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STMicroelectronics SR2UARU
- Part No.:
- SR2UARU
- Manufacturer:
- STMicroelectronics
- Category:
- Supervisors
- Package:
- 6-UDFN
- Datasheet:
-
SR2UARU.pdf
- Description:
- IC SUPERVISOR 1 CHANNEL 6UDFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,045
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Product details
Overview
SR2UARU from STMicroelectronics is a 6-pin Smart Reset™ supervisor IC designed for ultra-low-power wearable systems, featuring dual active-low push-button inputs (SR0/SR1), factory-programmed 10 s Smart Reset™ setup delay (tSRC), open-drain active-low reset output (RST), and operation across 1.65 V to 5.5 V supply range with only 1.5 µA typical supply current.
For engineers reviewing the SR2UARU datasheet, SR2UARU pinout, SR2UARU application, or SR2UARU equivalent, this device addresses critical requirements in space-constrained, battery-powered wearables where inadvertent short-press resets must be rejected while enabling reliable hard reset via extended button hold - all without power-on reset functionality.
Technical Context
The SR2UARU implements dual-input Smart Reset™ logic requiring simultaneous assertion of both SR0 and SR1 for ≥10 s (typ.) before asserting RST; it lacks power-on reset and relies on external microcontroller coordination for system initialization. Its test mode is triggered by overvoltage on SR0 (VCC + 0.9–1.4 V), initiating a shortened 42 ms tSRC-INI timer.
Reset pulse behavior is push-button controlled (no fixed tREC): RST deasserts immediately upon release of either SR input, making timing fully user-determined. Input logic thresholds are fixed (VIL ≤ 0.3 V, VIH ≥ 0.85 VCC), and undervoltage detection deasserts RST below 1.575 V (typ.), maintaining valid output states down to 1.0 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply voltage | 1.65 V to 5.5 V - supports single-cell Li-ion, coin cell, and multi-rail embedded systems without level-shifting. |
| Supply current | 1.5 µA (typ. at VCC = 5.0 V) - enables multi-year battery life in always-on wearable applications. |
| tSRC delay | 10.0 s (factory-programmed, ±20% over -40°C to +85°C) - rejects accidental presses while enabling deliberate system recovery. |
| Reset output type | Open-drain, active-low RST with optional internal pull-up - compatible with mixed-voltage MCUs and flexible external pull-up selection. |
| Input configuration | Dual active-low Smart Reset™ inputs (SR0, SR1) with fixed logic thresholds - eliminates need for external debouncing or RC networks. |
| 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 PCB area savings in compact form factors like smartwatches. |
Pinout & Package
SR2UARU is housed in a 6-pin UDFN package (1.6 mm × 1.3 mm, 0.4 mm pitch), RoHS-compliant and halogen-free per ECOPACK®2 standards. Pin 1 is marked by a dot; Pin 4 is NC (not bonded) and must be connected to VSS.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 VSS | Supply ground | Reference return path for all internal circuitry; requires low-impedance connection to system ground plane. |
| 2 SR1 | Secondary Smart Reset™ input | Active-low push-button input; internally compatible with optional pull-up; must be held low simultaneously with SR0 for tSRC. |
| 3 RST | Reset output | Open-drain, active-low output; requires external pull-up unless internal option selected; asserts only after both SR inputs meet tSRC condition. |
| 4 NC | No connect | Not bonded die pad; electrically isolated and must be tied to VSS for 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 shortened tSRC-INI when overvolted. |
| 6 VCC | Supply voltage | 1.65–5.5 V input; requires 0.1 µF ceramic decoupling capacitor placed adjacent to pin for noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| Dual Smart Reset™ inputs | Simultaneous SR0+SR1 assertion required for reset - prevents spurious resets from single-point failures or ESD glitches. |
| Factory-programmed tSRC | 10.0 s delay (±20% over full temp range) - eliminates external timing components and ensures consistent user experience across production units. |
| Test mode with feedback | Voltage-triggered entry (SR0 > VCC + 0.9 V) and visible RST assertion - enables in-system validation without dedicated test equipment. |
| Ultra-low ICC | 1.5 µA typical at 5 V - reduces quiescent load on primary battery, critical for multi-month wearable deployments. |
| Undervoltage-safe RST | RST deasserts cleanly below 1.575 V and remains valid down to 1.0 V - avoids metastable reset states during brownout conditions. |
Applications
| Activity Tracker | Smartwatch |
|---|---|
|
Use Scenario: User holds side button for >10 s to force reboot after firmware hang or sensor lockup. IC Role / Device Role / Timing Role: Dual-input Smart Reset™ supervisor coordinating with MCU interrupt pins to distinguish short-press (interrupt) vs. long-press (hard reset). Use Value: Eliminates need for dedicated reset button; leverages existing UI controls while preventing accidental reboots during daily handling. |
Use Scenario: System recovery initiated via crown or side button combination during display freeze or Bluetooth disconnection. IC Role / Device Role / Timing Role: Provides deterministic 10 s reset window with glitch-immune dual-input logic, ensuring reset only occurs after intentional user action. Use Value: Enables reliable field recovery without exposing users to exposed test points or service-mode sequences. |
