MAX1085ACSA+ - 10-Bit 300ksps Serial ADC | Maxim Integrated
MPN: MAX1085ACSA+ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.43 | $6.43 |
| 10 | $5.78 | $57.80 |
| 100 | $4.62 | $462.00 |
| 500 | $3.95 | $1,975.00 |
| 1,000 | $3.48 | $3,480.00 |
MAX1085ACSA+ Overview
An SAR ADC is a successive-approximation register analog-to-digital converter — a type of data converter that uses a binary-search algorithm against a precision DAC to digitize an analog input one bit per clock cycle. SAR ADCs sit in the broader hierarchy of: ADC -> data converter -> mixed-signal IC -> semiconductor. Compared with delta-sigma ADCs, SAR parts offer deterministic latency and single-shot conversions, making them preferred for multiplexed data-acquisition front-ends and control loops. Compared with flash ADCs of the same bit count, SAR parts consume far less power and silicon area.
Key features include 300 ksps maximum sampling rate (the 5 MHz clocked MAX1084 variant shares the same datasheet and pin-out at 400 ksps), 10-bit resolution, single-ended analog input, internal 2.5V reference (±1.5% initial accuracy), SPI/QSPI/MICROWIRE-compatible serial interface, 2.5 mA supply current at full speed, and automatic power-down between conversions. The 8-pin SOIC package provides a small footprint suitable for space-constrained industrial and instrumentation designs.
The MAX1085 uses a charge-redistribution DAC array with an inherent sample-and-hold front-end, allowing the analog input to settle during acquisition without an external buffer. The internal reference eliminates the need for an external reference IC, reducing BOM cost and PCB area, while still offering ±1.5% initial accuracy suitable for general-purpose 10-bit measurement.
Typical applications include portable data logging, pen-digitizer digitizing tablets, portable battery-powered instruments, isolated industrial 4-20 mA sensor digitizers, and general-purpose single-channel data acquisition. The MAX1085A grade offers specified AC electrical characteristics, while the MAX1085B grade offers slightly tighter linearity; the suffix "C" denotes the commercial 0 °C to +70 °C temperature range and "SA" denotes the 8-pin SOIC package.
When designing with the MAX1085ACSA+, place a 0.1 µF bypass capacitor within 5 mm of the AVDD pin and keep the analog input traces short and guarded. The serial interface uses SCLK, DIN, DOUT, and active-low CS — tie DIN high when reading conversions only, or hardwire it for hardware-mode operation.
Drop-in alternatives for MAX1085ACSA+ — 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 MAX1085ACSA+ (same form factor and footprint) — differing in Package, Architecture, Resolution, RoHS Status, Input Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MAX1085BCSA+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1084ACSA+
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1084BCSA
✅ Drop-In✓ In Stock
$5.18 / Unit
View Datasheet →MAX1085ACSA+T
✅ Drop-In✓ In Stock
$4.08 / Unit
View Datasheet →MAX1085ACSA+ Maximum Ratings & Electrical Characteristics
| Resolution | 10 bits |
| Sampling Rate | 300 ksps |
| Number of Channels | 1 (single-ended) |
| Input Type | Single-Ended |
| Architecture | SAR (Successive Approximation) |
| Data Interface | SPI/QSPI/MICROWIRE-compatible serial |
| Sample/Hold Ratio | 1:1 |
| Number of ADC Converters | 1 |
| Reference Type | Internal +2.5V |
| Supply Voltage | 2.7 V to 5.5 V (single supply) |
| Supply Current (Active, 300 ksps) | 2.5 mA typical |
| Supply Current (Power-Down) | < 1 µA typical |
| Operating Temperature | 0 °C to +70 °C (commercial, "C" grade) |
| Package | 8-pin SOIC (NSOIC, "SA" suffix) |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant (Pb-free "+" suffix) |
| Lead-Free | Yes |
| MSL Level | 1 (unlimited floor life at <30°C / 85% RH) |
MAX1085ACSA+ Pin Configuration
| Pin 1 | AVDD — Analog supply voltage (2.7 V to 5.5 V) |
| Pin 2 | AIN — Analog input (single-ended, 0 to VREF) |
| Pin 3 | REF — Internal +2.5 V reference output / reference input |
| Pin 4 | AGND — Analog ground |
| Pin 5 | SCLK — Serial clock input |
| Pin 6 | DOUT — Serial data output (ADC result, MSB first) |
| Pin 7 | DIN — Serial data input (tie HIGH for hardware-mode reads) |
| Pin 8 | DVDD — Digital supply voltage (2.7 V to 5.5 V) |
Typical Applications
MAX1085ACSA+ is suitable for 6 applications: Portable Data Logging, Industrial 4-20 mA Sensor Digitizing, Pen-Digitizer / Tablet Digitizing, Battery-Powered Portable Instruments, Loop-Powered Transmitter Digitizer, General-Purpose Data Acquisition Front-End.
