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Allegro MicroSystems A5303SLETR-T
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- Part No.:
- A5303SLETR-T
- Manufacturer:
- Allegro MicroSystems
- Category:
- Sensor and Detector Interfaces
- Package:
- 20-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
A5303SLETR-T.pdf
- Description:
- IC SMOKE DETECTOR PHOTO 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,054
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Product details
Overview
A5303SLETR-T from Allegro MicroSystems is a discontinued BiCMOS photoelectric smoke detector IC with ultra-low standby current (2.3 μA typ.), 2.3–5.5 V operation, and integrated interconnect, timer (hush), latching alarm indicator, and triple-horn chirp for UL217/NFPA72 compliance. It drives IR emitters, photodiodes, LEDs, and external sound ICs in battery-powered residential/commercial smoke alarms.
For engineers reviewing the A5303SLETR-T datasheet, A5303SLETR-T pinout, A5303SLETR-T application, or A5303SLETR-T equivalent, key selection considerations include its 20-pin TSSOP package, 10-year battery life capability, I/O networking for multi-unit alarm propagation, programmable gain photoamplifier (via C1/C2), and temporal horn pattern generation for audible alerts.
Technical Context
The A5303SLETR-T integrates a variable-gain photoamplifier with dual external capacitor control (C1 for supervisory/high-gain mode, C2 for standby/low-gain mode), internal oscillator with 10.5 ms typical period, and three-stage speedup sensing to reduce time-to-alarm while suppressing false triggers. Gain shifts automatically: low gain during standby/timer, +45% hysteresis gain during local alarm, and high gain during pushbutton test or chamber monitoring.
Its timing architecture uses STROBE (VDD – 2 V regulated output) as low-side reference for photoamplifier circuitry, OSC CAP and TRES pins to configure oscillator timing (10.5 ms low time, 105 μs high time), and I/O pin with internal NMOS charge dump for noise-immune interconnection across distributed detectors. Logic outputs SOUT0/SOUT1/SOUT2 encode six distinct states (standby, local/remote alarm, test pass/fail, low-battery, degraded chamber) in 3-bit CMOS push-pull format.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 2.3–5.5 V - supports single 3 V coin cell or alkaline battery without regulation |
| Standby Current | 2.3 μA typ. - enables >10-year operation on standard CR123A or AA batteries |
| Photoamp Gain Control | Externally set via C1 (supervisory) and C2 (standby); C2 = 4700 pF typical for low-gain mode |
| Oscillator Period | 10.5 ms typ. - defines STROBE pulse width and base timing for smoke sampling intervals |
| IRED Drive Current | 100 mA typ. (RISET = 3 Ω) - sufficient for IR LED illumination in optical chamber with 300 mA max setting |
| Interconnect Latency | 96.8 ms max - two consecutive I/O samples + one additional clock required before remote alarm activation |
| Horn Output Timing | 500 ms on-time, 500 ms off-time, 1500 ms final off-time - implements UL217-compliant temporal pattern |
Pinout & Package
Package: 20-pin TSSOP (JEDEC MO-153AC), thin profile (<1.2 mm height), Pb-free with 100% matte tin leadframe plating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SOUT1, SOUT0, SOUT2 | 3-bit logic outputs | Encode device state (standby, local/remote alarm, test pass/fail, low-battery, degraded chamber) for external sound IC control |
| I/O | Input-output bus | Enables daisy-chained interconnection of multiple units; drives high on local alarm to trigger all connected alarms |
| STROBE | Regulated reference output | Provides VDD – 2 V stable low-side reference for photoamplifier circuitry; strobed to minimize power |
| DETECT | Photoamplifier input | Connects to photodiode cathode; zero-bias operation requires low-dark-current, low-capacitance photodiode |
| C1, C2 | Gain-setting capacitors | C1 sets high gain for test/chamber monitor; C2 sets low gain for standby; gain = 1 + (C / 12 pF) |
| ISET | IRED current programming | Resistor to VSS sets IRED drive current per IIRED (mA) ≈ 300 / RISET (Ω) |
| HUSH | Timer mode enable/reference | High >50 mV enables 10-min hush mode; also forms resistive divider with R1/R2 to lower comparator threshold during timer |
| TEST | Manual test/timer trigger | Pull-high initiates push-to-test; high-to-low transition resets latching alarm and starts timer if enabled |
| LED | Open-drain NMOS output | Directly drives visible LED; blinks every 0.5 s during local alarm, every 43 s in standby (if BLINK = VDD) |
