the absolute-maximum input range to avoid latch-up. For best noise performance, place 0.1 µF bypass capacitors directly at VDD and use the internal reference rather than an external source.
This page synthesises distributor pricing, drop-in alternatives (including same-family Maxim parts and cross-brand ADI replacements), and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for MAX1138KEEE+ — 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 MAX1138KEEE+ (same form factor and footprint) — differing in Input Type, Package, Resolution, Interface, Internal Reference Voltage.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MAX1138KEEE+T
✅ Drop-In✓ In Stock
$3.55 / Unit
View Datasheet →MAX1139EEE+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1238EEE+T
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1137KEEE+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1067BCEE
✅ Drop-In✓ In Stock
$9.4 / Unit
View Datasheet →MAX1138KEEE+ Maximum Ratings & Electrical Characteristics
| Resolution | 10 bit |
| Architecture | SAR (Successive Approximation) |
| Number of Input Channels | 6, 12 (single-ended, software-configurable) |
| Input Type | Single-Ended, Pseudo-Differential |
| Supply Voltage | 2.7 V to 3.6 V or 4.5 V to 5.5 V |
| Number of ADC Channels | 12 |
| Interface | I2C-compatible 2-wire serial (400 kHz Fast Mode, 1.7 MHz High-Speed Mode) |
| Internal Reference Voltage | 2.5 V |
| Reference Type | Internal (external optional) |
| Track/Hold | Internal |
| Package | 16-QSOP (QSOP-16, 0.154" / 3.90 mm width) |
| Operating Temperature Range | -40 °C to +85 °C (industrial) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
MAX1138KEEE+ Pin Configuration
| Pin 1 | AIN0 — Analog input channel 0 |
| Pin 2 | AIN1 — Analog input channel 1 |
| Pin 3 | AIN2 — Analog input channel 2 |
| Pin 4 | AIN3 — Analog input channel 3 |
| Pin 5 | AIN4 — Analog input channel 4 |
| Pin 6 | AIN5 — Analog input channel 5 |
| Pin 7 | AIN6 — Analog input channel 6 |
| Pin 8 | AIN7 — Analog input channel 7 |
| Pin 9 | AIN8 — Analog input channel 8 |
| Pin 10 | AIN9 — Analog input channel 9 |
| Pin 11 | AIN10 — Analog input channel 10 |
| Pin 12 | AIN11 — Analog input channel 11 |
| Pin 13 | GND — Ground |
| Pin 14 | VDD — Positive supply voltage |
| Pin 15 | SDA — I2C serial data |
| Pin 16 | SCL — I2C serial clock |
Typical Applications
MAX1138KEEE+ is suitable for 6 applications: Portable Data Logging, Patient Monitoring Systems, Industrial System Supervision, Battery-Powered Instrumentation, Embedded Control and PLCs, Thermocouple / Thermistor Front-End Digitisation.
Portable Data Logging
The MAX1138KEEE+ fits portable data-logging applications thanks to its 12 single-ended analog inputs, internal 2.5V reference, internal track/hold, and low 200 µA typical supply current in a compact QSOP-16 footprint. With up to 12 channels the part can digitise multiple thermocouples, RTDs, strain gauges, or 4-20 mA loop shunts through one IC, simplifying the BOM and shrinking PCB area for handheld instruments and field loggers.
Recommended
Patient Monitoring Systems
In patient monitoring front-ends the MAX1138KEEE+ provides 12 channels of 10-bit digitisation for ECG leads, SpO2 sensor outputs, temperature probes, and respiration signals. The integrated 2.5V reference and internal clock remove the need for external precision components, while the I2C-compatible 2-wire interface (Fast Mode 400 kHz / High-Speed Mode 1.7 MHz) reduces microcontroller I/O pin count, critical for compact wearable designs.
Recommended
Industrial System Supervision
The MAX1138KEEE+ is well-suited to industrial system supervision where multiple supply rails, temperature sensors, and current shunts must be monitored simultaneously. Its 12 single-ended input channels enable direct connection to voltage dividers and 4-20 mA loop receivers, while the internal reference ensures repeatable readings across the -40 °C to +85 °C industrial temperature range without external precision components.
