AT21CS01-STUM16-T - 1Kb Single-Wire EEPROM, SOT-23-3 | Microchip
MPN: AT21CS01-STUM16-T ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.79 | $0.79 |
| 10 | $0.74 | $7.40 |
| 100 | $0.62 | $62.00 |
| 500 | $0.55 | $275.00 |
| 1,000 | $0.48 | $480.00 |
AT21CS01-STUM16-T Overview
Background Knowledge: A Single-Wire EEPROM (also called SEEPROM or UNI/O EEPROM) is a non-volatile serial memory that uses a single bidirectional data line plus ground for both power and communication. In the broader memory taxonomy, single-wire EEPROM belongs to EEPROM -> non-volatile memory (NVM) -> semiconductor memory -> integrated circuit. Its single-pin interface makes it ideal where PCB real estate is at a premium and only two mechanical contacts are practical, such as cable-terminated cartridges or disposable probes.
Key features include more than one million write-cycle endurance per memory location, self-timed erase-and-write cycles of 5 ms maximum, low-power CMOS technology drawing only 1 mA active and sub-microamp standby, and a compact 3-pin SOT-23 package. The factory-locked 64-bit serial number is laser-programmed at production and is read-only, providing a globally unique identifier. Optional 128-bit user memory allows field customization.
The architecture uses a single-wire command layer that mirrors I2C-style addressing: a START condition, device address byte, ACK, memory address, and data payload terminated by a STOP condition. The internal charge pump generates the 9V to 12V needed to erase and program the floating-gate cells, while the wide 1.7V to 3.6V bus voltage range enables direct connection to 1.8V, 2.5V, 3.0V, and 3.3V host microcontrollers without level shifters.
Typical applications include analog sensor calibration data storage, ink and toner printer cartridge identification, after-market consumable authentication, medical disposable accessory tracking, e-meter tamper-detection records, and small-form-factor cable ID tags. The single-wire interface eliminates the need for an extra signal line, allowing two mechanical contact points to deliver both power and bidirectional data.
A primary design consideration is that the host must source a 1.7V-3.6V pull-up on SI/O; no separate VCC pin is provided. The 5 ms maximum write cycle means page-mode writes are not supported - each byte write requires its own 5 ms window. Finally, the unique serial number is read using a dedicated security-register command, not through the main memory array.
This page synthesizes the Microchip datasheet DS20005857D specifications, distributor pricing tiers, and application context for the AT21CS01-STUM16-T to assist design engineers with single-wire EEPROM selection, drop-in alternatives, and unpowered-attachment system design.
Drop-in alternatives for AT21CS01-STUM16-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 AT21CS01-STUM16-T (same form factor and footprint) — differing in Interface, Memory Type, Package, Write Endurance.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AT21CS01-STUM10-T
✅ Drop-In✓ In Stock
$0.26 / Unit
View Datasheet →AT21CS01-SSHM16-T
✅ Drop-In📋 Reference alternative (not in catalog)
AT21CS11-STUM10-T
✅ Drop-In📋 Reference alternative (not in catalog)
AT21CS11-SSHM16-T
✅ Drop-In📋 Reference alternative (not in catalog)
AT21CS01-STUM16-T Specifications
| Memory Type | Single-Wire EEPROM (SEEPROM) |
| Memory Density | 1 Kbit (128 x 8) |
| Interface | Single Wire (UNI/O), compatible with I2C-style framing |
| Clock Frequency (Max) | 125 kHz (high-speed mode) |
| Standard-Speed Mode | 15.4 kbps |
| Operating Voltage | 1.7 V to 3.6 V (SI/O pull-up) |
| Write Cycle Time (Max) | 5 ms |
| Write Endurance | >1,000,000 cycles per memory location |
| Unique Serial Number | 64-bit, factory-programmed, read-only |
| Security Register | 256-bit (64-bit unique ID + 128-bit user-programmable + 64-bit reserved) |
| Package | SOT-23-3 (3-pin) |
| Mounting Type | Surface Mount |
| Operating Temperature | -40 C to +85 C (industrial) |
| MSL Level | 1 |
| RoHS Status | Compliant |
| Lead-Free | Yes |
| Manufacturer | Microchip Technology |
AT21CS01-STUM16-T Pin Configuration
| Pin 1 | SI/O — Single-wire serial data and power input/output |
| Pin 2 | NC — No internal connection (leave floating) |
| Pin 3 | GND — Ground reference |
Typical Applications
AT21CS01-STUM16-T is suitable for 6 applications: Analog Sensor Calibration Data Storage, Ink and Toner Printer Cartridge Identification, Medical Disposable Accessory Tracking, After-Market Consumable Authentication, Electronic Meter Tamper-Detection Records, Small-Form-Factor Cable ID Tags.
