STMicroelectronics SR2HARU

Overview

SR2HARU 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 implements factory-programmed 4.0 s Smart Reset™ setup delay (tSRC) with push-button controlled (no fixed tREC) active-low open-drain reset output (RST), targeting activity trackers and smartwatches.

For engineers reviewing the SR2HARU datasheet, SR2HARU pinout, SR2HARU application, or SR2HARU equivalent, key selection considerations include its dual active-low Smart Reset™ inputs (SR0/SR1), absence of power-on reset, test-mode entry via overvoltage on SR0, UDFN6 package footprint constraints, and compatibility with microcontroller interrupt-driven reset arbitration logic.

Technical Context

The SR2HARU implements a deterministic dual-input reset arbitration architecture: both SR0 and SR1 must be held low simultaneously for ≥4.0 s (tSRC) before asserting RST; release of either input deasserts RST immediately-no minimum pulse width is guaranteed. Its internal timing engine uses temperature-compensated RC oscillation, with tSRC variation ±20% over –40 °C to +85 °C.

Test mode activation occurs when SR0 is pulled to VCC + 0.9–1.4 V, triggering a shortened 42 ms initial timer (tSRC-INI); subsequent SR0/SR1 ground pulses then use 21 ms (tSRC-SHORT) for rapid validation. The device guarantees RST deassertion below 1.575 V and valid output states down to 1.0 V VCC.

Key Specifications

Pinout & Package

SR2HARU is housed in a 6-pin UDFN6 package (1.6 mm × 1.3 mm, 0.4 mm pitch), RoHS-compliant and halogen-free per ECOPACK®2. Pin 1 is marked by a dot; Pin 4 is NC (not bonded) and must be connected to VSS.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6369KA+T and TPS3808G33DBVR, SR2HARU uniquely delivers dual active-low inputs with factory-programmed 4.0 s delay, test-mode diagnostics, and sub-2 µA quiescent current-making it the only fit for space- and power-constrained wearable reset arbitration where user intent must be explicitly validated.

Availability

SR2HARU is available at Aetrix Electronics and suitable for activity trackers, smartwatches, and smartglasses requiring stable component supply, long-term lifecycle support, and RoHS-compliant UDFN packaging.

Supply support for SR2HARU 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.

SR2HARU belongs to ST's Smart Reset™ supervisor product line, engineered specifically for ultra-low-power wearable electronics requiring user-intent-validated hardware reset functionality with minimal board space and energy overhead.

FAQ

Does SR2HARU provide power-on reset (POR) functionality?

No. SR2HARU does not include power-on reset circuitry. It is solely a user-initiated Smart Reset™ supervisor: reset assertion requires deliberate, simultaneous low assertion of both SR0 and SR1 inputs for the full 4.0 s tSRC delay. POR behavior must be implemented externally or by the host MCU.

Can SR2HARU's tSRC delay be changed after manufacturing?

No. The 4.0 s tSRC delay for SR2HARU is factory-programmed and permanently fixed. ST offers other variants (e.g., SR2UARU for 10.0 s) with different tSRC values, but no field-programmable or adjustable timing capability exists within the SR2 family.

What is the purpose of the NC (Pin 4) terminal, and how should it be handled?

Pin 4 is a no-connect terminal-physically unbonded inside the die. It must be soldered to the PCB ground plane (VSS) to ensure mechanical stability, thermal dissipation, and EMI suppression. Leaving it floating may cause solder joint reliability issues or radiated emissions in high-density layouts.

Is an external pull-up resistor required on the RST output?

Yes. SR2HARU's RST output is open-drain and active-low with no internal pull-up resistor (as indicated by "OD, AL" in the marking table). An external pull-up resistor (typically 10–100 kΩ to VCC or host logic rail) is mandatory to establish a defined high state when RST is deasserted.