Renesas M51945BFP#TF0R

Overview

M51945BFP#TF0R from Renesas Electronics is an L-reset-type voltage-detecting system reset IC with open-collector output, designed for monitoring supply rails and asserting active-low reset signals to microcontrollers and logic circuits. It features a 1.25 V internal reference, 15 mV typical hysteresis, 2–17 V supply range, and supports external resistor-based threshold setting from 2 V to 15 V. It is used in embedded power-on reset and brownout detection circuits.

For engineers reviewing the M51945BFP#TF0R datasheet, M51945BFP#TF0R pinout, M51945BFP#TF0R application, or M51945BFP#TF0R equivalent, key selection criteria include its low-threshold operating voltage (0.55 V typ), open-collector output compatibility with mixed-voltage systems, wide temperature range (–30°C to +85°C), and SIP-5 package suitability for space-constrained industrial control PCBs.

Technical Context

The M51945BFP#TF0R implements a precision comparator architecture with a stable 1.25 V bandgap reference and 25 µA internal bias current. Its input stage monitors an externally divided supply voltage, triggering reset assertion when the scaled input falls below the reference.

As an "L" reset type device, it drives its open-collector output low during fault conditions (undervoltage), requiring an external pull-up resistor. Propagation delay is 4 µs (H→L) and 2 µs (L→H), enabling fast response to supply transients without excessive noise sensitivity.

Key Specifications

Pinout & Package

Package: 5-pin SIP (5P5T), plastic single-in-line, 2.54 mm pitch, 11.9 mm × 2.54 mm footprint, lead material Cu alloy with Ni/Pd/Au plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with M51945BFP#TF0R, TLV803EB29DBZR and MAX6326LT29D3+T offer higher accuracy and smaller packages but eliminate external threshold flexibility and SIP-5 mechanical compatibility-making them unsuitable as drop-in replacements in legacy industrial control modules.

Availability

M51945BFP#TF0R is available at Aetrix Electronics and suitable for industrial control systems, battery-powered instrumentation, and embedded microcontroller reset circuits requiring stable component supply across extended product lifecycles.

Supply support for M51945BFP#TF0R 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 Japanese semiconductor manufacturer specializing in microcontrollers, analog and power devices, and system-on-chip solutions for industrial, automotive, and infrastructure markets.

The M51945BFP#TF0R belongs to Renesas' legacy Voltage Detecting, System Resetting IC Series, designed specifically for cost-sensitive, high-reliability embedded reset supervision where programmable thresholds and wide supply range are essential.

FAQ

What is the function of the NC pin on the M51945BFP#TF0R?

The NC (No Connection) pin on the M51945BFP#TF0R is internally unconnected and must remain floating or be tied to GND per Renesas design guidance. It serves no electrical function and is retained for mechanical compatibility with the 5-pin SIP package outline. Leaving it unconnected does not affect M51945BFP#TF0R operation, but grounding it improves noise immunity in high-EMI environments without risk of shorting.

Can the M51945BFP#TF0R be used with a 3.3 V logic system?

Yes, the M51945BFP#TF0R can interface directly with 3.3 V logic systems via its open-collector output, provided the external pull-up resistor connects to the 3.3 V rail. Its input stage operates correctly with VCC = 3.3 V, and its 1.25 V internal reference enables accurate threshold setting-for example, a 3.3 V reset point is achieved using R1 = 162 kΩ and R2 = 100 kΩ. The M51945BFP#TF0R's 2–17 V supply range fully covers 3.3 V operation.

What is the maximum allowable output sink current for the M51945BFP#TF0R?

The absolute maximum output sink current for the M51945BFP#TF0R is 6 mA, but Renesas specifies 4 mA as the recommended maximum for reliable long-term operation. Exceeding 4 mA increases V_sat beyond 0.4 V and risks thermal overstress, especially at elevated ambient temperatures. For a 3.3 V pull-up, a minimum RL of 825 Ω ensures compliance; the M51945BFP#TF0R datasheet confirms 4 mA sink capability at V_sat ≤ 0.4 V with VCC = 5 V.

How does the hysteresis of the M51945BFP#TF0R prevent reset chatter?

The M51945BFP#TF0R incorporates 15 mV typical hysteresis between its detect and release thresholds-e.g., trips at 1.25 V but releases at ~1.265 V. This built-in offset prevents oscillatory reset toggling when the monitored supply voltage lingers near the trip point due to ripple or slow recovery. The hysteresis is internal and fixed, eliminating need for external positive feedback components and ensuring consistent behavior across temperature (–30°C to +85°C) and unit-to-unit variation.

Is the M51945BFP#TF0R suitable for new designs?

No-the M51945BFP#TF0R is explicitly marked "Not recommend for new design" in Renesas documentation due to obsolescence status and lack of active roadmap support. While fully functional and available through authorized channels, Renesas recommends migrating to newer reset IC families such as the ISL8011x or RA4M2-based integrated supervision for new projects. Existing designs using M51945BFP#TF0R remain supported for maintenance and replacement.