TSM1285BCSA+ - 12-Bit 300ksps SAR ADC | Silicon Labs
MPN: TSM1285BCSA+ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.5 | $6.50 |
| 10 | $5.85 | $58.50 |
| 100 | $5.2 | $520.00 |
| 500 | $4.62 | $2,310.00 |
| 1,000 | $4.1 | $4,100.00 |
TSM1285BCSA+ Overview
An SAR (Successive Approximation Register) ADC is a type of data converter that uses a binary-search algorithm against an internal DAC to digitize an analog input in N conversion clock cycles. SAR ADCs sit in the data converter hierarchy between flash converters (fast, expensive, low resolution) and sigma-delta converters (high resolution, slow, dense digital filtering). Because SAR ADCs require no continuous-time oversampling, they are well suited to multiplexed multi-channel acquisition systems, instrumentation loops, and embedded sensor readouts where deterministic latency matters more than extreme dynamic range.
Key features include 300 ksps sampling rate, single 2.7 V to 3.6 V supply operation, internal 2.5 V reference, low power consumption, and a serial interface. The serial output simplifies isolation between the analog front end and a digital host MCU or FPGA, reducing board-level pin count compared with parallel-output SAR ADCs and easing PCB routing in mixed-signal designs.
The TSM1285BCSA+ uses a charge-redistribution SAR architecture with an internal reference, internal offset calibration, and internal reference-error nulling per the manufacturer datasheet. After full-scale calibration, relative accuracy is specified against the theoretical code transfer function, supporting reliable closed-loop control and instrumentation applications where absolute transfer linearity matters.
Typical applications include portable data acquisition systems, industrial process control loops, isolated sensor front ends, motor control current/voltage sense channels, and battery-powered instrumentation. The 2nd-source SOIC-8 footprint and commercial-grade temperature rating make it a flexible part for cost-sensitive mixed-signal designs.
When designing with this ADC, ensure the analog input bandwidth does not exceed the device's -3 dB front-end limit; place a small RC anti-alias filter ahead of AIN. Decouple VDD with both bulk and 100 nF ceramic capacitance placed within 5 mm of the supply pin.
This page synthesizes distributor pricing, drop-in same-package alternatives, and practical design notes not found in the manufacturer datasheet, enabling faster part-selection decisions.
Drop-in alternatives for TSM1285BCSA+ — 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 TSM1285BCSA+ (same form factor and footprint) — differing in Package, Input Type, Internal Reference, Operating Temperature, Operating Temperature Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
TSM1285BCSA+T
✅ Drop-In✓ In Stock
$1.55 / Unit
View Datasheet →TSM1285BCSA
✅ Drop-In📋 Reference alternative (not in catalog)
MAX1285BCSA
✅ Drop-In✓ In Stock
$5.4 / Unit
View Datasheet →MAX1285BESA
✅ Drop-In✓ In Stock
$7.97 / Unit
View Datasheet →MAX1285BCSA-T
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$4.89 / Unit
View Datasheet →MAX1284BCSA
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$9.95 / Unit
View Datasheet →TSM1285BCSA+ Maximum Ratings & Electrical Characteristics
| Resolution | 12 bits |
| Sampling Rate | 300 ksps |
| Number of Inputs | 1 |
| Converter Type | SAR (Successive Approximation) |
| Architecture | Single-supply, low-power |
| Input Type | Single-ended |
| Digital Supply Voltage (VDD) | 2.7 V to 3.6 V |
| Analog Supply Voltage | 2.7 V to 3.6 V |
| Internal Reference Voltage | 2.5 V (internal) |
| Data Interface | Serial |
| Operating Temperature | -40C to +85C |
| Temperature Grade | Commercial |
| Package / Supplier Device Package | 8-SOIC (SOP, 8-pin) |
| Mounting Type | Surface Mount |
| Terminal Form | Gull Wing |
| Manufacturer | Silicon Labs (orig. Touchstone Semiconductor) |
TSM1285BCSA+ Pin Configuration
| Pin 1 | VDD — Power supply input (2.7 V to 3.6 V) |
| Pin 2 | GND — Ground return for analog and digital domains |
| Pin 3 | REF — Internal 2.5 V reference output / reference bypass node |
| Pin 4 | AIN — Analog input (single-ended, 0 V to VREF range) |
| Pin 5 | GND — Ground (digital return tie-point) |
| Pin 6 | /CS — Active-low chip select for serial interface |
| Pin 7 | SCLK — Serial interface clock input |
| Pin 8 | DOUT — Serial data output (12-bit conversion result) |
Typical Applications
TSM1285BCSA+ is suitable for 6 applications: Portable Data Acquisition Systems, Industrial Process Control Loops, Isolated Sensor Front Ends, Motor Control Current and Voltage Sense, Battery-Powered Instrumentation, Embedded Mixed-Signal MCU Boards.