Analog Sensor Calibration Data Storage
The AT21CS01-STUM16-T is purpose-built for analog sensor calibration storage because the single-wire UNI/O protocol requires only two mechanical contacts - SI/O and GND - while still delivering 1 Kbit of non-volatile memory plus a factory-locked 64-bit unique serial number. In a typical analog sensor probe, the EEPROM sits at the tip, and the host MCU provides a 1.7V-3.6V pull-up on the SI/O pin during read/write. The 1M+ write endurance per location allows repeated recalibration events across the sensor's service life, while the 5 ms write cycle is acceptable for low-frequency calibration updates that happen at factory build or during scheduled recalibration. The unique serial number also supports traceability back to the calibration fixture and date code.
Recommended
Ink and Toner Printer Cartridge Identification
In printer cartridge applications, the AT21CS01-STUM16-T identifies the cartridge type, fill level, and consumable authenticity through its factory-programmed 64-bit unique serial number and user-programmable 128-bit security register. The single-wire interface is critical because the cartridge PCB typically has only two spring contacts mating to the printer, and adding an extra I2C line would mechanically complicate the contact pad. The device operates from 1.7V to 3.6V, directly compatible with the printer's 3.3V logic rail, and its 1M+ write endurance tolerates daily page-count updates over the cartridge's full life. The 5 ms write cycle is invisible at human time scales, so the printer's update algorithm treats it as instantaneous.
Recommended
Medical Disposable Accessory Tracking
In medical disposable accessories such as single-use probe covers, biopsy needle guides, and infusion set reservoirs, the AT21CS01-STUM16-T provides single-use authentication and lot tracking. The factory-locked 64-bit serial number guarantees that each disposable accessory is uniquely identifiable, supporting FDA UDI (Unique Device Identification) requirements. The single-wire UNI/O protocol enables the host medical device to power and communicate through just two contact pads on the disposable, which is essential for cost-sensitive single-use items. The -40C to +85C industrial temperature range accommodates cold-chain storage and body-temperature operation. Because the unique serial number is laser-programmed and read-only, it cannot be counterfeited or reused, supporting anti-counterfeit protocols in regulated medical markets.
Recommended
After-Market Consumable Authentication
The AT21CS01-STUM16-T secures after-market consumables in industrial tools, appliances, and 3D-printing filament cartridges by storing a cryptographic challenge or usage counter in its 128-bit user-programmable memory area. The host system reads the factory-locked 64-bit unique serial number to verify the cartridge is genuine, then writes/reads the 128-bit user area to track usage cycles or expiration state. Because the UNI/O protocol is proprietary to Microchip, competitors cannot easily clone the consumable, giving OEMs an authentication advantage. The SOT-23-3 package measures approximately 2.9 mm x 1.3 mm, fitting comfortably inside small-form-factor consumable housings. The 1.7V-3.6V supply is parasitically drawn through SI/O, so the consumable does not need a separate power line.
Recommended
Electronic Meter Tamper-Detection Records
Utility meters (water, gas, electricity) use the AT21CS01-STUM16-T to log tamper events, firmware revision, and calibration constants in a non-volatile memory that survives power disconnection. The factory-programmed 64-bit unique serial number uniquely identifies each meter for billing and audit purposes, while the 1M+ write endurance supports daily tamper-log writes over the meter's 20+ year service life. The single-wire UNI/O interface simplifies the meter's internal wiring harness: only two wires run between the meter's main board and any peripheral sensor that needs identity storage. The 1.7V-3.6V range is compatible with both 3.3V and 2.5V host MCUs commonly used in metering applications.
Recommended
Small-Form-Factor Cable ID Tags
Cable assemblies and breakout harnesses often need a memory tag at one end to identify the cable revision, length, calibration data, or test fixture origin. The AT21CS01-STUM16-T enables this through its SOT-23-3 footprint that fits inside the cable overmold or connector backshell, using only two wires (SI/O and GND) embedded in the cable. The factory-locked 64-bit unique serial number gives every cable a globally unique ID, while the user-programmable 128-bit area can store cable-specific calibration or test data. Because the protocol is single-wire UNI/O, the host tester does not need a dedicated I2C port - a single GPIO with bit-bang firmware is sufficient, reducing tester cost and complexity.
