TSM1285BCSA+T - 12-Bit 300ksps SAR ADC w/ 2.5V Ref | Silicon Labs
MPN: TSM1285BCSA+T ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.42 | $3.42 |
| 10 | $3.07 | $30.70 |
| 100 | $2.61 | $261.00 |
| 500 | $2.21 | $1,105.00 |
| 1,000 | $1.84 | $1,840.00 |
| 3,000 | $1.55 | $4,650.00 |
TSM1285BCSA+T Overview
A SAR ADC is a precision data-acquisition converter that uses a binary search algorithm and an internal capacitive DAC to compare the sampled input against a reference voltage. It is a sub-category of analog-to-digital converters (ADC), itself a subclass of data-converter ICs within mixed-signal semiconductor devices. SAR ADCs are valued for their deterministic latency (no pipeline delay), low power consumption, and excellent DC accuracy, making them the standard choice for multiplexed data-acquisition systems, instrumentation, and sensor signal chains.
Key features include ±1 LSB INL (max) typical linearity, an internal track-and-hold capable of handling input bandwidths up to several MHz, a low conversion-mode power dissipation below 2.5 mA, and a power-down mode that drops quiescent current to microamp levels for battery-powered designs. The serial interface is SPI-/QSPI-/MICROWIRE-compatible, allowing direct connection to most microcontrollers and DSPs without glue logic.
Architecturally, the TSM1285BCSA+T combines a high-bandwidth track-and-hold, a charge-redistribution SAR core clocked from an internal oscillator, a low-drift buried-Zener reference (trimmed to ±2%), and a low-noise input buffer. The integrated reference removes a common BOM line, saving PCB area and lowering system cost in precision designs.
Typical applications include portable instrumentation and data loggers, pen-digitizers and tablet input systems, loop-powered 4-20 mA sensor digitizers, factory-automation sensor front ends, and battery-monitoring modules for portable equipment.
Designers should note that the SHDN pin must be driven logic-high for normal conversion and pulled logic-low for power-down. The internal reference output (REF) requires a 2.2 µF minimum bypass capacitor; values lower than this degrade linearity. Input signals must remain within 0 V to VREF to avoid saturation.
This page synthesizes distributor pricing, pin-compatible drop-in alternatives including the Maxim MAX1285BCSA family, and practical design notes that are not consolidated in the manufacturer datasheet, supporting faster component evaluation.
Drop-in alternatives for TSM1285BCSA+T — 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+T (same form factor and footprint) — differing in Package, Input Type, Operating Temperature, Resolution, Internal Reference Voltage.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
TSM1285BCSA+
✅ Drop-In✓ In Stock
$4.1 / Unit
View Datasheet →MAX1285BCSA
✅ Drop-In✓ In Stock
$5.4 / Unit
View Datasheet →MAX1285BESA
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$7.97 / Unit
View Datasheet →MAX1284BCSA
✅ Drop-In✓ In Stock
$9.95 / Unit
View Datasheet →MAX1285BCSA-T
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$4.89 / Unit
View Datasheet →TSM1285BCSA+T Maximum Ratings & Electrical Characteristics
| Resolution | 12 bits |
| Number of Channels | 1 single-ended input |
| Converter Architecture | SAR (Successive Approximation Register) |
| Sampling Rate | 300 ksps |
| Supply Voltage | +2.7 V to +3.6 V (single supply) |
| Supply Current at 300 ksps | < 2.5 mA (typical) |
| Internal Reference Voltage | +2.5 V |
| External Reference Range | 0 V to AVDD |
| Input Voltage Range | 0 V to VREF (single-ended) |
| Digital Interface | SPI / QSPI / MICROWIRE-compatible serial |
| Package | 8-pin SOIC (0.154 inch / 3.90 mm width) |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited) |
| RoHS Status | Compliant |
TSM1285BCSA+T Pin Configuration
| Pin 1 | REF — Reference voltage input/output (internal +2.5V); bypass with 2.2µF minimum |
| Pin 2 | AVDD — Analog supply voltage (+2.7V to +3.6V) |
| Pin 3 | AIN — Analog input (single-ended, 0V to VREF) |
| Pin 4 | GND — Analog and digital ground |
| Pin 5 | SHDN — Shutdown input, active low (logic low = power-down) |
| Pin 6 | DOUT — Serial data output (SPI MISO) |
| Pin 7 | SCLK/DIN — Serial clock / serial data input depending on mode |
| Pin 8 | CS — Chip select (active low) for SPI frame control |
Typical Applications
TSM1285BCSA+T is suitable for 6 applications: Portable Data Acquisition / Data Loggers, Industrial 4-20 mA Sensor Digitizer, Battery Monitoring in Portable Equipment, Pen Digitizer / Tablet Input Systems, Factory Automation Sensor Front End, Loop-Powered Field Transmitter.