Portable Data Acquisition Systems
The TSM1285BCSA+ is well matched to portable battery-powered data acquisition front ends where its single-supply 2.7 V to 3.6 V operation, internal 2.5 V reference, and 300 ksps throughput provide a compact, low-BOM digitizer for sensor signals. Designers can stream up to 300,000 samples per second over the serial SPI-like interface to an MCU while drawing low quiescent current, enabling handheld multimeters and USB-connected sensor pods that run for hours on a single cell. The SOIC-8 footprint keeps the analog section under 30 mm² on a 4-layer board, and the internal reference eliminates external reference drift and warm-up error.
Recommended
Industrial Process Control Loops
For industrial process control loops (4-20 mA current loops, RTD conditioning boards, weigh scale front ends), the TSM1285BCSA+ provides deterministic single-shot conversion latency thanks to its SAR architecture, with throughput of 300 ksps far faster than typical loop update rates. The internal 2.5 V reference nullifies reference errors during factory calibration, while the commercial -40C to +85C operating range covers most factory-floor enclosures. The serial interface is robust against ground-shift noise between the isolated analog front end and the digital MCU, and the SOIC-8 footprint simplifies EMC shielding on a small island.
Recommended
Isolated Sensor Front Ends
In isolated sensor modules reading thermocouples, strain gauges, or shunt currents, the TSM1285BCSA+ serial output minimizes the number of signals that must cross the digital isolator - typically just SCLK, DOUT, and /CS - reducing isolator channel count from 8-12 down to 3 and shrinking both BOM cost and quiescent current. The 300 ksps throughput supports oversampling at the sensor front end, while the SOIC-8 footprint and single 3.3 V supply play well with low-power isolated DC/DC topologies. Designers using digital isolators like the MAX1295ACEI or its lower-channel counterpart benefit from this reduced channel count.
Recommended
Motor Control Current and Voltage Sense
Brushless DC (BLDC) and stepper motor control boards require simultaneous sampling of phase currents and bus voltage at 10-50 kHz per channel to close the current loop cleanly. The TSM1285BCSA+ provides up to 300 ksps throughput via its serial interface, suitable for multiplexing 2-3 low-side shunt currents through a single ADC and a small front-end mux. The internal 2.5 V reference and single 3.3 V supply reduce BOM and PCB area around the power-stage heatsink, while its commercial-grade temperature rating supports most commercial motor-control enclosures. For systems needing simultaneous sampling, two TSM1285BCSA+ parts can be synchronized via a shared /CS line.
Recommended
Battery-Powered Instrumentation
The TSM1285BCSA+ is purpose-built for low-power battery-driven instrumentation such as handheld multimeters, portable environmental loggers, and field data acquisition pods. Its single-supply 2.7 V to 3.6 V operation lets it share a Li-Ion cell or two AA cells with the host MCU without additional LDO overhead, and the internal 2.5 V reference removes the extra quiescent draw of an external reference IC. The SOIC-8 package fits inside compact handheld enclosures, and the 300 ksps throughput covers oversampled sensor acquisition with margin to spare.