Portable Data Logging
The MAX1085ACSA+ fits portable data-logging applications because of its 2.5 mA active supply current at 300 ksps and <1 µA automatic shutdown between conversions — its duty-cycled architecture lets average supply current scale with sample rate, so a 1 kHz logger runs well below 100 µA average. The internal +2.5 V reference eliminates the cost and quiescent current of an external reference IC, critical for battery-powered designs. The 8-pin SOIC package fits in compact handheld enclosures, and the SPI-compatible serial interface connects directly to low-power microcontrollers without glue logic.
Recommended
Industrial 4-20 mA Sensor Digitizing
Isolated 4-20 mA sensor digitizers benefit from the MAX1085ACSA+'s single-supply 2.7–5.5 V operation, internal +2.5 V reference, and small 8-pin SOIC footprint — the latter matters because isolation barriers and shunt resistors consume most of the PCB area, leaving little room for a separate reference IC. The 300 ksps throughput is more than adequate for the typical 100 Hz update rate of industrial process variables such as pressure, flow, and temperature. The SAR architecture provides single-cycle deterministic conversions, simplifying the microcontroller's averaging and smoothing algorithms on the isolated side.
Recommended
Pen-Digitizer / Tablet Digitizing
Pen-digitizer and graphics-tablet digitizing designs use the MAX1085ACSA+ because the 300 ksps sample rate captures stylus motion at high resolution (10-bit = 1024 vertical levels) while the serial output frees microcontroller I/O for the X/Y scanning matrix. The internal +2.5 V reference gives a stable full-scale conversion without requiring an external reference that would consume tablet-area budget. Single-supply 2.7–5.5 V compatibility supports both USB-powered and battery-powered tablets. The 8-pin SOIC package can be mounted near the digitizing surface with short analog traces, minimizing settling-time concerns.
Recommended
Battery-Powered Portable Instruments
Battery-powered portable instruments such as handheld multimeters, weigh scales, and field-test equipment use the MAX1085ACSA+ for its low operating power — active supply current of just 2.5 mA at 3.3 V, plus automatic shutdown dropping to <1 µA between samples, dramatically extends battery life. The single 2.7–5.5 V supply can be driven directly from a lithium-ion cell or two AA cells without level shifters. The internal +2.5 V reference removes the cost and current draw of an external precision reference IC. The 8-pin SOIC package saves PCB area for the analog front-end, signal conditioning, and isolation.
Recommended
Loop-Powered Transmitter Digitizer
Loop-powered 4-20 mA transmitters and other energy-harvesting sensors digitize their sensing element with the MAX1085ACSA+ because its <1 µA shutdown current and 2.5 mA active consumption keep total loop burden minimal while still providing 300 ksps sample rate for over-sampled measurements. The internal +2.5 V reference removes the cost and footprint of a dedicated reference IC — every square millimeter is valuable inside a 4-20 mA head-mount transmitter. The 8-pin SOIC package fits the standard small-diameter sensor housing and the single-supply 2.7–5.5 V operation interfaces directly to low-voltage loop electronics.
Recommended
General-Purpose Data Acquisition Front-End
General-purpose single-channel data-acquisition boards and break-out modules use the MAX1085ACSA+ as a compact, self-contained ADC channel — the internal +2.5 V reference, SPI-compatible serial output, and single 2.7–5.5 V supply eliminate the external analog parts (reference, charge pump, level shifters) usually needed to support a discrete ADC. The 300 ksps throughput is sufficient for audio-bandwidth (40 ksps per channel) and most industrial telemetry applications, with headroom for oversampling and averaging to improve effective resolution beyond 10 bits. The 8-pin SOIC package fits virtually any prototyping footprint including SOIC-8 breakout boards.
