STMicroelectronics SR1HARU

Overview

SR1HARU from STMicroelectronics is a 4-pin Smart Reset™ supervisor IC with factory-programmed 4.0 s Smart Reset delay (tSRC), active-low open-drain reset output (RST), and no fixed tREC - enabling push-button-controlled reset pulse width. It operates from 2.0 V to 5.5 V, draws only 1 µA supply current, and features integrated test mode with overvoltage-triggered entry. Used in wearable electronics for reliable user-initiated hard resets without accidental triggering.

For engineers reviewing the SR1HARU datasheet, SR1HARU pinout, SR1HARU application, or SR1HARU equivalent, this device delivers precise extended-reset timing control, voltage-domain flexibility via fixed SR logic thresholds, low-power supervision for battery-constrained wearables, and robust glitch immunity in compact UDFN6 packaging.

Technical Context

The SR1HARU implements a deterministic digital counter-based Smart Reset delay (tSRC = 4.0 s typ.) triggered by sustained low assertion on the SR input. Its logic diagram confirms independent SR input sampling and RST output assertion timing, with no internal clock source required beyond VCC.

Test mode activation occurs only when SR exceeds VCC + 1.1 V (typ.), initiating a shortened 42 ms initial delay (tSRC-INI) and locking RST low until VCC power cycle. The device guarantees high-impedance RST during undervoltage conditions and supports dual-voltage-domain operation via fixed VIH/VIL thresholds.

Key Specifications

Pinout & Package

SR1HARU is housed in a 6-pin UDFN package (1.00 mm × 1.45 mm × 0.50 mm height, 0.50 mm pitch). Pins 5 and 6 are not bonded and must be connected to VSS for mechanical stability and thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6326UR29+T and TPS3808G12DBVR, SR1HARU uniquely integrates factory-programmed tSRC delay, push-button-native logic, and voltage-domain isolation - making it optimal for wearable UI recovery where button multiplexing and ultra-low ICC are critical.

Availability

SR1HARU is available at Aetrix Electronics and suitable for activity trackers, smartwatches, and smartglasses requiring stable component supply, long-term manufacturability, and RoHS-compliant UDFN packaging.

Supply support for SR1HARU 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 devices for industrial, automotive, and consumer markets.

SR1HARU belongs to ST's Smart Reset™ supervisor product line, engineered specifically for intuitive, low-power, push-button-initiated system recovery in compact portable electronics - prioritizing user experience and board-space efficiency over traditional voltage-monitoring functions.

FAQ

What is the exact Smart Reset delay (tSRC) programmed into SR1HARU?

The SR1HARU has a factory-programmed Smart Reset delay of 4.0 seconds (typical), with ±20% variation over the full operating temperature range (-40 °C to +85 °C). This value is laser-trimmed during production and cannot be modified in-circuit or via software.

Does SR1HARU include an internal pull-up resistor on the SR input?

No - the "A" in SR1HARU'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 proper logic high state when the push-button is open.

Can SR1HARU be used with a 1.8 V microcontroller I/O domain?

Yes - the SR input uses fixed logic thresholds (VIL ≤ 0.3 V, VIH ≥ 0.85 × VCC), so when VCC = 2.0–5.5 V, the SR pin accepts 1.8 V logic signals directly without level shifting, provided V(SR) never exceeds VCC + 1.1 V to avoid test mode entry.

Is the RST output truly open-drain, and what pull-up value is recommended?

Yes - SR1HARU's RST is open-drain with no internal pull-up (per "R" in part number). A 10 kΩ external pull-up to the target reset rail (e.g., MCU VDD) is recommended to ensure fast rise time and noise immunity, especially in noisy wearable environments.