| HORN | Horn driver enable | Logic-high output enables external boost converter for piezo horn; not used if horn omitted |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low standby current | 2.3 μA typ. enables >10-year battery life on standard 3 V primary cells without voltage regulation |
| Programmable photoamplifier gain | Two external capacitors (C1/C2) allow independent optimization of sensitivity for standby vs. test/chamber monitoring modes |
| Interconnect with noise immunity | I/O pin samples every 43 ms; requires two consecutive high samples plus one additional clock to activate remote alarm, rejecting sub-9-cycle noise pulses |
| Latching alarm indicator | Initiating detector(s) pulse LED every 43 s for 24 hours after alarm clears, enabling physical identification in multi-unit installations |
| UL217/NFPA72 temporal horn pattern | Built-in timing generates 0.5 s on / 0.5 s off / 0.5 s on / 0.5 s off / 0.5 s on / 1.5 s off sequence for compliant audible alerts |
Applications
| Residential Smoke Alarms | Commercial Ceiling-Mounted Detectors |
|---|---|
Use Scenario: Battery-powered ceiling-mounted smoke alarm in apartment units with interconnected wiring. IC Role / Device Role / Timing Role: A5303SLETR-T serves as the core signal processing and alarm coordination IC, detecting scattered IR light from smoke particles and propagating alarms via I/O bus. Use Value: Enables synchronized alarm activation across units using only two-wire interconnect, eliminating need for separate notification appliances while meeting UL217 interconnection requirements. | Use Scenario: Hardwired commercial smoke detector with battery backup and self-diagnostic capability. IC Role / Device Role / Timing Role: A5303SLETR-T provides chamber sensitivity monitoring, low-battery detection, and hush functionality while driving both visible LED and external piezo horn via HORN/SOUTx outputs. Use Value: Reduces maintenance burden through automatic degraded-chamber warnings (two failed tests) and low-battery alerts with 43-second chirp interval, extending service intervals in large-scale deployments. |
| Hotel Room Safety Systems | Multi-Family Housing Intercom Alarms |
Use Scenario: Hotel room smoke detector linked to central fire panel and guest room doorbell system. IC Role / Device Role / Timing Role: A5303SLETR-T acts as local alarm initiator and status reporter; its latching alarm indicator identifies the first-activated unit when multiple rooms alarm simultaneously. Use Value: Allows staff to locate origin of fire event within seconds by observing which unit's LED pulses post-alarm, improving emergency response accuracy in distributed lodging environments. | Use Scenario: Condominium hallway smoke detector networked to individual unit door chimes for localized alerting. IC Role / Device Role / Timing Role: A5303SLETR-T coordinates alarm propagation over shared I/O line while suppressing LED activity during remote alarms to avoid confusing occupants in non-affected units. Use Value: Provides targeted occupant notification without full building evacuation, leveraging built-in remote alarm suppression logic that disables LED blinking when alarm originates externally. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar photoelectric smoke detector IC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ISL28022IRZ-T7A | Low-power op-amp with rail-to-rail I/O and 1.5 μA quiescent current; no integrated smoke logic, timer, or I/O networking | Requires external MCU, oscillator, and discrete logic to replicate A5303SLETR-T functionality; suitable only for custom-designed detector platforms | Select only when full architectural flexibility is needed and BOM cost is secondary to design control |
| MAX44267ASA+ | Ultra-low-noise, low-drift amplifier with 1.2 μA supply current; lacks photoamplifier gain switching, STROBE reference, or UL-compliant horn timing | Cannot implement temporal horn pattern or interconnect logic without external timing ICs and microcontroller firmware | Choose for analog front-end enhancement in hybrid designs where A5303SLETR-T handles digital logic and MAX44267 handles precision amplification |
Compared with ISL28022IRZ-T7A and MAX44267ASA+, the A5303SLETR-T delivers fully integrated smoke detection logic-including programmable gain photoamplifier, UL217 horn timing, I/O networking, and latching alarm-reducing system-level component count by ≥7 ICs and eliminating firmware development for core alarm functions.
