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STMicroelectronics SR2UABU
- Part No.:
- SR2UABU
- Manufacturer:
- STMicroelectronics
- Category:
- Supervisors
- Package:
- 6-UDFN
- Datasheet:
-
SR2UABU.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 6UDFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,000
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Product details
Overview
SR2UABU from STMicroelectronics is a 6-pin Smart Reset™ supervisor IC designed for ultra-low-power wearable systems requiring dual-button controlled, extended-delay reset initiation. It operates from 1.65 V to 5.5 V, draws only 1.5 µA typical supply current, and provides factory-programmed 10 s Smart Reset™ setup delay (tSRC) and 360 ms fixed reset pulse duration (tREC), with active-low open-drain RST output and internal pull-up resistor option.
For engineers reviewing the SR2UABU datasheet, SR2UABU pinout, SR2UABU application, or SR2UABU equivalent, this device addresses critical requirements in compact, battery-constrained systems where inadvertent short-press resets must be rejected while enabling reliable hard-reset recovery via sustained dual-button press - especially relevant for activity tracker firmware recovery, smartwatch system initialization, and wearable MCU watchdog coordination.
Technical Context
The SR2UABU implements a dual-input, synchronized Smart Reset™ architecture: both SR0 and SR1 inputs must be held low simultaneously for the full factory-set tSRC = 10 s (typ.) before asserting RST; no power-on reset is generated. Its test mode is triggered by overvoltage on SR0 (VCC + 0.9–1.4 V), initiating a shortened 21 ms tSRC-SHORT for rapid validation.
Reset output behavior is deterministic and option-specific: RST remains asserted for exactly tREC = 360 ms (typ.), independent of input release timing, ensuring consistent MCU reset hold time. Input logic thresholds are fixed (VIL ≤ 0.3 V, VIH ≥ 0.85 × VCC), and undervoltage lockout deasserts RST below 1.575 V (typ.), maintaining valid output states down to VCC = 1.0 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply voltage range | 1.65 V to 5.5 V - supports single-cell Li-ion, coin cell, and multi-rail embedded systems without external regulation |
| Supply current (typ.) | 1.5 µA at VCC = 5.0 V - enables >1-year battery life in always-on wearable applications |
| Smart Reset™ delay (tSRC) | 10.0 s (factory-programmed, ±20% over -40°C to +85°C) - rejects accidental presses while enabling deliberate system recovery |
| Reset pulse duration (tREC) | 360 ms (factory-programmed, ±33%) - guarantees sufficient MCU reset hold time regardless of button release timing |
| Input logic levels | VIL ≤ 0.3 V, VIH ≥ 0.85 × VCC - ensures robust noise immunity and compatibility with 1.8 V/3.3 V/5 V GPIOs |
| Operating temperature | -40 °C to +85 °C - qualified for consumer wearable environments including skin-contact devices |
| Package | UDFN6 (1.6 mm × 1.3 mm × 0.55 mm, 0.4 mm pitch) - enables placement in space-constrained PCB footprints |
Pinout & Package
SR2UABU is housed in a 6-pin UDFN package (1.6 mm × 1.3 mm, 0.4 mm pitch), ECOPACK®2-compliant, with exposed thermal pad not connected internally. Pin 1 is marked by a dot; Pin 4 is NC (not bonded).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VSS | Supply ground | Reference return path for all internal circuitry; must be low-impedance connection to system GND plane |
| 2 SR1 | Secondary Smart Reset™ input | Active-low push-button input; requires external pull-up if internal option disabled; must be held low concurrently with SR0 for tSRC |
| 3 RST | Reset output | Active-low open-drain output with optional internal pull-up; asserts for fixed 360 ms after tSRC timeout |
| 4 NC | No connect | Not bonded; must be connected to VSS per layout guidelines to ensure mechanical stability and thermal performance |
| 5 SR0 | Primary Smart Reset™ input | Active-low push-button input with test-mode trigger capability (VCC + 0.9–1.4 V); initiates tSRC-SHORT when grounded in test mode |
| 6 VCC | Supply voltage | 1.65–5.5 V input; requires 0.1 µF ceramic decoupling capacitor placed adjacent to pin |
Key Features
| Feature | Design Value |
|---|---|
| Dual synchronized Smart Reset™ inputs | SR0 and SR1 must both be asserted low for full tSRC delay - prevents false resets from single-point ESD or noise glitches |
| Factory-programmed tREC = 360 ms | Guarantees consistent reset pulse width independent of user button release timing - eliminates MCU boot failure due to premature RST deassertion |
| Test mode with feedback | Overvoltage on SR0 triggers visible RST assertion (or sustained low) and enables 21 ms tSRC-SHORT - allows in-system functional verification without full power cycle |
| Ultra-low ICC = 1.5 µA (typ.) | Minimizes quiescent drain on primary battery - critical for multi-month operation in activity trackers and smartwatches |
| Undervoltage lockout (UVLO) | RST deasserts cleanly below 1.575 V (typ.) and remains valid down to 1.0 V - prevents erratic MCU behavior during brown-out conditions |
Applications
| Activity Tracker Recovery | Smartwatch System Initialization |
|---|---|
|
Use Scenario: User holds both side buttons for >10 s after firmware freeze to force full system reboot. IC Role / Device Role / Timing Role: Dual-input Smart Reset™ supervisor enforcing 10 s setup delay and delivering 360 ms guaranteed reset pulse to application MCU. Use Value: Eliminates need for dedicated reset button; prevents accidental resets during daily wear while enabling reliable field recovery. |
Use Scenario: During cold start, dual-button press initiates bootloader reinitialization after failed OTA update. IC Role / Device Role / Timing Role: Supervisor coordinating synchronized input detection and precise 360 ms reset assertion to meet ARM Cortex-M reset timing requirements. Use Value: Ensures minimum reset pulse width compliance for secure boot sequence - avoids partial flash corruption or boot loop. |