Portable Data Acquisition / Data Loggers
The TSM1285BCSA+T fits portable data-logger designs because its 300 ksps throughput digitizes multi-channel sensor streams via an external mux without pipeline delay, while its <2.5 mA supply current at full rate preserves battery life. The internal +2.5 V reference eliminates a separate reference IC, reducing BOM cost and PCB area, and the SHDN pin drops quiescent current to the µA range between conversions. With single +2.7 V to +3.6 V supply operation, the part runs directly from a single Li-ion cell. Designed alongside companion MPNs: an external 4-channel MUX (e.g., MAX4051) and a low-power MCU like the Silicon Labs EFM32 or Microchip PIC16 for housekeeping. Reference the manufacturer datasheet typical application circuit for input-protection guidance.
Recommended
Industrial 4-20 mA Sensor Digitizer
In 4-20 mA loop-powered sensor front ends, the TSM1285BCSA+T digitizes the loop voltage after a 250 Ω precision sense resistor, producing a digital reading proportional to current. The 12-bit resolution yields ~0.6 µA per LSB (at full scale = 24 mA / 4096 LSB), adequate for most industrial sensor spans, and the integrated +2.5 V reference stabilizes calibration against supply variation. The single-ended input accepts 0 V to VREF directly when the loop voltage is level-shifted into the ADC input band. Pairing with a low-noise precision op-amp as an input buffer improves ESD/surge immunity. The 8-SOIC footprint is footprint-compatible with Maxim MAX1285BCSA for second-source qualification on industrial BOMs.
Recommended
Battery Monitoring in Portable Equipment
Battery-monitoring modules in portable medical or test equipment benefit from the TSM1285BCSA+T's low conversion-mode power (<2.5 mA) and microamp-range shutdown current, extending runtime in always-on systems. The internal 2.5 V reference anchors accurate cell-voltage measurement up to ~10 V when the input is resistively divided, and the SPI-compatible serial interface streams conversions directly to the host MCU at up to 300 ksps. The 8-pin SOIC provides a low-profile solution for stacked Li-ion packs. Reference design consideration: place a 2.2 µF ceramic bypass on REF and keep analog/digital grounds stitched under the package per the datasheet layout guidance.
Recommended
Pen Digitizer / Tablet Input Systems
Pen-digitizer and tablet input systems rely on continuous analog sampling of stylus-position signals, and the TSM1285BCSA+T's 300 ksps throughput supports >100 kHz signal bandwidth for smooth cursor tracking. The SAR architecture introduces zero pipeline delay, providing instantaneous position feedback with no algorithmic correction, which is critical for natural handwriting latency. The single +3.3 V supply runs directly from tablet battery rails. The compact 8-SOIC footprint fits the dense PCBs of modern tablets and pen displays. The internal reference removes a precision analog IC from the BOM, lowering bill-of-materials cost.
Recommended
Factory Automation Sensor Front End
Factory-automation sensor front ends digitize temperature, pressure, and flow transducer outputs at moderate rates with deterministic latency. The TSM1285BCSA+T's SAR architecture delivers single-cycle conversion with no pipeline delay, ideal for closed-loop control loops where deterministic sample latency is required. The 0 V to VREF single-ended input accepts thermocouple-amplified or bridge-amplified signals when appropriately conditioned. The internal 2.5 V reference stabilizes readings against supply variation common in 24 V industrial backplanes. The 8-SOIC footprint is industry-standard, simplifying PCB layout in industrial controllers. The SHDN pin enables sub-microamp standby for energy-managed sensor nodes.