Recommended
Recommended Products Summary
Engineering reference data for MAX1085ACSA+ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MAX1085BCSA+ | MAX1084ACSA+ | MAX1084BCSA | MAX1085ACSA+T |
|---|---|---|---|---|---|
| Package | 8-pin SOIC (SA) | 8-pin SOIC (SA) - same | 8-pin SOIC (SA) - same | 8-pin SOIC (SA) - same | 8-pin SOIC (SA) - same |
| Brand | Analog Devices / Maxim Integrated | Analog Devices / Maxim Integrated - same | Analog Devices / Maxim Integrated - same | Analog Devices / Maxim Integrated - same | Analog Devices / Maxim Integrated - same |
| Resolution | 10 bits | 10 bits | 10 bits | 10 bits | 10 bits |
| Sampling Rate | 300 ksps | 300 ksps | 400 ksps (+33%) | 400 ksps (+33%) | 300 ksps |
| Internal Reference | +2.5 V | +2.5 V | +2.5 V | +2.5 V | +2.5 V |
| Linearity Grade | A-grade | B-grade (tighter DNL/INL) | A-grade | B-grade | A-grade |
| Architecture | SAR | SAR | SAR | SAR | SAR |
| Supply Voltage | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V |
| Operating Temperature | 0 °C to +70 °C (commercial, "C") | 0 °C to +70 °C | 0 °C to +70 °C | 0 °C to +70 °C | 0 °C to +70 °C |
Key Differentiators
- Internal +2.5V reference integrated on-chip (vs MAX1242)
- 300 ksps pin-compatible speed upgrade over MAX1242/MAX1243 (vs MAX1242)
- Automatic power-down between conversions for low average current (vs MAX1084ACSA+)
Design Notes
Place a 0.1 µF ceramic bypass capacitor within 5 mm of the AVDD pin (pin 1) and another within 5 mm of the DVDD pin (pin 8). Connect both to a clean analog ground (pin 4). AVDD and DVDD may be tied together at the device pins and driven from the same rail through an RC filter (e.g. 10 Ω + 0.1 µF + 10 µF bulk) to isolate digital switching noise from the analog supply. Keep analog input traces (pin 2 AIN) short and guarded with a ground trace to minimize capacitive coupling from digital signals.
Bypass the REF pin (pin 3) with a minimum 0.1 µF ceramic capacitor; for best 10-bit performance use 10 µF tantalum or ceramic. The internal +2.5 V reference is brought out so it can be used to drive external circuitry, but excessive loading degrades accuracy and increases noise. Route SCLK (pin 5) and DOUT (pin 6) traces away from analog traces to avoid digital-to-analog crosstalk. The DIN pin (pin 7) should be tied HIGH (to DVDD) for hardware-mode read-only operation, or driven by the microcontroller for full SPI control.
The MAX1085ACSA+ sample-and-hold has a 1:1 S/H:ADC architecture — acquisition time and conversion time are sequential. The external SCLK must idle HIGH between conversions for the SPI-compatible serial interface to function correctly; verify the host microcontroller's SPI mode configuration (CPOL=1, CPHA=0 for Mode 3). Conversion latency is one conversion cycle plus one SCLK edge to frame the output. For high-throughput designs, the MAX1084 grade at 400 ksps provides 33% more headroom with the same pinout.
Do not exceed the absolute maximum AVDD/DVDD rating of 6.0 V; the operating range is 2.7 V to 5.5 V. Tie unused digital inputs (especially DIN) to a known state — a floating DIN is a common cause of unexpected shutdown behavior. Decouple the reference pin with a real capacitor (not a ferrite or inductor) so it can source the dynamic current during conversions. Avoid drawing high AC currents from the REF pin (it is a low-current reference output). Ensure the analog input never exceeds AVDD or falls below AGND, as the ESD diodes will forward-conduct and corrupt the conversion.
Estimated: At maximum active throughput (300 ksps) and 5.5 V AVDD, the supply current is approximately 2.5 mA typical per the datasheet, so worst-case active dissipation is about 13.75 mW (P = V × I = 5.5 V × 2.5 mA). With the 8-pin SOIC package thermal resistance θJA typically around 170 °C/W (datasheet figure to verify), junction self-heating is negligible — well under 3 °C rise above ambient. Thermal management is not a concern for the MAX1085ACSA+ in any standard operating condition; focus on analog signal integrity and supply decoupling instead.
Compliance Information
RoHS-compliant and lead-free per the "+" suffix in the part number (Maxim Integrated RoHS marking convention). Not AEC-Q100 qualified — this is a commercial-grade part. For automotive applications, consult Analog Devices automotive-qualified ADC families.
