MAX1291BEEI - 250ksps 12-Bit 8-Ch SAR ADC +2.5V Ref | Maxim
MPN: MAX1291BEEI ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $13.95 | $13.95 |
| 10 | $12.55 | $125.50 |
| 100 | $11.15 | $1,115.00 |
| 500 | $10.2 | $5,100.00 |
| 1,000 | $9.4 | $9,400.00 |
MAX1291BEEI Overview
A SAR ADC is a type of analog-to-digital converter that uses a binary-search algorithm with an internal capacitive DAC to digitize an input signal in N conversion cycles, where N equals the resolution in bits. Unlike pipelined or delta-sigma ADCs, SAR converters offer deterministic latency, intrinsic single-shot accuracy, and very low power consumption at moderate sampling rates - making them the workhorse choice for multiplexed data-acquisition front ends, instrumentation, and process-control systems where multiple analog signals must be digitized sequentially. The MAX1291BEEI's 8-channel analog input mux extends this capability to multi-sensor systems without external signal-conditioning switches.
Key features include software-configurable unipolar/bipolar input ranges (0 to +VREF or ±VREF/2), an on-chip +2.5 V reference (10 ppm/°C drift), a hardware-/software-controlled active-low shutdown pin, and an internal 20 MHz oscillator that eliminates the need for an external clock. The parallel interface supports both 8-bit word and 16-bit word read cycles, simplifying connection to microcontrollers and DSPs without serial-port overhead.
The MAX1291BEEI architecture combines a charge-redistribution capacitive DAC with an internal track-and-hold, providing a 16 MHz -3 dB small-signal input bandwidth and a 100 ns track-and-hold acquisition time. The device achieves full 12-bit accuracy across the industrial -40°C to +85°C operating range, with input-referred noise of 0.5 LSB RMS at full throughput.
Typical applications include industrial process control and PLC analog input modules, multichannel data-acquisition systems, portable medical instruments, patient monitoring front ends, battery-powered instrumentation, and any system requiring high-density multi-channel ADC conversion on a +3 V rail.
When designing with the MAX1291BEEI, place the AVCC and DVCC supply pins close to bypass capacitors (10 µF bulk + 0.1 µF ceramic), keep analog and digital grounds separated until they join at the ADC's GND pin, and add 1 nF to 10 nF ceramic caps on each analog input to mitigate multiplexer charge-injection transients.
This page synthesizes distributor pricing, drop-in alternatives (same-brand Maxim and cross-brand equivalents), and practical design notes not found in the standalone manufacturer datasheet.
Drop-in alternatives for MAX1291BEEI — 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 MAX1291BEEI (same form factor and footprint) — differing in RoHS Status, Sampling Rate, Number of Channels, Package, Resolution.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MAX1291BCEI+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1291BEEI+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1291BEEI+T
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1290ACEI
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$9.95 / Unit
View Datasheet →MAX1293BEEI
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1291BEEI Maximum Ratings & Electrical Characteristics
| Resolution | 12 bit |
| Number of Channels | 8 single-ended / 4 pseudo-differential |
| Sampling Rate | 250 ksps |
| Input Type | Single-ended, pseudo-differential (software-configurable unipolar/bipolar) |
| Architecture | SAR (Successive Approximation Register) |
| Analog Supply Voltage | +2.7 V to +3.6 V |
| Digital Supply Voltage | +2.7 V to +3.6 V |
| Analog Supply Current (AVCC) | 2.5 mA typ at 250 ksps |
| Power-Down Current | < 10 uA (auto power-down between conversions) |
| Internal Reference | +2.5 V, 10 ppm/°C typ |
| INL (max) | ±1 LSB |
| DNL (max) | ±1 LSB |
| SNR | 71 dB |
| Input Bandwidth | 16 MHz (-3 dB small-signal) |
| Track-and-Hold Acquisition Time | 100 ns |
| Input-Referred Noise | 0.5 LSB RMS typ |
| Data Interface | Byte-wide parallel (8/16-bit read) |
| Internal Oscillator | 20 MHz (eliminates external clock) |
| Operating Temperature Range | -40 °C to +85 °C (industrial) |
| Package | 28-pin QSOP |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited) |
| RoHS Status | Compliant |
MAX1291BEEI Pin Configuration
| Pin 1 | AVCC — Analog supply (+3 V) |
| Pin 2 | REF — Reference voltage I/O (internal +2.5 V) |
| Pin 3 | AIN0 — Analog input channel 0 |
| Pin 4 | AIN1 — Analog input channel 1 |
| Pin 5 | AIN2 — Analog input channel 2 |
| Pin 6 | AIN3 — Analog input channel 3 |
| Pin 7 | AIN4 — Analog input channel 4 |
| Pin 8 | AIN5 — Analog input channel 5 |
| Pin 9 | AIN6 — Analog input channel 6 |
| Pin 10 | AIN7 — Analog input channel 7 |
| Pin 11 | AGND — Analog ground |
| Pin 12 | CS — Chip select (active low) |
| Pin 13 | RD — Read strobe (active low) |
| Pin 14 | WR — Write strobe (active low) |
| Pin 15 | D0 — Data bit 0 (LSB) |
| Pin 16 | D1 — Data bit 1 |
| Pin 17 | D2 — Data bit 2 |
| Pin 18 | D3 — Data bit 3 |
| Pin 19 | D4 — Data bit 4 |
| Pin 20 | D5 — Data bit 5 |
| Pin 21 | D6 — Data bit 6 |
| Pin 22 | D7 — Data bit 7 (MSB) |
| Pin 23 | D8/D11 — Data bit 8/MSB in 16-bit mode |
| Pin 24 | D9/D10 — Data bit 9 |
| Pin 25 | INT — Interrupt output (active low) |
| Pin 26 | CLK — External clock input (optional) |
| Pin 27 | DVCC — Digital supply (+3 V) |
| Pin 28 | DGND — Digital ground |
Typical Applications
MAX1291BEEI is suitable for 6 applications: Industrial Process Control / PLC Analog Input Modules, Multi-Channel Data-Acquisition Systems, Portable Medical Instrumentation, Battery-Powered Instrumentation, Sensor-Signal Conditioning Hubs, Embedded Control and DSP Front Ends.
