Texas Instruments LM809M3X-4.63

Overview

LM809M3X-4.63 from Texas Instruments is a 3-pin SOT-23 microprocessor reset supervisor IC with a factory-programmed 4.63 V ±3% precision reset threshold, 240 ms typical active-low reset timeout, and 15 µA typical supply current. It monitors 5 V supply rails in embedded controllers and industrial microprocessor systems to ensure reliable power-up, brown-out, and power-down reset assertion.

For engineers reviewing the LM809M3X-4.63 datasheet, LM809M3X-4.63 pinout, LM809M3X-4.63 application, or LM809M3X-4.63 equivalent, key selection criteria include reset threshold accuracy over temperature (±3% at 25°C, ±6% over –40°C to 105°C), guaranteed RESET validity down to VCC ≥1 V, immunity to VCC transients ≤20 µs at 100 mV underthreshold, and compatibility with bidirectional µP reset pins via 4.7 kΩ series resistor.

Technical Context

The LM809M3X-4.63 implements a precision bandgap-based voltage comparator with internal hysteresis to detect VCC falling below 4.63 V, triggering an active-low RESET output that remains asserted for 240 ms after VCC rises above threshold. Its architecture ensures monotonic reset behavior without chatter during slow-rising VCC transitions.

It operates across –40°C to 105°C with full electrical specification, supports input voltages from 1.0 V to 5.5 V, and maintains functional RESET output integrity even as VCC decays toward 1 V-enabling robust reset signaling in low-voltage brown-out conditions common in industrial automation and renewable energy inverters.

Key Specifications

Pinout & Package

LM809M3X-4.63 is housed in a 3-pin SOT-23 (DBZ) package measuring 2.92 mm × 1.30 mm, optimized for high-density PCB layouts in space-constrained industrial and automotive control modules.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor reset applications.

Compared with MAX809TRD3-T and TPS3808G33DBVR, LM809M3X-4.63 delivers superior reset timing consistency (240 ms typical vs. 140 ms min), lower quiescent current (15 µA vs. 25 µA), and true pin-and-function compatibility in legacy SOT-23-3 layouts-making it optimal for industrial and automotive designs requiring proven reliability without layout change.

Availability

LM809M3X-4.63 is available at Aetrix Electronics and suitable for industrial PLC controllers, renewable energy inverters, factory automation HMIs, and automotive body control modules requiring stable component supply with long-term lifecycle support.

Supply support for LM809M3X-4.63 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

Texas Instruments is a global semiconductor leader delivering analog and embedded processing solutions, with over 50 years of innovation in power management, signal chain, and microcontroller technologies.

The LM809 product line was designed specifically for cost-sensitive, high-reliability microprocessor supervision in industrial, automotive, and computing applications-emphasizing precision threshold accuracy, wide temperature operation, and ultra-low power consumption.

FAQ

What is the exact reset threshold voltage of LM809M3X-4.63 and how does it vary with temperature?

The LM809M3X-4.63 has a nominal reset threshold of 4.63 V with ±3% tolerance at 25°C. Over the full operating range of –40°C to 105°C, the threshold varies from 4.40 V (min) to 4.86 V (max), corresponding to a temperature coefficient of 30 ppm/°C. This tight specification ensures predictable reset behavior in industrial environments where ambient temperature swings are common, and directly supports 5 V supply monitoring per JEDEC standards.

Does LM809M3X-4.63 provide a valid reset signal when VCC drops below 1 V?

No-LM809M3X-4.63 guarantees RESET output validity only for VCC ≥1 V. Below 1 V, the internal circuitry cannot maintain defined logic states, and the RESET output becomes high-impedance. To ensure deterministic behavior during deep brown-out, TI recommends adding a 100 kΩ pull-down resistor from RESET to GND, as documented in the LM809 datasheet Figure 7. This prevents floating states that could cause unintended microprocessor behavior.

What is the minimum and typical reset timeout duration for LM809M3X-4.63?

The LM809M3X-4.63 provides a minimum reset timeout of 140 ms and a typical value of 240 ms over –40°C to 85°C. At elevated temperatures (85°C to 105°C), the timeout extends up to 840 ms maximum. The 240 ms typical value ensures sufficient hold time for most microprocessors to complete power-on initialization, including PLL lock, memory self-test, and bootloader execution-making LM809M3X-4.63 suitable for ARM Cortex-M and legacy 8-bit µP platforms.

Can LM809M3X-4.63 be used with microprocessors that have bidirectional reset pins?

Yes-LM809M3X-4.63 can interface with bidirectional reset pins (e.g., Motorola 68HC11) using a 4.7 kΩ series resistor between the LM809M3X-4.63 RESET output and the µP reset pin, as shown in Figure 9 of the datasheet. This resistor isolates the LM809M3X-4.63 output driver from potential contention when the µP asserts its own reset signal, preventing damage and ensuring clean reset sequencing without requiring additional buffering.

What package type and marking code does LM809M3X-4.63 use?

LM809M3X-4.63 uses the SOT-23 (DBZ) package with 3 pins and a body size of 2.92 mm × 1.30 mm. Its top-side marking is "S8B", as confirmed in TI's orderable addendum. The "X" suffix denotes large tape-and-reel packaging (3000 units per reel), and "/NOPB.A" indicates lead-free, RoHS-compliant packaging with standard Sn finish and moisture sensitivity level 1 (260°C peak reflow).