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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Supervisors

STMicroelectronics SR1LARU

Name: SR1LARU
Brand: STMicroelectronics
SKU: SR1LARU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SR1LARU

Manufacturer:: STMicroelectronics

Category:: Supervisors

Package:: 6-UDFN

Datasheet:: SR1LARU.pdf

Description:: IC SUPERVISOR 1 CHANNEL 6UDFN

Quantity:: RFQ Add To RFQ list

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Inventory:5,232

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Product details

Overview

SR1LARU from STMicroelectronics is a 4-pin Smart Reset™ supervisory IC with factory-programmed 6.0 s Smart Reset input delay (tSRC), active-low open-drain reset output (RST), and no fixed reset pulse width (tREC = push-button controlled). It operates from 2.0 V to 5.5 V, draws only 1 µA supply current, and features integrated test mode for in-system validation. Used in wearable electronics to prevent spurious resets from brief button presses while enabling hard reset after sustained press.

For engineers reviewing the SR1LARU datasheet, SR1LARU pinout, SR1LARU application, or SR1LARU equivalent, this page delivers verified technical context, UDFN6 package mapping, tSRC/tREC configuration details, real-world timing behavior, and alternative selection guidance for low-power portable reset supervision.

Technical Context

The SR1LARU implements a deterministic, temperature-stable Smart Reset delay (tSRC = 6.0 s typ., ±20% over -40 °C to +85 °C) triggered by an active-low SR input. Its logic ensures RST remains asserted only while SR is held low - no minimum or fixed pulse width is guaranteed, making reset duration fully user-controlled via button release timing.

Test mode entry requires SR voltage > VCC + 1.1 V (typ.), initiating a shortened 42 ms initial delay (tSRC-INI) and locking RST low until power cycle. The device supports mixed-voltage domain operation via fixed SR input thresholds and open-drain RST, with guaranteed high-Z behavior during undervoltage conditions.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	2.0 V to 5.5 V - supports single-supply operation across Li-ion, coin-cell, and 3.3 V/5 V systems without level-shifting.
Supply Current (I_CC)	1.0 µA typ. at 25 °C - enables multi-year battery life in wearables with infrequent reset events.
t_SRC Delay	6.0 s typ. (factory-programmed), ±20% over full temp range - prevents accidental reset from short button presses while ensuring reliable recovery on sustained press.
RST Output Type	Active-low, open-drain - allows flexible pull-up selection and voltage-domain isolation between MCU and reset circuitry.
Operating Temp	-40 °C to +85 °C - qualified for consumer wearable environments including skin-contact devices and outdoor activity trackers.
Input Logic Thresholds	V_IL ≤ 0.3 V, V_IH ≥ 0.85 V_CC - provides robust noise immunity and predictable transition across supply voltages.
Package	UDFN6 (1.00 mm × 1.45 mm, 0.5 mm pitch) - ultra-compact footprint ideal for space-constrained smartwatches and earbuds.

Pinout & Package

SR1LARU is housed in a 6-pin UDFN package (1.00 mm × 1.45 mm × 0.50 mm height, 0.50 mm pitch), RoHS-compliant and halogen-free per ECOPACK®2. Pins 5 and 6 are not bonded and must be connected to VSS for mechanical stability and thermal performance.

Pin/Terminal	Circuit Role	Design Meaning
1	RST	Active-low open-drain reset output - requires external pull-up; asserts only while SR is held low; de-asserts immediately upon SR release.
2	VSS	Ground reference - must be low-impedance connection; decoupling capacitor (0.1 µF) placed between VSS and VCC.
3	SR	Smart Reset input, active-low - no internal pull-up (per "A" in part number); requires external pull-up or MCU-driven control.
4	VCC	Positive supply - accepts 2.0–5.5 V; powers internal timing circuitry and logic; must ramp before or with SR voltage to avoid test mode.
5	NC	Not connected (not bonded) - electrically isolated; must be soldered to VSS for PCB mechanical integrity and thermal dissipation.
6	NC	Not connected (not bonded) - electrically isolated; must be soldered to VSS for PCB mechanical integrity and thermal dissipation.

Key Features

Feature	Design Value
Programmable Smart Reset Delay	tSRC = 6.0 s factory-set (0.5 s–10 s range available), eliminating need for external RC timing components and reducing BOM count.
Push-Button Controlled Reset Pulse	No fixed tREC - RST de-asserts instantly when SR is released, enabling precise software-interrupt vs. hardware-reset distinction in firmware.
Integrated Test Mode	Triggered by overvoltage on SR (> VCC + 1.1 V), providing observable RST lock for production line functional testing without external equipment.
Ultra-Low Quiescent Current	1.0 µA typical supply current - extends battery life in always-on wearables where reset supervision runs continuously.
Mixed-Voltage Domain Support	Fixed SR input thresholds and open-drain RST allow use with MCUs operating at different VDD levels (e.g., 1.8 V MCU with 3.3 V VCC).

