MAX155AEWI - 8-Ch 8-Bit ADC Simultaneous T/H +2.5V Ref
MPN: MAX155AEWI ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $21.5 | $21.50 |
| 10 | $19.85 | $198.50 |
| 100 | $17.4 | $1,740.00 |
| 500 | $15.95 | $7,975.00 |
| 1,000 | $14.4 | $14,400.00 |
MAX155AEWI Overview
An ADC (analog-to-digital converter) converts continuous analog signals into discrete digital codes, sitting between analog front-ends and digital processing blocks in any data-acquisition system. A successive-approximation register (SAR) ADC, the architecture used in the MAX155, performs bit-by-bit decisions against a reference in a single conversion clock cycle, trading high speed for moderate resolution. ADCs are a sub-category of data converters within the broader mixed-signal semiconductor family; the MAX155 adds simultaneous track-and-hold, an important innovation that lets up to 8 inputs be sampled within a few hundred nanoseconds of each other - critical for phase-coherent multichannel measurements where channel-to-channel skew would otherwise corrupt the result.
Key features include eight single-ended or four differential analog input channels, software-configurable unipolar/bipolar ranges, a +2.5 V internal bandgap reference (with optional external reference input), a throughput rate of 250 ksps with 6 microsecond conversion time, and power-down control that drops supply current to under 50 microamps for battery-sparing designs. The MAX155AEWI variant is specified for the -40 °C to +85 °C extended industrial temperature range and is offered in a wide-body 28-SOIC package for robust surface-mount assembly.
Inside the device, eight input track-and-hold blocks feed a single shared SAR core and DAC reference ladder; the +2.5 V reference is buffered and brought out to a pin for use by external sensor bridges or ratiometric networks, eliminating a separate reference IC. The parallel interface separates conversion control (WR) from data retrieval (RD), and the channel configuration RAM is addressable through a shared 8-bit bus - this dual mode was a common Maxim innovation in early 1990s data-acquisition parts and is still quoted in modern designs as a clean way to multiplex a single bus.
Typical applications include multi-channel data-acquisition front-ends in industrial process instrumentation, sensor array digitizers where simultaneous sampling is required (load-cell weigh scales, vibration monitoring, multi-phase power metering), portable instrumentation powered from +5 V rails, and embedded digital-control loops. The wide SOIC package, single-supply operation, and integrated reference make the part especially attractive for space-constrained designs that need many sampled channels.
When using the MAX155AEWI, ensure that the analog inputs remain within the common-mode range of the track-and-hold amplifiers (typically VDD - 1.5 V to GND) and that decoupling includes a 10 microfarad bulk capacitor plus a 0.1 microfarad ceramic close to each supply pin. Because the +2.5 V reference is brought out to a pin, it must be buffered with an op-amp if used to drive low-impedance loads.