Recommended
Loop-Powered Field Transmitter
Loop-powered 4-20 mA field transmitters digitize sensor outputs and encode them back onto the loop. The TSM1285BCSA+T's <2.5 mA supply current at 300 ksps leaves budget for the rest of the transmitter (MCU, sensor excitation, isolated interface) under the 4 mA zero-scale loop budget. The integrated +2.5 V reference removes an external reference IC, saving BOM cost and PCB area in space-constrained field-mounted enclosures. The SPI-compatible serial interface allows easy MCU integration. The 8-pin SOIC is footprint-compatible with Maxim MAX1285BCSA, supporting second-source qualification for hazardous-location certifications. Reference the manufacturer datasheet for loop-isolation circuit examples.
Recommended
Recommended Products Summary
Engineering reference data for TSM1285BCSA+T — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TSM1285BCSA+ | MAX1285BCSA | MAX1285BESA | MAX1284BCSA | MAX1285BCSA-T |
|---|---|---|---|---|---|---|
| Brand | Silicon Labs | Silicon Labs | Maxim Integrated | Maxim Integrated | Maxim Integrated | Maxim Integrated |
| Package | 8-SOIC (0.154 inch) | 8-SOIC (0.154 inch) - same | 8-SOIC (0.154 inch) - same | 8-SOIC (0.150 inch ext-temp) - same footprint | 8-SOIC (0.154 inch) - same | 8-SOIC (0.154 inch) - same |
| 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 |
| Internal Reference | +2.5 V | +2.5 V | +2.5 V | +2.5 V | +2.048 V | +2.5 V |
| 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 |
| Serial Interface | SPI/QSPI/MICROWIRE | SPI/QSPI/MICROWIRE | SPI/QSPI/MICROWIRE | SPI/QSPI/MICROWIRE | SPI/QSPI/MICROWIRE | SPI/QSPI/MICROWIRE |
| Shutdown Pin | Yes (active low) | Yes (active low) | Yes (active low) | Yes (active low) | Yes (active low) | Yes (active low) |
Key Differentiators
- Internal +2.5 V reference integrated (vs MAX1284BCSA)
- Silicon Labs primary-source qualification (vs MAX1285BCSA)
- Tape-and-reel orientation suffix (+T) (vs TSM1285BCSA+)
Design Notes
Place the 2.2 µF REF bypass capacitor as close to pin 1 (REF) as possible with a wide, short trace to AVDD; values below 2.2 µF degrade linearity per the Silicon Labs datasheet. Keep analog input traces short and guarded by a ground pour to minimize digital noise pickup. Place a 0.1 µF ceramic bypass within 3 mm of AVDD (pin 2) in parallel with a 10 µF bulk capacitor; insufficient decoupling causes conversion-noise spikes that show up as missing codes.
Estimated: at AVDD=3.3V and 300 ksps continuous sampling, the TSM1285BCSA+T draws approximately 2.5 mA (per datasheet), or about 8.25 mW. For battery-powered applications, drive SHDN low between conversions to drop quiescent current to the µA range; the wake-up time from SHDN is specified in the datasheet timing section and must be respected before initiating a conversion. A series ferrite bead on AVDD plus a bulk capacitor reduces supply-borne noise coupling from digital circuits on the same rail.
Common pitfalls: (1) Driving AIN above AVDD or below GND causes ESD-style latchup; add a clamp diode or buffer op-amp if the source can exceed the rails. (2) Forgetting the 2.2 µF REF bypass degrades INL by several LSB. (3) Operating with CS floating or tied high produces indeterminate behavior; tie CS to a valid MCU GPIO and never leave it floating. (4) Sampling faster than the input RC bandwidth allows causes gain error; add a small RC anti-alias filter on AIN. (5) Digital activity on SCLK/DIN during conversion may couple into the analog front end; gate SCLK around the conversion complete signal.
Split analog and digital ground planes if the PCB has noisy digital circuitry on the same board, joining them only at a single point near the ADC GND pin (pin 4). Route SPI traces (SCLK, DOUT, CS) on the digital side of the partition and the analog input traces (AIN, REF) on the analog side. Keep the analog input trace away from switching power inductors or high-frequency clocks. A 4-layer PCB with a dedicated ground plane is strongly recommended for designs targeting the datasheet's full 12-bit linearity.
Compliance Information
RoHS compliant per Silicon Labs product page. Not AEC-Q100 qualified (commercial/industrial target). Lead-free reflow compatible.
