MAX1285BCSA - 12-Bit 300ksps ADC, 3V, Serial | Maxim
MPN: MAX1285BCSA ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.5 | $8.50 |
| 10 | $7.78 | $77.80 |
| 100 | $6.95 | $695.00 |
| 500 | $6.18 | $3,090.00 |
| 1,000 | $5.4 | $5,400.00 |
MAX1285BCSA Overview
A SAR (Successive Approximation Register) ADC is a sampling converter that resolves an analog input in N cycles of its internal clock, one bit per cycle, using a switched-capacitor DAC and a comparator. SAR ADCs are preferred for multiplexed data-acquisition and instrumentation because they provide deterministic latency, no pipeline delay, excellent DC linearity, and inherently low power consumption that scales roughly with sample rate. In the converter hierarchy, the MAX1285 sits as a low-power serial 12-bit SAR ADC inside the broader precision-ADC category, ranking above 8/10-bit ADCs in resolution but below 14/16/18-bit SAR and delta-sigma ADCs in DC accuracy.
Key features include 300 ksps sampling rate (the MAX1284 sibling reaches 400 ksps at 5 V), 12-bit resolution with no missing codes, an internal +2.5 V reference (also externally overridable), a true-differential analog input stage, single +2.7 V to +3.6 V analog supply, and 2.5 mA typical operating supply current. The serial interface is SPI/QSPI/MICROWIRE-compatible, and the 8-pin SO footprint keeps the PCB area below 30 mm².
Typical applications include portable data-acquisition modules, remote battery-powered sensor read-out, process-control front ends, and pen-screen / touch-screen digitizers. The internal reference plus 3 V operation make it especially attractive for hand-held instrumentation.
When designing with this part, place the 0.1 µF supply bypass capacitor within 5 mm of the VDD pin and keep the REF decoupling (typically 4.7 µF) close to the REF pad. To minimize digital feedback into the analog path, route the DOUT and SCLK traces over a continuous ground plane and avoid running them parallel to the input trace.
This page synthesizes distributor pricing for the MAX1285BCSA / MAX1285BCSA+ variants, drop-in same-package alternatives, and practical PCB and reference design notes not found in the manufacturer datasheet.
Drop-in alternatives for MAX1285BCSA — 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 MAX1285BCSA (same form factor and footprint) — differing in Package, Resolution, RoHS Status, Sampling Rate, Architecture.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MAX1285BCSA+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1285BCSA+T
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1285BESA+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1285BESA+T
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1284BCSA
✅ Drop-In✓ In Stock
$9.95 / Unit
View Datasheet →MAX1285BCSA Maximum Ratings & Electrical Characteristics
| Part Number | MAX1285BCSA |
| Resolution | 12 bits |
| Number of Inputs | 1 single-ended (true-differential input stage) |
| Sampling Rate (max) | 300 ksps |
| Architecture | SAR (Successive Approximation) |
| Input Supply Voltage (Analog/Digital) | +2.7 V to +3.6 V (single supply) |
| Internal Reference Voltage | +2.5 V |
| Supply Current (operating) | 2.5 mA (typical) |
| Interface | Serial, SPI/QSPI/MICROWIRE-compatible |
| Track/Hold Bandwidth | Wide-bandwidth T/H (per datasheet) |
| Package | 8-pin SOIC (SO-8, narrow body) |
| Operating Temperature Range | 0 °C to +70 °C (commercial, "BCSA" suffix) |
| Pin Count | 8 |
| Mounting Type | Surface Mount |
| Lead-Free (MAX1285BCSA+ suffix) | Yes (Pb-free Sn/Ag/Cu lead finish; the "+" suffix denotes lead-free version) |
MAX1285BCSA Pin Configuration
| Pin 1 | AVDD — Analog supply (+2.7 V to +3.6 V); bypass with 0.1 µF + 10 µF to GND |
| Pin 2 | AIN — Analog input (true-differential) to T/H and SAR core |
| Pin 3 | GND — Analog/digital ground |
| Pin 4 | CS — Active-low chip-select for the serial interface |
| Pin 5 | DOUT — Serial data output (MSB first, SPI/QSPI/MICROWIRE) |
| Pin 6 | SCLK — Serial clock input (SPI/QSPI/MICROWIRE) |
| Pin 7 | DVDD — Digital supply (+2.7 V to +3.6 V); typically tied to AVDD |
| Pin 8 | REF — Internal +2.5 V reference; bypass with 4.7 µF; can be overdriven by external ref |
Typical Applications
MAX1285BCSA is suitable for 6 applications: Portable Data-Acquisition Modules, Remote Battery-Powered Sensor Read-Out, Process-Control Front End, Pen-Screen / Touch-Screen Digitizer, Hand-Held Test & Measurement Instrument, Medical Sensor Interface (Battery-Type Patient Monitor).