This page consolidates distributor pricing, drop-in alternatives such as MAX155AEWI+, MAX155ACWI, MAX155BEWI and MAX155BCWI, plus practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for MAX155AEWI — 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 MAX155AEWI (same form factor and footprint) — differing in Package, Resolution, Input Type, RoHS Status, Data Interface.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MAX155AEWI+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX155ACWI
✅ Drop-In📋 Reference alternative (not in catalog)
MAX155BEWI
✅ Drop-In📋 Reference alternative (not in catalog)
MAX155BCWI
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1145BEAP+
✅ Drop-In✓ In Stock
$5.95 / Unit
View Datasheet →MAX1304ECM/V+
✅ Drop-In✓ In Stock
$12.5 / Unit
View Datasheet →MAX1309ECM/V+
✅ Drop-In✓ In Stock
$9.06 / Unit
View Datasheet →MAX155AEWI Maximum Ratings & Electrical Characteristics
| Resolution | 8 bit |
| Number of Channels | 8 single-ended / 4 differential |
| Sampling Rate | 250 ksps |
| Architecture | SAR with simultaneous track-and-hold |
| Input Type | Single-ended / differential, unipolar / bipolar |
| Reference | Internal +2.5 V (external override supported) |
| Supply Voltage | +5 V single supply |
| Data Interface | Parallel 8-bit with WR / RD control |
| Channel Configuration | Software-programmable via shared bus |
| Power-Down Mode | Yes, <50 microamp standby |
| Operating Temperature | -40 °C to +85 °C (extended industrial) |
| Package | 28-SOIC wide (0.295 in / 7.50 mm) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant (MAX155AEWI+); see compliance_info for legacy variant |
| Internal Track/Hold | 8 simultaneous T/H amplifiers, one per channel |
MAX155AEWI Pin Configuration
| Pin 1 | AIN1 — Analog input channel 1 |
| Pin 2 | AIN2 — Analog input channel 2 |
| Pin 3 | AIN3 — Analog input channel 3 |
| Pin 4 | AIN4 — Analog input channel 4 |
| Pin 5 | AIN5 — Analog input channel 5 |
| Pin 6 | AIN6 — Analog input channel 6 |
| Pin 7 | AIN7 — Analog input channel 7 |
| Pin 8 | AIN8 — Analog input channel 8 |
| Pin 9 | AGND — Analog ground return for inputs and reference |
| Pin 10 | VSS — Negative supply (typically ground) |
| Pin 11 | VDD — +5 V analog supply |
| Pin 12 | REF — +2.5 V internal reference output / external reference input |
| Pin 13 | D0 — Parallel data bit 0 (LSB) |
| Pin 14 | D1 — Parallel data bit 1 |
| Pin 15 | D2 — Parallel data bit 2 |
| Pin 16 | D3 — Parallel data bit 3 |
| Pin 17 | D4 — Parallel data bit 4 |
| Pin 18 | D5 — Parallel data bit 5 |
| Pin 19 | D6 — Parallel data bit 6 |
| Pin 20 | D7 — Parallel data bit 7 (MSB) |
| Pin 21 | WR — Write strobe for configuration / start of conversion |
| Pin 22 | RD — Read strobe for data retrieval |
| Pin 23 | CS — Chip-select input for bus arbitration |
| Pin 24 | INT — Interrupt / conversion-complete output |
| Pin 25 | PD/SHDN — Power-down / shutdown control input |
| Pin 26 | DGND — Digital ground return for bus logic |
| Pin 27 | NC — Not connected (per datasheet) |
| Pin 28 | NC — Not connected (per datasheet) |
Typical Applications
MAX155AEWI is suitable for 7 applications: Multi-Channel Industrial Data Acquisition, Vibration and Acoustic Monitoring, Three-Phase Power Metering, Portable and Battery-Powered Instrumentation, Embedded Control and Sensor Array Digitizers, Test and Measurement Front-End, Audio and Sonar Signal Capture.
Multi-Channel Industrial Data Acquisition
The MAX155AEWI's 8 single-ended (or 4 differential) input channels and integrated simultaneous track-and-hold amplifiers make it well suited to industrial data-acquisition front-ends where several sensors must be sampled within the same acquisition window. With 250 ksps throughput and 8-bit resolution, it provides enough bandwidth for vibration, temperature bridge and 4-20 mA-loop monitoring in a 28-SOIC wide footprint that mounts easily on a backplane PCB. The +2.5 V internal reference (also brought out to a pin for use by external sensor bridges) eliminates a separate reference IC, and power-down current under 50 microamps suits battery-backed remote telemetry units. Unlike external multiplexer-plus-ADC cascades, simultaneous T/H removes channel-to-channel skew so power-quality and phase-angle measurements stay accurate.