| Smartglasses Firmware Reset | Wearable Health Monitor Recovery |
|
Use Scenario: User performs long-press on temple controls to recover from sensor driver hang without removing device. IC Role / Device Role / Timing Role: Low-power reset controller interfacing directly with capacitive touch inputs and asserting open-drain RST to SoC. Use Value: Enables seamless, non-invasive recovery in head-worn form factor - no physical reset hole required. |
Use Scenario: ECG module fails to respond; user presses two designated housing buttons for >10 s to trigger diagnostic reset. IC Role / Device Role / Timing Role: Safety-aware supervisor with UVLO protection that deasserts RST below 1.575 V to prevent unstable MCU operation during battery sag. Use Value: Maintains functional safety boundary by ensuring reset integrity across full battery discharge curve (1.8 V → 1.0 V). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Smart Reset™ supervisor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX6369KA+T | Single-input, 1.25 s fixed tSRC; no tREC; higher ICC = 5 µA | Lacks dual-input synchronization and programmable tREC - unsuitable for coordinated wearable recovery workflows | Select only if single-button interface and lower cost outweigh need for extended delay and guaranteed pulse width |
| TPS3808G33DBVR | Power-on reset only; no push-button Smart Reset™ logic; fixed 200 ms reset pulse | No tSRC delay or dual-input capability - cannot replace SR2UABU's intentional long-press recovery function | Use only for basic POR supervision in non-wearable, non-user-initiated reset contexts |
Compared with MAX6369KA+T and TPS3808G33DBVR, SR2UABU uniquely delivers factory-configured 10 s dual-input delay and 360 ms fixed reset pulse - essential for wearable user-recovery UX and MCU timing compliance, whereas alternatives lack either the extended delay logic or deterministic pulse control.
Availability
SR2UABU is available at Aetrix Electronics and suitable for activity tracker recovery, smartwatch system initialization, and smartglasses firmware reset requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for SR2UABU includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power management ICs, sensors, and analog products for industrial, automotive, and consumer markets.
SR2UABU belongs to ST's Smart Reset™ supervisor product line, engineered specifically for ultra-low-power wearable electronics where reliable, user-initiated system recovery must coexist with aggressive energy constraints and minimal PCB area.
FAQ
What is the exact factory-programmed tSRC and tREC for SR2UABU?
SR2UABU is factory-programmed with tSRC = 10.0 s (typ., ±20% over temperature) and tREC = 360 ms (typ., ±33%). These values are laser-trimmed during production and cannot be modified in-circuit. The tSRC delay is implemented using an internal RC oscillator calibrated at 25 °C, and tREC is a fixed digital timer value.
Can SR2UABU be used with a single push-button instead of two?
Yes - the datasheet explicitly permits tying SR0 and SR1 together to implement single-button operation. In this configuration, the same mechanical switch drives both inputs, preserving the full 10 s tSRC delay and 360 ms tREC behavior. No external logic or additional components are required.
Does SR2UABU provide power-on reset (POR) functionality?
No - SR2UABU has no power-on reset circuitry. It only responds to asserted SR0/SR1 inputs after VCC stabilizes within 1.65–5.5 V. If POR is required, a separate POR IC (e.g., STM6601) must be used in parallel, or the host MCU's internal POR must be relied upon.
Is the internal pull-up resistor on RST enabled by default in SR2UABU?
Yes - per Table 7 in the datasheet, SR2UABU's marking "UC" confirms it includes the internal output pull-up resistor on RST. This eliminates the need for an external pull-up when interfacing with standard CMOS inputs, reducing BOM count and PCB area in space-constrained designs.
SR2UABU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- Smart Reset™
- Package/Case:
- 6-UDFN
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Reset Timer
- Number of Voltages Monitored:
- 1
- Voltage - Threshold:
- Adjustable/Selectable
- Output:
- Open Drain or Open Collector
- Reset:
- Active Low
- Reset Timeout:
- 240ms Minimum
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 6-UDFN (1.45x1)
SR2UABU FAQ
1.How can I place an order for SR2UABU through Aetrix?
Please submit a Request for Quotation (RFQ) for SR2UABU on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for SR2UABU reliable?
The price and inventory of SR2UABU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SR2UABU is usually 5 days.
3.What payment methods are accepted for SR2UABU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SR2UABU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SR2UABU?
SR2UABU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SR2UABU order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for SR2UABU?
For technical support, including SR2UABU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SR2UABU requirements.
6.How does Aetrix verify that SR2UABU is sourced from the original manufacturer or authorized distributors?
All SR2UABU products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SR2UABU meets industry standards.
7.What is the process for return or replacement of SR2UABU?
All SR2UABU units undergo pre-shipment inspection (PSI). If there is an issue with SR2UABU, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The SR2UABU part is unused and in its original packaging.
Return procedure for SR2UABU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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