Portable Data-Acquisition Modules
The MAX1285BCSA's single +2.7 V to +3.6 V supply rail and 2.5 mA operating current let it run directly from a Li-ion or 3.3 V system rail, eliminating the boost converter that a 5 V ADC like the MAX1284 would require. Its 300 ksps throughput at 12 bits handles general-purpose sensor logging (thermistors, pressure transducers, strain gauges) at sub-mW power, with SPI serial output going straight to a low-power MCU such as the MSP430 or Cortex-M0+. Compared with higher-resolution sigma-delta ADCs, the SAR settling behaviour avoids pipeline delay so a burst of 300,000 samples/s is achievable from a moving sensor source.
Recommended
Remote Battery-Powered Sensor Read-Out
Stand-alone wireless sensor nodes (LoRa, BLE, Zigbee) need an ADC that pulls microamps to milliamps rather than tens of milliamps - exactly where the MAX1285BCSA's 2.5 mA operating current and power-down mode fit. The 3 V supply matches a primary Li-ion or 2xAA cell stack, the internal +2.5 V reference removes the need for an external reference IC, and the 8-pin SOIC keeps the PCB below 30 mm². For 1 kHz sampling duty cycles the part averages below 100 µA, well within a coin-cell energy budget.
Recommended
Process-Control Front End
Industrial 4-20 mA loop transmitters, PLC analog input cards, and HVAC controllers typically run on a 24 V backplane but need a 3.3 V local rail - the MAX1285BCSA's 3 V operation and true-differential input stage let it sit directly behind a resistive current-sense or 0-10 V divider. Its 300 ksps throughput captures fast step changes in process variables, and the SPI bus connects to a host MCU/CPLD over a few centimetres of FR4. The SAR architecture delivers deterministic latency so the controller can react in a fixed time after a sample request.
Recommended
Pen-Screen / Touch-Screen Digitizer
Resistive touch panels and pen-tablet digitizers generate rapidly-changing analog voltages that an MCU must sample at several hundred ksps to track pen motion smoothly. The MAX1285BCSA's 300 ksps throughput provides enough bandwidth for a 1024-level digitizer while its 12-bit resolution yields sub-pixel position resolution when paired with a 4-wire resistive panel. The serial interface requires only three MCU pins (CS, SCLK, DOUT), leaving more GPIO available for the LCD driver and buttons.
Recommended
Hand-Held Test & Measurement Instrument
A 3 V battery-powered multimeter or oscilloscope probe uses the MAX1285BCSA as the input digitizer for DC voltage and low-bandwidth measurement channels. Its 2.5 mA operation preserves battery life, the internal +2.5 V reference gives 0.1 %-class transfer accuracy when used at moderate temperatures, and the SOIC-8 footprint fits inside a pen-style probe housing. The SAR architecture's single-cycle latency means a 'single-shot' button press produces a deterministic reading within one conversion cycle.