Recommended
Vibration and Acoustic Monitoring
For vibration monitoring of rotating machinery and acoustic beam-forming arrays, the phase relationship between multiple sensors is as important as the absolute amplitude. The MAX155AEWI's simultaneous track-and-hold on each of eight channels samples the entire transducer array within roughly 100 ns, preserving the inter-channel phase information that a sequential multiplexer would smear out. With 250 ksps aggregate throughput and an internal +2.5 V reference, eight accelerometer or microphone preamp outputs can be digitised directly into a host MCU, then FFT-processed for modal analysis or beam-steering. The wide 28-SOIC package makes hand-rework easy during prototype tuning of gain and offset per channel.
Recommended
Three-Phase Power Metering
Three-phase electricity meters require simultaneous sampling of the three phase voltages and three phase currents (and sometimes neutral) so that real, reactive and apparent power can be computed without phase error. The MAX155AEWI's 8 channels and simultaneous track-and-hold address this requirement directly, with 250 ksps aggregate sample rate supporting harmonics up to the 25th on a 50 Hz/60 Hz fundamental. The internal +2.5 V reference plus single +5 V supply simplifies the analog front end, while the wide 28-SOIC package fits comfortably on meter-form-factor boards. Compared with a multiplexer-and-ADC chain, simultaneous sampling eliminates the energy-metering error class that arises from channel skew during heavy non-linear loading.
Recommended
Portable and Battery-Powered Instrumentation
Field instruments such as handheld multimeter data-loggers, portable gas analysers and medical spot-check monitors often run from a single +5 V rail with strict power budgets. The MAX155AEWI's <50 microamp power-down current lets the device be duty-cycled between measurement bursts, while 250 ksps throughput ensures short acquisition windows for low-power duty ratio. The internal +2.5 V reference is brought out to a pin so it can drive external sensor bridges, eliminating the standby current of a separate reference IC. The 28-SOIC wide package is well supported by low-cost hand-rework tools used in instrument repair depots.
Recommended
Embedded Control and Sensor Array Digitizers
In PLC and embedded-control systems a single ADC often must read multiple analog inputs from sensors, potentiometers and supply monitors. The MAX155AEWI supports eight single-ended or four differential inputs, software-configurable through its shared parallel bus, allowing the host MCU to switch between operating modes without re-wiring. With 250 ksps throughput the loop-time remains well within a 1 kHz control update rate. The same +2.5 V reference also serves external ratiometric sensors such as strain-gauge bridges, removing the cost of a second reference in node-count-conscious designs.
Recommended
Test and Measurement Front-End
Bench instruments such as data loggers, multichannel oscilloscope front-ends and ATE stimulus/measurement boards benefit from the MAX155AEWI's simultaneous track-and-hold and +5 V single-supply operation. Up to 250 ksps aggregate sampling per channel enables capture of sub-millisecond transients when used with an external sample-and-hold, while the 8-channel count is enough for a four-wire-resistance plus four-thermocouple digitiser front-end. The internal +2.5 V reference offers low 50 ppm/°C typical drift, which is adequate for many bench applications without a separate precision reference.
Recommended
Audio and Sonar Signal Capture
Although 8-bit resolution limits the dynamic range, the MAX155AEWI's 250 ksps aggregate sample rate and 8 simultaneous channels are well suited to wide-bandwidth sonar and acoustic-array capture front-ends where phase coherence between channels is critical. Eight hydrophones or microphone pre-amp outputs can be sampled within nanoseconds of each other, preserving waveform phase for beam-forming or beam-steering algorithms downstream. The +5 V single-supply operation also makes the part attractive in underwater battery housings where power budget and PCB area are constrained.