Recommended
Recommended Products Summary
Engineering reference data for AT21CS01-STUM16-T — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AT21CS01-STUM10-T | AT21CS01-SSHM16-T | AT21CS11-STUM10-T | AT21CS11-SSHM16-T |
|---|---|---|---|---|---|
| Package | SOT-23-3 | SOT-23-3 | SOIC-8 | SOT-23-3 | SOIC-8 |
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Memory Density | 1 Kbit (128 x 8) | 1 Kbit (128 x 8) | 1 Kbit (128 x 8) | 1 Kbit (128 x 8) | 1 Kbit (128 x 8) |
| Interface Protocol | Single-Wire UNI/O | Single-Wire UNI/O | Single-Wire UNI/O | I2C (2-wire) | I2C (2-wire) |
| Operating Voltage | 1.7 V to 3.6 V | 1.7 V to 3.6 V | 1.7 V to 3.6 V | 1.7 V to 3.6 V | 1.7 V to 3.6 V |
| Max Clock Frequency | 125 kHz | 125 kHz | 125 kHz | 400 kHz (I2C) | 400 kHz (I2C) |
| Write Endurance | >1,000,000 cycles | >1,000,000 cycles | >1,000,000 cycles | >1,000,000 cycles | >1,000,000 cycles |
| Unique 64-bit Serial Number | Yes (factory-programmed) | Yes (factory-programmed) | Yes (factory-programmed) | Yes (factory-programmed) | Yes (factory-programmed) |
| Write Cycle Time (Max) | 5 ms | 5 ms | 5 ms | 5 ms | 5 ms |
Key Differentiators
- Single-wire UNI/O protocol with unique 64-bit serial number (vs AT21CS11-STUM10-T (I2C version))
- SOT-23-3 footprint for ultra-compact designs (vs AT21CS01-SSHM16-T (SOIC-8))
- Tape-and-reel STUM16 orientation for high-volume assembly (vs AT21CS01-STUM10-T)
Design Notes
Because the SOT-23-3 package has only three pins, layout is critical: route SI/O directly to the host GPIO with a 1.7V-3.6V pull-up resistor (typically 4.7 kohm to 10 kohm) and place the decoupling capacitor (100 nF typical) within 5 mm of the SI/O pin. Pin 2 (NC) MUST be left floating per Microchip datasheet DS20005857D - do NOT connect it to GND or VCC, as this can cause internal latch-up. Route SI/O away from high-frequency switching signals to prevent capacitive coupling that would disrupt the single-wire protocol timing.
Do NOT attempt to communicate with the AT21CS01-STUM16-T using standard I2C commands - the UNI/O single-wire protocol uses a custom command set (START, device address, ACK, memory address, data, STOP) with timing parameters that differ from I2C. Bit-banging I2C will not work. Use Microchip's AN-352 application note or the official UNI/O driver library. Also note that the device does NOT support page writes - each byte requires its own 5 ms commit window, so do not expect I2C-like sequential write performance.
The AT21CS01-STUM16-T draws its supply entirely through the SI/O pull-up; there is no separate VCC pin. The host MCU must actively drive SI/O high during idle to maintain the 1.7V-3.6V supply rail, and during communication the device pulls SI/O low for ACK and data bits. Estimated standby current is sub-microampere and active read current is approximately 1 mA, per the Microchip datasheet. If the host cannot continuously hold SI/O high, the device may brown out and lose communication; in such cases, add an external hold circuit or capacitor reservoir.
The single-wire UNI/O protocol runs at 15.4 kbps standard or 125 kbps high-speed, with strict timing tolerances. At 125 kbps, total bit period is 8 us with sub-microsecond setup/hold requirements. Keep the SI/O trace under 50 mm and avoid stubs or branches; if longer traces are unavoidable, use a series resistor (100 ohm) near the host GPIO to dampen reflections. Do NOT put the AT21CS01-STUM16-T on a shared bus with I2C devices unless the host GPIO is dedicated, as protocol collisions can corrupt both buses.
Compliance Information
RoHS and REACH compliant per Microchip product page. Halogen-free per Microchip environmental compliance documentation. Not AEC-Q100 qualified - this is a commercial/industrial grade part; the AT21CS01 family does not offer automotive-qualified variants.