Applications

Activity Tracker

Smartwatch

Use Scenario: User holds side button for >6 s to force reboot after frozen UI or sensor hang.

IC Role / Device Role / Timing Role: Supervisory IC enforcing extended button-press threshold before asserting active-low reset to application MCU.

Use Value: Prevents accidental reboots from pocket-induced presses while guaranteeing recovery from unresponsive states without requiring disassembly or charging.

Use Scenario: System fails to wake from deep sleep due to corrupted RTC or peripheral state.

IC Role / Device Role / Timing Role: Smart Reset input monitors physical button; 6 s delay ensures only intentional reset triggers RST assertion to main SoC.

Use Value: Enables field-recoverable system reset without relying on software watchdogs that may be disabled during fault conditions.

Smartglasses

Wearable Health Monitor

Use Scenario: Device freezes during AR overlay rendering or IMU fusion lockup.

IC Role / Device Role / Timing Role: Dedicated hardware reset supervisor with open-drain RST isolating reset domain from 1.2 V core logic and 3.3 V display interface.

Use Value: Ensures clean power-cycle of all subsystems regardless of software state, critical for safety-critical visual feedback systems.

Use Scenario: ECG or SpO₂ sensor stops reporting due to firmware crash or memory corruption.

IC Role / Device Role / Timing Role: Low-current (1 µA) reset controller maintaining supervision during multi-week battery operation without measurable drain impact.

Use Value: Guarantees patient-facing device can be recovered in-field using standard button sequence, avoiding clinical downtime or data loss.

Equivalent & Alternatives

The following parts are listed as comparable options for similar Smart Reset supervision applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MAX6326UR29+T	Fixed 2.9 V reset threshold, 140 ms reset pulse, no programmable tSRC; SOT23-3 package.	Designed for voltage-monitoring reset, not push-button supervised reset; lacks Smart Reset logic or extended delay capability.	Select only if primary requirement is brown-out detection-not user-initiated intelligent reset.
TPS3808G12DBVR	Adjustable reset timeout (1.25 ms–10 s via external capacitor), but no dedicated Smart Reset input logic or test mode.	Requires external RC network for timing; no built-in glitch immunity or push-button discrimination logic.	Choose when fine-grained timeout tuning is needed and board space allows capacitor placement; not drop-in for SR1LARU's button-centric function.

Compared with MAX6326UR29+T and TPS3808G12DBVR, SR1LARU uniquely integrates factory-programmed 6 s delay, push-button-controlled RST de-assertion, and test mode-enabling compact, reliable, and production-testable reset supervision in wearables without external timing components or firmware dependency.

Availability

SR1LARU 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 SR1LARU 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.

SR1LARU belongs to ST's Smart Reset™ family - engineered specifically for ultra-low-power, space-constrained portable electronics where reliable, user-initiated hardware reset must coexist with aggressive energy budgets and minimal PCB area.

FAQ

What is the exact Smart Reset delay (tSRC) programmed into SR1LARU?

The SR1LARU has a factory-programmed Smart Reset delay of 6.0 seconds (typical), with tolerance of ±20% over the full operating temperature range (-40 °C to +85 °C). This value is fixed at wafer sort and cannot be modified in-circuit or post-manufacture.

Does SR1LARU include an internal pull-up resistor on the SR input?

No - the "A" in SR1LARU's part number indicates active-low SR input with no internal pull-up resistor. An external pull-up (typically 10–100 kΩ to VCC) is required to ensure defined logic-high state when the push-button is open.

Can SR1LARU drive a reset input directly on a 1.8 V microcontroller?

Yes - the open-drain RST output supports mixed-voltage operation. When used with a 1.8 V pull-up resistor on the RST line, it safely asserts active-low reset to a 1.8 V MCU while powered from a higher VCC (e.g., 3.3 V), provided V(SR) does not exceed VCC + 1.1 V during power-up.

How is test mode triggered and exited on SR1LARU?

Test mode is triggered by applying > VCC + 1.1 V (typ.) to the SR pin - causing RST to lock low until VCC is cycled. Exit requires full power-down: VCC must be brought to 0 V and re-ramped. No software command or timing sequence can exit test mode without power cycling.

SR1LARU 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)

SR1LARU FAQ

1.How can I place an order for SR1LARU through Aetrix?

Please submit a Request for Quotation (RFQ) for SR1LARU 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 SR1LARU reliable?

The price and inventory of SR1LARU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SR1LARU is usually 5 days.

3.What payment methods are accepted for SR1LARU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SR1LARU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SR1LARU?

SR1LARU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SR1LARU 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 SR1LARU?

For technical support, including SR1LARU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SR1LARU requirements.

6.How does Aetrix verify that SR1LARU is sourced from the original manufacturer or authorized distributors?

All SR1LARU 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 SR1LARU meets industry standards.

7.What is the process for return or replacement of SR1LARU?

All SR1LARU units undergo pre-shipment inspection (PSI). If there is an issue with SR1LARU, 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 SR1LARU part is unused and in its original packaging.

Return procedure for SR1LARU:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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