Renesas M51945AFP#CF0R

Overview

M51945AFP#CF0R from Renesas Electronics is a low-power voltage-detecting system reset IC with open-collector output (Type B), designed for microcontroller and logic circuit reset supervision. It features a 1.25 V internal reference, 15 mV typical hysteresis, 2–17 V supply range, and supports external resistor-based detection voltage setting from 2 V to 15 V. It is used in battery-check circuits, DC/DC converter monitoring, and CPU reset applications.

For engineers reviewing the M51945AFP#CF0R datasheet, M51945AFP#CF0R pinout, M51945AFP#CF0R application, or M51945AFP#CF0R equivalent, key selection criteria include its L-reset polarity, 280 µA typical circuit current at 5 V, 0.2 V typical output saturation voltage, –30°C to +85°C operating temperature, and SIP-5 package compatibility with legacy industrial control designs.

Technical Context

The M51945AFP#CF0R 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 a low-active reset signal when the input falls below the threshold.

As an "L reset type" device, it asserts a logic-low output during undervoltage conditions. The open-collector output requires an external pull-up resistor and supports sink currents up to 4 mA, enabling flexible interfacing with TTL, CMOS, and microcontroller reset inputs across diverse supply domains.

Key Specifications

Pinout & Package

Package: 5-pin SIP (SIP5-P-240-2.54, EIAJ code 5P5T), plastic single-in-line, 2.54 mm pitch, 11.9 mm × 2.54 mm footprint, lead-free Cu alloy leads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with M51945AFP#CF0R, APX803S-33SA-7 offers smaller footprint but sacrifices voltage programmability, while TPS3808G33DBVR delivers superior current efficiency yet introduces additional external components and timing dependencies not present in the M51945AFP#CF0R's simple 2-resistor configuration.

Availability

M51945AFP#CF0R is available at Aetrix Electronics and suitable for industrial control panels, legacy embedded instrumentation, and battery-backed memory systems requiring stable component supply and long-term obsolescence management.

Supply support for M51945AFP#CF0R 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 formed in 2010 through the merger of NEC Electronics and Renesas Technology, specializing in microcontrollers, analog, and power solutions.

The M51945AFP#CF0R belongs to Renesas' legacy Voltage Detecting, System Resetting IC Series, engineered for robust, low-cost reset supervision in cost-sensitive industrial and consumer electronics where programmable detection thresholds and wide supply tolerance are critical.

FAQ

What is the reset polarity and output configuration of the M51945AFP#CF0R?

The M51945AFP#CF0R is an "L reset type" IC with active-low reset assertion and an open-collector (Type B) output. When the monitored voltage falls below the detection threshold, the output pulls low (sinks current). The M51945AFP#CF0R requires an external pull-up resistor to define the high-state voltage level, enabling interface flexibility with various logic families and voltage domains.

How is the detection voltage set for the M51945AFP#CF0R?

The M51945AFP#CF0R uses an internal 1.25 V reference and accepts an externally divided input voltage. Detection voltage VS is calculated as VS ≈ 1.25 × (R1 + R2)/R2, where R1 and R2 form a resistor divider from VCC to GND, with the divider midpoint connected to the Input pin (Pin 2). The M51945AFP#CF0R supports setting VS between 2 V and 15 V, with design attention required to minimize error from input bias current (100 nA typ).

What package type and pin compatibility does the M51945AFP#CF0R use?

The M51945AFP#CF0R is packaged in a 5-pin SIP (Single In-line Package) with EIAJ code 5P5T and outline SIP5-P-240-2.54. It shares pinout compatibility with other members of the M51945A/B family in the same SIP-5 variant, including identical Pin 1 (GND), Pin 2 (Input), Pin 3 (VCC), Pin 4 (Output), and Pin 5 (NC). This allows direct replacement within legacy SIP-5 footprint designs.

What is the minimum supply voltage required for the M51945AFP#CF0R to operate correctly?

The M51945AFP#CF0R has a threshold operating voltage (VOPL) of 0.55 V (typical) at RL = 2.2 kΩ, meaning it can maintain functional reset behavior even as the supply voltage drops close to 0.6 V. This ultra-low VOPL enables reliable brownout detection in battery-powered systems nearing end-of-life, ensuring the M51945AFP#CF0R remains active longer than many competing reset ICs before losing regulation.

Is the M51945AFP#CF0R recommended for new designs?

No - the M51945AFP#CF0R is marked "Not recommend for new design" in the official Renesas documentation (REJ03D0774-0300 Rev.3.00). While fully functional and supported for existing production, Renesas advises migrating new designs to newer-generation reset ICs offering improved accuracy, lower current, extended temperature range, or enhanced reliability features. The M51945AFP#CF0R remains viable for legacy repair, continuity builds, and long-lifecycle industrial maintenance.