Recommended
Embedded Mixed-Signal MCU Boards
Many microcontroller and DSP-based designs need a separate analog-to-digital converter because the internal MCU ADC is multiplexed across many channels or limited in throughput. The TSM1285BCSA+ fills this role well: 12 bits at 300 ksps over a 3-wire SPI serial interface that any 3.3 V-tolerant GPIO can drive. Its SOIC-8 footprint occupies a tiny island of analog ground next to the MCU's digital plane, and the single 3.3 V supply simplifies power-tree design. Designers evaluating MCU companion ADCs will find the TSM1285BCSA+ an excellent choice over most MCU-built-in ADCs when channel count and accuracy matter.
Recommended
Recommended Products Summary
Engineering reference data for TSM1285BCSA+ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TSM1285BCSA+T | TSM1285BCSA | MAX1285BCSA | MAX1285BESA | MAX1285BCSA-T |
|---|---|---|---|---|---|---|
| Package | 8-SOIC | 8-SOIC - identical | 8-SOIC - identical | 8-SOIC - identical | 8-SOIC - identical | 8-SOIC - identical |
| Brand | Silicon Labs | Silicon Labs | Silicon Labs | Maxim Integrated | Maxim Integrated | Maxim Integrated |
| Resolution | 12 bits | 12 bits | 12 bits | 12 bits | 12 bits | 12 bits |
| Sampling Rate | 300 ksps | 300 ksps | 300 ksps | 300 ksps | 300 ksps | 300 ksps |
| 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 | 2.7 V to 3.6 V | 2.7 V to 3.6 V |
| Internal Reference | 2.5 V internal | 2.5 V internal | 2.5 V internal | 2.5 V internal | 2.5 V internal | 2.5 V internal |
| Data Interface | Serial (SPI-like) | Serial (SPI-like) | Serial (SPI-like) | Serial (SPI-like) | Serial (SPI-like) | Serial (SPI-like) |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
Key Differentiators
- Single-supply operation with internal reference (vs MAX1285BCSA)
- Commercial temperature rating across same package (vs MAX1285BESA)
- Compact SOIC-8 footprint with internal 2.5V reference (vs MAX1284BCSA)
Design Notes
Decouple VDD with both a 1 uF to 10 uF bulk ceramic capacitor and a 100 nF high-frequency ceramic cap placed within 5 mm of the VDD pin. The 100 nF cap supplies the transient current step during the SAR conversion acquisition phase; without it, VDD droop can couple directly into the analog input path and degrade linearity. The bulk capacitor handles low-frequency drift and should sit on the supply plane near the analog ground stitch via. Tie GND pins to a single, low-impedance analog ground island with one stitch to the digital ground at the MCU.
Route the serial interface (SCLK, DOUT, /CS) on the digital side of the ground plane, perpendicular to and away from the analog input trace. Keep the AIN trace short and surrounded by analog ground guard rings to minimize digital noise coupling into the 12-bit front end. Place an anti-alias filter (typically 100 ohm and 1 nF forming an RC) within 5 mm of the AIN pin. Avoid running digital traces parallel to AIN on the same layer; if they must cross, do so at 90 degrees to minimize coupling area.
Do not apply an analog input beyond the supply rails; the TSM1285BCSA+ is designed for input voltages from 0 V to VREF, and exceeding this range can permanently damage the input ESD structure. The internal reference requires a 1 uF (or larger) bypass capacitor close to the REF pin to maintain reference stability; missing this capacitor degrades INL and DNL. For multi-channel-multiplexed applications, ensure the MUX settles below 1 LSB within the acquisition window before /CS goes high.
Because the TSM1285BCSA+ uses an SAR core, its input current demand is non-linear: the input presents a brief surge during the acquisition phase (when the internal sampling capacitor is connected to AIN) and then settles to negligible current during conversion. Source impedance above 1 kohm introduces gain error and degrades INL at full throughput; add a wide-bandwidth op-amp buffer if the source exceeds 1 kohm. Series ferrite beads on VDD can resonate with the 100 nF ceramic bypass and amplify LSB jitter; if used, place damping across the bead.
Compliance Information
RoHS compliant and lead-free per manufacturer datasheet (Touchstone / Silicon Labs). REACH and halogen-free status not explicitly stated in the provided data; AEC-Q100 not applicable for commercial-temperature mixed-signal ADC.