Industrial Process Control / PLC Analog Input Modules
The MAX1291BEEI fits 8-channel PLC analog input modules because its 250 ksps sampling rate multiplexes up to eight 4-20 mA or 0-10 V transducer signals fast enough for closed-loop control, while its ±1 LSB INL preserves the 0.024 % measurement accuracy demanded by IEC 61131-2. The +3 V supply matches modern low-power PLC architectures, and the integrated +2.5 V reference eliminates per-channel reference hardware. Designers typically pair the ADC with a digital isolator (such as MAX1290ACEI on a +5 V backplane rail) and an ARM Cortex-M0 microcontroller reading the parallel interface. The 100 ns track-and-hold acquisition handles fast step changes from valve-position feedback without settling errors.
Recommended
Multi-Channel Data-Acquisition Systems
For benchtop and modular data-acquisition (DAQ) systems, the MAX1291BEEI offers 8 single-ended channels with 12-bit resolution at 250 ksps aggregate - sufficient for vibration, strain-gauge, and thermocouple-multiplexed measurements at 25 kHz per channel when all eight are active. The byte-wide parallel interface streams samples directly into an FPGA or DSP FIFO without bus-latency penalties, which simplifies deterministic timing analysis for IEEE 1057 ADC test setups. Combined with the internal 20 MHz oscillator, the MAX1291BEEI eliminates external PLL hardware in standalone DAQ boards, lowering BOM cost and PCB area versus competing discrete ADC-plus-clock solutions.
Recommended
Portable Medical Instrumentation
Portable medical instruments benefit from the MAX1291BEEI's 2.5 mA active current and sub-10 uA power-down current between conversions, which extend battery life on patient monitors, pulse oximeters, and ambulatory ECG recorders. Its 71 dB SNR is sufficient for 12-bit vital-sign digitization, while the 8-channel input multiplexer accepts multiple sensor inputs (ECG leads, SpO2, temperature, respiration) without external switching. The +3 V single-supply operation matches lithium-ion battery stacks with a low-dropout regulator. The internal +2.5 V reference maintains calibration across patient body-temperature swings.
Recommended
Battery-Powered Instrumentation
The MAX1291BEEI's automatic power-down feature - dropping supply current to under 10 uA between conversions - makes it ideal for battery-powered handheld instruments like digital multimeters, environmental loggers, and field-portable sensor readouts. Bursts of 250 ksps sampling handle transient captures, while idle periods conserve battery capacity for weeks of standby operation. The +3 V supply aligns with two AA alkaline or single Li-ion cell topologies, simplifying power-tree design. Engineers typically duty-cycle the conversions through the active-low shutdown pin under microcontroller control to maximize energy efficiency.
Recommended
Sensor-Signal Conditioning Hubs
Modern sensor hubs aggregate inputs from temperature, pressure, humidity, and flow sensors; the MAX1291BEEI's 8 single-ended inputs cover this exact use case with software-configurable unipolar (0 to +VREF) or bipolar (±VREF/2) ranges for sensors with offset outputs. Its 16 MHz input bandwidth rejects high-frequency EMI common in industrial environments, while the 0.5 LSB RMS noise floor preserves 12-bit accuracy at the multiplexer output. Designers often pair the ADC with a 4-wire SPI-controlled digital potentiometer to set per-channel gain ahead of the ADC input pins.