Recommended
Recommended Products Summary
Engineering reference data for MAX155AEWI — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX155AEWI+ | MAX155ACWI | MAX155BEWI | MAX155BCWI |
|---|---|---|---|---|---|
| Brand | Analog Devices (Maxim Integrated) | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 28-SOIC wide (7.50 mm) | 28-SOIC wide (7.50 mm) | 28-SOIC wide (7.50 mm) | 28-SOIC wide (7.50 mm) | 28-SOIC wide (7.50 mm) |
| Resolution | 8 bit | 8 bit | 8 bit | 8 bit | 8 bit |
| Number of Channels | 8 single-ended / 4 differential | 8 / 4 | 8 / 4 | 8 / 4 | 8 / 4 |
| Sampling Rate | 250 ksps | 250 ksps | 250 ksps | 250 ksps | 250 ksps |
| Operating Temperature | -40 °C to +85 °C (extended industrial) | -40 °C to +85 °C | 0 °C to +70 °C (commercial) | -40 °C to +85 °C | 0 °C to +70 °C (commercial) |
| Input Range | Unipolar / bipolar, software-configurable | Unipolar / bipolar | Unipolar / bipolar | ±5 V bipolar | ±5 V bipolar |
| Internal Reference | +2.5 V yes, output to REF pin | +2.5 V yes | +2.5 V yes | +2.5 V yes | +2.5 V yes |
| Power-Down Current | <50 µA | <50 µA | <50 µA | <50 µA | <50 µA |
| RoHS Status | Check part marking (legacy MAX155AEWI non-RoHS) | RoHS compliant | Compliance check required | Compliance check required | Compliance check required |
Key Differentiators
- 8-channel simultaneous track-and-hold in a single IC (vs Multiplexer + single-channel ADC (e.g. cascaded MAX1154AEUE+T))
- Integrated +2.5 V bandgap reference with REF output (vs MAX1068AEEG+ (12-bit) used alone)
- Single +5 V supply with bipolar input ranges (vs MAX1304ECM/V+ (12-bit successor))
- <50 µA power-down current for duty-cycled designs (vs MAX1145BEAP+ (4-channel 12-bit))
Design Notes
Estimated: Decouple VDD with a 10 µF tantalum plus a 0.1 µF ceramic placed within 5 mm of the supply pin, returning to AGND. The MAX155AEWI's simultaneous track-and-hold is sensitive to supply ripple on VDD; a ferrite bead between the digital +5 V supply and the ADC's analog +5 V rail is recommended for noisy industrial buses. The PD/SHDN pin should be driven by a clean logic-level signal rather than a pulled-up GPIO to guarantee clean wake-up characteristics.
Separate analog (AGND) and digital (DGND) ground returns must be tied together only at one point under the REF decoupling capacitor. The 28-SOIC wide footprint allows the analog inputs AIN1-AIN8 to fan out symmetrically without crossing the digital bus (D0-D7 / WR / RD / CS / INT) - never route the digital bus under or next to the analog input traces, as capacitive coupling injects ADC-noise spikes directly into the T/H capacitors.
When using all eight single-ended inputs with a shared ground-referenced source, the input bandwidth of the internal T/H (typically several MHz) is sufficient but a 100 Ω series resistor plus 100 pF to AGND on each input pin creates a low-pass filter that limits RF pickup. For differential mode (4 channels) the two inputs of each pair must be DC- and AC-balanced through matched source impedances, otherwise the common-mode rejection is degraded and dynamic range suffers.
Do not load the REF pin with more than the datasheet-mandated external current, or the internal +2.5 V reference will drift and invalidate the ADC's full-scale calibration. If a buffer op-amp is needed for the REF pin, choose a low-bias CMOS-input part such as the MAX4165 family rather than a low-cost bipolar type that would inject bias current into the reference node. Also avoid operating the MAX155AEWI from a +5 V rail shared with switching regulators without LC filtering, as converter switching noise couples through VDD and appears at the converted data.
Compliance Information
The legacy MAX155AEWI (no '+') suffix predates the RoHS lead-free transition, so its RoHS status is uncertain and should be confirmed with the supplier lot by lot. The MAX155AEWI+ with '+' suffix is the modern RoHS-compliant / lead-free variant and is recommended for any new design. Automotive AEC-Q100 qualification is not applicable for this part; AEC-Q100 variants are not offered.
