STMicroelectronics SR2LABU

Overview

SR2LABU from STMicroelectronics is a 6-pin Smart Reset™ supervisor IC designed for ultra-low-power wearable systems. It features dual active-low push-button inputs (SR0, SR1), factory-programmed 360 ms reset pulse duration (tREC), open-drain active-low reset output (RST), 1.65–5.5 V operating voltage, and 1.5 µA supply current - enabling reliable hard-reset initiation in activity trackers and smartwatches without dedicated reset hardware.

For engineers reviewing the SR2LABU datasheet, SR2LABU pinout, SR2LABU application, or SR2LABU equivalent, this device addresses critical design needs in space-constrained, battery-powered systems requiring glitch-immune, user-initiated system recovery with precise timing control and extended voltage range operation.

Technical Context

The SR2LABU implements a dual-input Smart Reset™ architecture where both SR0 and SR1 must be asserted simultaneously for a factory-configured tSRC delay (6.0 s) before asserting RST. Its reset output is open-drain, active-low, and guaranteed to remain asserted for exactly 360 ms (tREC) regardless of input release timing - eliminating software dependency for reset hold time.

It includes integrated test mode triggered by overvoltage on SR0 (VCC + 0.9 to VCC + 1.4 V), enabling in-system verification with shortened 21 ms tSRC-SHORT delay. Input logic thresholds are fixed (VIL ≤ 0.3 V, VIH ≥ 0.85 VCC), and undervoltage lockout deasserts RST below 1.575 V while maintaining valid output states down to 1.0 V.

Key Specifications

Pinout & Package

SR2LABU is housed in a 1.6 mm × 1.3 mm × 0.55 mm UDFN6 package with 0.40 mm pitch, ECOPACK®2-compliant (RoHS, halogen-free), and optimized for high-density PCB layouts in compact wearables.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SR2LABU (6.0 s tSRC), SR2HABU offers quicker recovery at reduced glitch margin, while SR2UABU increases safety margin at the cost of user latency - all three share identical tREC, package, and power characteristics for drop-in layout compatibility.

Availability

SR2LABU is available at Aetrix Electronics and suitable for activity trackers, smartwatches, and smartglasses requiring stable component supply, long-term manufacturability, and RoHS-compliant packaging.

Supply support for SR2LABU 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, delivering intelligent power, sensing, and control solutions for automotive, industrial, and consumer markets.

The SR2 family is part of ST's Smart Reset™ supervisor product line, engineered specifically for ultra-low-power, space-constrained portable electronics where robust, user-initiated system recovery must coexist with minimal bill-of-materials and zero firmware overhead.

FAQ

What is the function of the NC pin (Pin 4) on SR2LABU?

Pin 4 is a no-connect terminal with no internal bond wire. Per STMicroelectronics' datasheet (DocID026047 Rev 2, Section 2), it must be externally connected to VSS to ensure mechanical stability during reflow, improve thermal dissipation, and reduce EMI susceptibility - leaving it floating violates recommended PCB layout practice.

Can SR2LABU generate a reset pulse without holding both buttons for the full tSRC duration?

No. The SR2LABU requires both SR0 and SR1 to be held low simultaneously for the entire factory-programmed tSRC delay (6.0 s) before asserting RST. There is no partial or early-trigger mechanism - this concurrent assertion requirement is fundamental to its Smart Reset™ architecture and ensures immunity to single-point glitches or unintended button contact.

Is the 360 ms tREC pulse width adjustable after manufacturing?

No. The tREC value of 360 ms is factory-programmed during wafer sort and cannot be modified in the field or via configuration pins. It is permanently encoded in the device's non-volatile logic and remains fixed across all operating conditions - users selecting SR2LABU commit to this exact pulse duration for system reset timing.

Does SR2LABU include power-on reset (POR) functionality?

No. The SR2LABU explicitly lacks power-on reset - it does not assert RST during VCC ramp-up. System initialization must be handled by the host MCU's internal POR or a separate POR IC. This design choice avoids redundant reset assertion and allows designers to decouple boot sequencing from user-initiated recovery logic.