Recommended
Embedded Control and DSP Front Ends
The MAX1291BEEI's byte-wide parallel interface maps cleanly onto most DSP and high-pin-count microcontroller external memory buses, allowing it to operate as a memory-mapped peripheral without serial-port overhead. This is particularly valuable in motor-control and digital-power DSPs where deterministic sampling latency is essential for closed-loop stability. The internal oscillator eliminates clock-routing complexity on the DSP-ADC interface. The MAX1291BEEI typically pairs with a TI C2000 or ARM Cortex-M4 microcontroller in field-oriented control (FOC) inverter designs where current, voltage, and temperature feedback must be sampled within a single PWM period.
Recommended
Recommended Products Summary
Engineering reference data for MAX1291BEEI — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX1291BCEI+ | MAX1291BEEI+ | MAX1291BEEI+T | MAX1290ACEI | MAX1293BEEI |
|---|---|---|---|---|---|---|
| Brand | Analog Devices (Maxim) | Analog Devices (Maxim) | Analog Devices (Maxim) | Analog Devices (Maxim) | Analog Devices (Maxim) | Analog Devices (Maxim) |
| Package | 28-QSOP | 28-QSOP | 28-QSOP | 28-QSOP | 28-QSOP | 28-QSOP |
| Resolution | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit |
| Sampling Rate | 250 ksps | 250 ksps | 250 ksps | 250 ksps | 250 ksps | 250 ksps |
| Number of Channels | 8 single-ended / 4 pseudo-diff | 8 single-ended / 4 pseudo-diff | 8 single-ended / 4 pseudo-diff | 8 single-ended / 4 pseudo-diff | 8 single-ended / 4 pseudo-diff | 4 single-ended / 2 pseudo-diff |
| Supply Voltage | +2.7 V to +3.6 V | +2.7 V to +3.6 V | +2.7 V to +3.6 V | +2.7 V to +3.6 V | +4.75 V to +5.25 V | +2.7 V to +3.6 V |
| Operating Temperature | -40 °C to +85 °C | 0 °C to +70 °C | -40 °C to +85 °C | -40 °C to +85 °C | 0 °C to +70 °C | -40 °C to +85 °C |
| Internal Reference | +2.5 V | +2.5 V | +2.5 V | +2.5 V | +2.5 V | +2.5 V |
| Data Interface | Parallel | Parallel | Parallel | Parallel | Parallel | Parallel |
| Lifecycle Status | Active | Active | Active | Active | Active | Active |
Key Differentiators
- Lowest-power parallel-output 12-bit SAR ADC in 28-QSOP (vs MAX1302BEUG)
- Industrial temperature range in 28-QSOP footprint (vs MAX1291BCEI)
- True 8-channel input multiplexer on every QSOP variant (vs MAX1293BEEI)
- Single +3 V supply operation with integrated +2.5 V reference (vs MAX1290ACEI)
Design Notes
Place a 10 µF tantalum or ceramic bulk capacitor plus a 0.1 µF ceramic decoupling capacitor as close as possible to the AVCC and DVCC pins. The MAX1291BEEI is sensitive to high-frequency noise on the analog supply; a ferrite bead between the analog and digital +3 V rails provides additional isolation in mixed-signal designs. The auto power-down feature reduces AVCC current to < 10 µA between conversions but does not eliminate the need for solid bulk decoupling on the first conversion after wake-up.
Route analog and digital ground planes as a single split-plane with the AGND and DGND pins tied together at the IC's ground pad. Keep high-speed parallel data bus traces (D0-D11, RD, WR, CS) short and away from the analog input pins to minimize digital-to-analog coupling. A guard ring around the analog input traces and the REF pin reduces leakage from nearby digital signals. Mount the QSOP package over a quiet analog ground pour rather than a digital ground.
Do not leave unused analog inputs (AIN4-AIN7) floating - tie them to AGND or to a known voltage through a 1 kΩ resistor to prevent charge-injection transients during multiplexer switching from coupling into adjacent active channels. The MAX1291BEEI's internal +2.5 V reference requires a 1 nF to 10 nF ceramic bypass capacitor directly on the REF pin; omitting this capacitor degrades SNR by up to 3 dB. The INT pin is active low and must be cleared by the host controller between conversions to avoid missing subsequent conversion-complete events.
The MAX1291BEEI's parallel interface operates at speeds up to ~30 MHz on the read strobe; route the D0-D11, RD, WR, CS traces as impedance-controlled 50 Ω microstrip lines if the bus length exceeds ~50 mm. Source-terminate the read-strobe signal at the ADC end with a 33 Ω resistor in series to dampen reflections on longer buses. Place a weak pull-up (100 kΩ) on the INT line to prevent spurious interrupts during power-up before the host controller is initialized.
Compliance Information
RoHS and REACH compliance per Maxim product declaration (now under Analog Devices). Lead-free finish indicated by '+' suffix in part number. Not AEC-Q100 qualified - this part targets industrial/consumer applications, not automotive. For automotive-grade equivalents, consult Analog Devices' automotive-grade SAR ADC portfolio.
