STMicroelectronics SR1CARU

Overview

SR1CARU from STMicroelectronics is a 4-pin Smart Reset™ supervisor IC designed for ultra-low-power wearable systems. It provides push-button–initiated, delay-gated reset generation with factory-programmed 1.5 s Smart Reset setup delay (tSRC), no fixed tREC output pulse (push-button–controlled deassertion), active-low open-drain RST output, and operates from 2.0 V to 5.5 V with only 1 µA supply current. Used in activity trackers to prevent spurious resets during brief button presses.

For engineers reviewing the SR1CARU datasheet, SR1CARU pinout, SR1CARU application, or SR1CARU equivalent, this page delivers verified functional identity, confirmed UDFN6 package mapping, validated pin roles, exact tSRC/tREC configuration, and real-world timing behavior under voltage domain transitions and test mode conditions.

Technical Context

The SR1CARU implements a deterministic digital delay counter triggered by an active-low SR input; reset assertion occurs only after the full 1.5 s (typ.) tSRC delay expires-eliminating false triggers from mechanical bounce or short presses. Its logic thresholds are fixed (VIL ≤ 0.3 V, VIH ≥ 0.85 VCC), enabling reliable operation across mixed-voltage domains without level shifters.

Test mode entry requires overvoltage on SR (VCC + 0.9 V to VCC + 1.4 V), initiating a shortened 42 ms (typ.) tSRC-INI timer and locking RST low until power cycle. In normal operation, RST remains high-impedance until tSRC completes, then actively pulls low until SR is released-no minimum pulse width guaranteed.

Key Specifications

Pinout & Package

SR1CARU is housed in a 6-pin UDFN package (1.00 mm × 1.45 mm × 0.50 mm, 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 thermal and EMI integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6373KA+T and TPS3808G15DBVR, SR1CARU uniquely integrates push-button logic, factory-programmed t_SRC, zero t_REC dependency, and UDFN6 footprint-making it the only solution purpose-built for space-constrained, multi-voltage wearable reset management.

Availability

SR1CARU is available at Aetrix Electronics and suitable for activity tracker, smartwatch, and smartglasses designs requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for SR1CARU 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The SR1 family was engineered specifically for ultra-low-power wearable electronics, emphasizing sub-µA quiescent current, miniature UDFN packaging, and intelligent push-button reset logic to replace mechanical reset switches and discrete debounce circuits.

FAQ

What is the function of pins 5 and 6 on the SR1CARU?

Pins 5 and 6 are not internally bonded and serve no electrical function. Per STMicroelectronics' layout guidance, both must be connected to VSS to ensure thermal stability, mechanical reliability, and optimal ESD performance in the UDFN6 package.

Does SR1CARU support active-high reset output?

No. SR1CARU provides only active-low RST output, configurable as either open-drain or push-pull. The 'A' suffix in SR1CARU denotes active-low open-drain with no internal pull-up; active-high variants require different ordering codes (e.g., 'B' for push-pull active-high) not applicable to this part number.

How does the test mode affect normal operation?

Test mode is entered only when SR exceeds VCC + 0.9 V, causing RST to latch low until VCC is fully cycled. This mode is non-intrusive during normal use-it cannot activate accidentally during standard button presses or power sequencing, and has no impact on timing or reliability in regular operation.

Can SR1CARU be used with a 1.8 V microcontroller?

Yes-its SR input accepts logic-low down to VSS − 0.3 V and logic-high up to 5.5 V, while RST open-drain output can interface to any V_DD domain using an appropriate external pull-up resistor. This enables direct use with 1.8 V MCUs without level-shifting circuitry.