| Smartglasses | Wearable Health Monitor |
|
Use Scenario: Reboot triggered by simultaneous press of temple and frame buttons during AR overlay crash or IMU calibration failure. IC Role / Device Role / Timing Role: Acts as hardware-enforced reset arbiter - both SR inputs must remain asserted for full tSRC before RST activates. Use Value: Prevents false resets from mechanical vibration or electrostatic discharge on exposed touch surfaces. |
Use Scenario: Forced restart after ECG signal dropout or battery reporting anomaly persists beyond software watchdog timeout. IC Role / Device Role / Timing Role: Delivers clean, open-drain active-low reset pulse synchronized to user intent - no minimum pulse width guarantee required. Use Value: Supports fail-safe recovery in medical-grade wearables without adding complexity to MCU firmware reset handling. |
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 push-button input; fixed 1.25 s reset delay; no test mode; higher ICC (5 µA) | Lacks dual-input safety logic and programmable tSRC - suitable only for simpler, non-wearable reset needs | Select only if board space allows SO-8 and dual-input rejection is unnecessary |
| TPS3808G18DBVR | Power-on reset only; no push-button interface; 1.8 V fixed threshold; no tSRC logic | Provides POR only - cannot replace SR2UARU's user-initiated extended-reset functionality | Use only for basic supply monitoring where manual reset is handled entirely in firmware |
Compared with MAX6369KA+T and TPS3808G18DBVR, SR2UARU uniquely delivers dual-input, user-controllable extended reset timing in a 1.6 mm × 1.3 mm footprint - essential for modern wearables requiring both safety and intuitive recovery.
Availability
SR2UARU is available at Aetrix Electronics and suitable for activity trackers, smartwatches, and smartglasses requiring stable component supply, long-term lifecycle support, and ultra-small footprint reset supervision.
Supply support for SR2UARU 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, analog ICs, MEMS, and power management solutions for industrial, automotive, and consumer markets.
SR2UARU belongs to ST's Smart Reset™ supervisor product line, engineered specifically for battery-powered portable electronics where robust, user-intuitive hardware reset control is mandatory without increasing bill-of-materials or PCB area.
FAQ
Does SR2UARU provide power-on reset (POR) functionality?
No. SR2UARU does not include power-on reset circuitry. It relies entirely on user-initiated dual-button press for reset assertion. System initialization must be handled separately by the host MCU or an external POR IC. The device only monitors SR0/SR1 states and asserts RST after the programmed tSRC delay.
Can SR2UARU's tSRC delay be changed after manufacturing?
No. SR2UARU's tSRC is factory-programmed to 10.0 s (typ.) and is not field-adjustable. This value is laser-trimmed during production and cannot be modified via software, external components, or configuration pins. For variable delays, consider SR2HARU (4.0 s) or SR2PARU (7.5 s) variants.
What happens to RST output when VCC drops below 1.575 V?
When VCC falls below 1.575 V (typ.), SR2UARU deasserts RST and holds it inactive. Output logic levels remain valid down to VCC = 1.0 V, ensuring predictable behavior during brownout conditions without floating or metastable states - critical for safe shutdown sequencing in wearables.
Is Pin 4 (NC) required to be connected externally?
Yes. Although Pin 4 is labeled "NC" and not bonded internally, STMicroelectronics specifies it must be connected to VSS (ground) on the PCB. This connection improves thermal dissipation, mechanical stability of the UDFN package, and reduces susceptibility to solder voiding during reflow - omission may impact long-term reliability.
SR2UARU 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:
- Adjustable/Selectable
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 6-UDFN (1.45x1)
SR2UARU FAQ
1.How can I place an order for SR2UARU through Aetrix?
Please submit a Request for Quotation (RFQ) for SR2UARU 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 SR2UARU reliable?
The price and inventory of SR2UARU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SR2UARU is usually 5 days.
3.What payment methods are accepted for SR2UARU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SR2UARU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SR2UARU?
SR2UARU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SR2UARU 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 SR2UARU?
For technical support, including SR2UARU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SR2UARU requirements.
6.How does Aetrix verify that SR2UARU is sourced from the original manufacturer or authorized distributors?
All SR2UARU 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 SR2UARU meets industry standards.
7.What is the process for return or replacement of SR2UARU?
All SR2UARU units undergo pre-shipment inspection (PSI). If there is an issue with SR2UARU, 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 SR2UARU part is unused and in its original packaging.
Return procedure for SR2UARU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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