Availability
A5303SLETR-T is available at Aetrix Electronics and suitable for residential fire safety systems, commercial ceiling-mounted detectors, and hotel room safety systems requiring stable component supply despite end-of-life status.
Supply support for A5303SLETR-T 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
Allegro MicroSystems is a U.S.-based semiconductor company specializing in high-performance magnetic sensing, power ICs, and sensor interface solutions for automotive, industrial, and consumer markets.
The A5303 product line was designed specifically for battery-operated photoelectric smoke detectors, integrating analog signal conditioning, digital alarm logic, interconnect capability, and UL217-compliant timing into a single 20-pin TSSOP package to simplify certified fire-safety product development.
FAQ
What is the operating voltage range for the A5303SLETR-T?
The A5303SLETR-T operates from 2.3 V to 5.5 V, making it compatible with common 3 V lithium coin cells or alkaline batteries without requiring external voltage regulation. This wide range ensures reliable function across battery discharge curves and accommodates variations in cell chemistry and aging, directly supporting the 10-year battery life claim under typical standby conditions.
How does the A5303SLETR-T implement interconnect functionality between multiple smoke detectors?
The A5303SLETR-T uses its I/O pin as a bidirectional bus: during standby, it samples the line every ~43 ms; upon detecting two consecutive high samples plus one additional clock cycle, it activates local alarm outputs and drives I/O high to propagate the alarm. An internal NMOS charge dump aids noise immunity in distributed installations. This eliminates need for external transceivers or microcontrollers to coordinate multi-unit alarms.
What is the purpose of the C1 and C2 pins on the A5303SLETR-T?
The C1 and C2 pins on the A5303SLETR-T set photoamplifier gain for different operational modes: C1 configures high gain during pushbutton test and chamber monitoring (Ae = 1 + C1/12 pF), while C2 sets low gain during standby (Ae = 1 + C2/12 pF). C2 also enables +45% hysteresis gain increase during local alarm. Typical values are 47 nF for C1 and 4700 pF for C2, allowing precise sensitivity tuning per optical chamber design.
Does the A5303SLETR-T support UL217 and NFPA72 compliance out of the box?
Yes, the A5303SLETR-T implements the UL217/NFPA72 Temporal Horn Pattern (0.5 s on / 0.5 s off / 0.5 s on / 0.5 s off / 0.5 s on / 1.5 s off) via its HORN output timing and supports interconnect, latching alarm indicator, and low-battery warning-all required elements for certification. Its integrated timing eliminates need for external oscillators or firmware to meet these standards.
Is the A5303SLETR-T still recommended for new designs?
No, the A5303SLETR-T is a discontinued product; Allegro MicroSystems states it should not be purchased for new design applications. Samples are no longer available, and production has ceased. For existing designs, Aetrix Electronics provides last-time-buy support and lifecycle coordination, but new projects should evaluate alternative solutions with active production status and long-term supply assurance.
A5303SLETR-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Allegro MicroSystems
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width)
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Smoke Detector
- Input Type:
- Photoelectric
- Output Type:
- Voltage
- Current - Supply:
- 300 µA
- Operating Temperature:
- -20°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP
A5303SLETR-T FAQ
1.How can I place an order for A5303SLETR-T through Aetrix?
Please submit a Request for Quotation (RFQ) for A5303SLETR-T 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 A5303SLETR-T reliable?
The price and inventory of A5303SLETR-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for A5303SLETR-T is usually 5 days.
3.What payment methods are accepted for A5303SLETR-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for A5303SLETR-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for A5303SLETR-T?
A5303SLETR-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your A5303SLETR-T 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 A5303SLETR-T?
For technical support, including A5303SLETR-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your A5303SLETR-T requirements.
6.How does Aetrix verify that A5303SLETR-T is sourced from the original manufacturer or authorized distributors?
All A5303SLETR-T 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 A5303SLETR-T meets industry standards.
7.What is the process for return or replacement of A5303SLETR-T?
All A5303SLETR-T units undergo pre-shipment inspection (PSI). If there is an issue with A5303SLETR-T, 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 A5303SLETR-T part is unused and in its original packaging.
Return procedure for A5303SLETR-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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