Recommended
Medical Sensor Interface (Battery-Type Patient Monitor)
Battery-type patient monitors for pulse oximetry, ECG, or temperature need a low-noise, low-power 12-bit ADC that can digitize amplified sensor outputs without injecting ripple into the analog front end. The MAX1285BCSA's 2.5 mA operating current and internal +2.5 V reference keep the total front-end power budget low while its SAR settling preserves the kHz-bandwidth signals from a photodiode preamp. The SPI output isolates the noisy digital MCU from the analog chain, an important property when the MCU is also driving an LCD or wireless link.
Recommended
Recommended Products Summary
Engineering reference data for MAX1285BCSA — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX1285BCSA+ | MAX1285BESA+ | MAX1284BCSA |
|---|---|---|---|---|
| Brand | Analog Devices / Maxim Integrated | Analog Devices / Maxim Integrated - same | Analog Devices / Maxim Integrated - same | Analog Devices / Maxim Integrated - same |
| Package | SOIC-8 (SO-8, narrow body) | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same |
| Resolution | 12 bits | 12 bits | 12 bits | 12 bits |
| Maximum Sample Rate | 300 ksps | 300 ksps | 300 ksps | 400 ksps (+33%) |
| Supply Voltage Range | +2.7 V to +3.6 V | +2.7 V to +3.6 V | +2.7 V to +3.6 V | +4.5 V to +5.5 V (5 V rail) |
| Operating Temperature Range | 0 °C to +70 °C (Commercial) | 0 °C to +70 °C (Commercial) | -40 °C to +85 °C (Industrial) | 0 °C to +70 °C (Commercial) |
| Internal Reference Voltage | +2.5 V | +2.5 V | +2.5 V | +2.5 V |
| Serial Interface | SPI/QSPI/MICROWIRE compatible | SPI/QSPI/MICROWIRE | SPI/QSPI/MICROWIRE | SPI/QSPI/MICROWIRE |
Key Differentiators
- Pin-compatible drop-in upgrade path to higher sample rate (vs MAX1284BCSA)
- Industrial temperature grade version available in same package (vs MAX1285BESA+)
- Lead-free and RoHS-compliant modern ordering suffix (vs MAX1285BCSA (non-"+"))
Design Notes
Decouple AVDD and DVDD with a 0.1 µF X7R ceramic in parallel with a 10 µF tantalum/ceramic, placing both within 5 mm of the package pins; the datasheet specifies the supply-rejection performance with these capacitors in place. Tie AVDD and DVDD together at a single star-via if the rails are common; if you need separate rails (e.g. digital 3.3 V with a 3.0 V analog LDO) keep the delta below 50 mV and add a ferrite between them.
The REF pin output buffer has a non-zero output impedance; the datasheet specifies a 4.7 µF low-leakage (ceramic or tantalum) decoupling capacitor directly at REF. A 0.1 µF supply decoupling capacitor MUST be placed first as part of the REF network; if the REF cap is omitted the ADC accuracy degrades by several LSBs. For external-reference applications, the REF pin must be driven but not loaded.
Route the digital SPI traces (CS, SCLK, DOUT) on the OPPOSITE side of the ground plane from the analog input trace; the datasheet shows a clean 4-layer board with a dedicated analog ground island. Avoid running the analog input trace under or parallel to the SCLK line - the SAR converter's switched-capacitor input couples glitches through the substrate, and the trace-to-trace capacitance injects charge into AIN during transitions. Drive AIN from a low-impedance op-amp buffer (e.g. an MCP6001 or MAX4239) for >10 kHz bandwidth applications.
Choose the "+" suffix (MAX1285BCSA+) for new designs; the unmarked MAX1285BCSA carries the legacy leaded finish and may be subject to RoHS compliance restrictions in many jurisdictions. Per the order nomenclature, the "+" denotes lead-free finish without changing the electrical specifications.
Compliance Information
Verified web data does not explicitly state RoHS/REACH status for the legacy non-'+' MAX1285BCSA. The MAX1285BCSA+ / MAX1285BESA+ ordering codes (DigiKey listing reference) are lead-free; consult the manufacturer datasheet and the Analog Devices product page for final certification data.