Recommended
Battery-Powered Instrumentation
For battery-powered instrumentation, the MAX1138KEEE+ integrates track/hold, voltage reference, and clock in a single QSOP-16 package, drawing only ~200 µA in active conversion mode and entering automatic shutdown between conversions. This minimises quiescent drain while still offering 10-bit resolution for temperature, battery voltage, and load-current measurements in handheld meters, portable test gear, and remote sensor nodes.
Recommended
Embedded Control and PLCs
Embedded controllers and small PLCs benefit from the MAX1138KEEE+'s 12 single-ended input channels, which allow direct connection to potentiometers, thermistors, photo-diodes, and analogue output transducers without external muxing. The I2C-compatible 2-wire interface supports up to 1.7 MHz High-Speed Mode, ensuring fast updates of process-control loops, while the QSOP-16 footprint suits compact control boards where board area is constrained.
Recommended
Thermocouple / Thermistor Front-End Digitisation
The MAX1138KEEE+ digitises thermocouple and thermistor bridge outputs directly with its 12 single-ended channels, internal 2.5V reference, and integrated track/hold. Software-configurable unipolar/bipolar input modes allow direct digitisation of thermocouple millivolt signals, and the small QSOP-16 footprint keeps the analogue front-end compact alongside the MCU in temperature-acquisition modules.
Recommended
Recommended Products Summary
Engineering reference data for MAX1138KEEE+ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX1138KEEE+T | MAX1139EEE+ | MAX1238EEE+T | MAX1137KEEE+ | MAX1067BCEE |
|---|---|---|---|---|---|---|
| Brand | Analog Devices (Maxim Integrated) | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | QSOP-16 | QSOP-16 - same | QSOP-16 - same | QSOP-16 - same | QSOP-16 - same | QSOP-16 - same |
| Resolution | 10 bit | 10 bit | 10 bit | 12 bit | 10 bit | 12 bit |
| Number of Input Channels | 6, 12 (single-ended) | 6, 12 | 12 SE / 6 pseudo-diff | 12 | 8 | 8 |
| Interface | I2C (400 kHz / 1.7 MHz) | I2C | I2C | I2C | I2C | I2C |
| Supply Voltage | 2.7-3.6 V / 4.5-5.5 V | 2.7-3.6 V / 4.5-5.5 V | 2.7-3.6 V / 4.5-5.5 V | 2.7-3.6 V / 4.5-5.5 V | 2.7-3.6 V / 4.5-5.5 V | 2.7-3.6 V / 4.5-5.5 V |
| Internal Reference | 2.5 V | 2.5 V | 2.5 V | 2.5 V | 2.5 V | 2.5 V |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C |
Key Differentiators
- Highest channel count in MAX1136-MAX1139 family with 12 channels (vs MAX1137KEEE+ (8 channels))
- Pin-compatible 12-bit upgrade path exists without PCB changes (vs MAX1136 (4 channels))
- Integrated reference, track/hold, and clock reduce BOM count (vs Discrete SAR ADC + external reference + external clock)
Design Notes
Place a 0.1 µF ceramic bypass capacitor as close as possible to the VDD pin and a 10 µF bulk capacitor at the supply rail. The MAX1138KEEE+ operates from 2.7V-3.6V or 4.5V-5.5V; do not operate at intermediate voltages (3.7V-4.4V) where the internal reference regulation is undefined.
The SDA and SCL pins are open-drain and must be pulled high with external pull-up resistors (typically 4.7 kΩ at 3.3V for Fast Mode 400 kHz, lower values such as 2.2 kΩ for High-Speed Mode 1.7 MHz). Without pull-ups the I2C bus will not function. Do not exceed the absolute maximum analog input voltage (VDD + 0.3 V) on any AIN pin to avoid latch-up.
Route analog input traces away from digital switching lines (SDA, SCL, MCU traces). Use a ground plane under the QSOP-16 footprint and place the device's GND pin directly to the analog ground plane. For best noise performance, use the internal 2.5 V reference with a 0.1 µF + 10 µF decoupling network on REF, instead of an external reference, unless absolute precision is required.
Compliance Information
RoHS compliant and lead-free per Maxim Integrated product page ('+' suffix denotes lead-free / RoHS-compliant packaging). REACH compliant per Maxim environmental documentation. Not AEC-Q100 qualified; for automotive-grade SAR ADCs consider MAX1138-MAX1139 automotive-grade variants if available.
