Renesas M51945BL#TF0J

Overview

M51945BL#TF0J from Renesas Electronics is an L-reset-type voltage-detecting system reset IC with open-collector output, designed for reliable power-on and brownout reset generation in microcontroller-based systems. It features a 1.25 V internal reference, 15 mV typical hysteresis, 2–17 V supply range, and supports external resistor-programmable detection thresholds down to 2 V. It is used in CPU/MCU reset circuits where low-threshold operation and noise immunity are critical.

For engineers reviewing the M51945BL#TF0J datasheet, M51945BL#TF0J pinout, M51945BL#TF0J application, or M51945BL#TF0J equivalent, key selection considerations include its open-collector output configuration, –30°C to +85°C operating temperature range, 0.55 V typical threshold operating voltage at RL = 100 kΩ, and compatibility with legacy 8-pin SOP (PRSP0008DE-C) packaging.

Technical Context

The M51945BL#TF0J implements a precision comparator architecture with a stable 1.25 V bandgap reference and 25 µA typical input bias current. Its internal hysteresis (9–23 mV) prevents oscillation during slow-rising or noisy supply transitions.

As an "L reset" device, it asserts an active-low reset signal when the monitored input voltage falls below the programmed threshold. The open-collector output allows flexible pull-up configuration and level translation across different logic families and supply domains.

Key Specifications

Pinout & Package

Package: PRSP0008DE-C - 8-pin SOP (4.4 mm × 4.85 mm, 1.27 mm pitch), recommended for new designs per Renesas documentation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage-detecting reset applications.

Compared with TLV803EB29DBZR and MAX809SEUR+T, the M51945BL#TF0J offers programmable threshold and wider supply range but requires larger SOP8 layout; neither alternative supports resistor-based voltage setting or 17 V operation.

Availability

M51945BL#TF0J is available at Aetrix Electronics and suitable for industrial control systems, battery-powered instrumentation, and embedded MCU platforms requiring stable component supply and long-term lifecycle support.

Supply support for M51945BL#TF0J 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

Renesas Electronics Corporation is a global semiconductor leader specializing in microcontrollers, analog, power, and timing solutions for industrial, automotive, and infrastructure markets.

The M51945BL#TF0J belongs to Renesas' legacy Voltage Detecting, System Resetting IC Series, engineered for cost-sensitive, reliability-critical reset supervision in non-automotive industrial and consumer electronics.

FAQ

What is the function of the M51945BL#TF0J in a microcontroller system?

The M51945BL#TF0J serves as a precision voltage-monitoring reset generator that asserts an active-low reset signal when the monitored supply voltage falls below a user-programmed threshold. In a microcontroller system, it ensures deterministic startup and safe recovery from brownout conditions by holding the MCU in reset until VCC exceeds the detection voltage plus hysteresis. Its open-collector output allows integration into shared reset buses, and its 1.25 V internal reference enables accurate, temperature-stable threshold setting via external resistors - a core capability of the M51945BL#TF0J.

How do I calculate the detection voltage for the M51945BL#TF0J?

The detection voltage VS for the M51945BL#TF0J is calculated as VS ≈ 1.25 V × (R1 + R2) / R2, where R1 connects between VCC and the Input pin (pin 2), and R2 connects between Input and GND. Input current (100 nA typ) introduces small error; use R1 + R2 ≤ 200 kΩ to limit error to <1%. For example, R1 = 180 kΩ and R2 = 30 kΩ yields VS ≈ 8.75 V. This resistor-based programming is a defining feature of the M51945BL#TF0J and enables flexible threshold configuration without changing the IC.

What is the difference between M51945BL#TF0J and M51945AL#TF0J?

The M51945BL#TF0J features an open-collector output (Type B), requiring an external pull-up resistor to define the high-state voltage and enable wired-OR reset bus configurations. In contrast, the M51945AL#TF0J has a built-in load (Type A) and drives high actively, simplifying design but limiting interface flexibility. Both share identical detection characteristics, hysteresis, and supply range. The "B" suffix in M51945BL#TF0J explicitly denotes this open-collector functionality - a critical distinction affecting schematic implementation and system-level reset architecture.

Is the M51945BL#TF0J suitable for new designs?

Renesas documentation explicitly states "Not recommend for new design" for the PRSP0008DA-A (8P2S-A) variant, but confirms PRSP0008DE-C as the recommended 8-pin SOP package for the M51945BL#TF0J. While the device remains available and functional, Renesas positions it as a mature product. New designs should verify long-term availability with Aetrix Electronics and consider modern alternatives if extended 15+ year support or enhanced features (e.g., watchdog, manual reset) are required. The M51945BL#TF0J itself is fully specified and supported for industrial applications within its quality grade.

What are the absolute maximum ratings for the M51945BL#TF0J?

The absolute maximum ratings for the M51945BL#TF0J are: supply voltage (VCC) = 18 V, output sink current = 6 mA, output voltage (VO) = 18 V (open-collector), operating temperature = –30°C to +85°C, and storage temperature = –40°C to +125°C. Exceeding VCC = 18 V or sink current = 6 mA risks permanent damage. The 1.25 V internal reference and comparator inputs are rated for –0.3 V to VCC (≤7 V) or –0.3 V to +7 V (VCC >7 V). These limits define the safe operational envelope of the M51945BL#TF0J and must be respected in all PCB layouts and system power sequencing.