Renesas M51945AFP#DF0R

Overview

M51945AFP#DF0R from Renesas Electronics is an L-type (active-low) voltage-detecting system reset IC with adjustable detection threshold via external resistors, designed for CPU/microcontroller power-on and brownout reset generation in embedded logic systems. It operates across 2 V to 17 V supply, features 1.25 V internal reference, 15 mV typical hysteresis, and low 280 µA circuit current at 5 V.

For engineers reviewing the M51945AFP#DF0R datasheet, M51945AFP#DF0R pinout, M51945AFP#DF0R application, or M51945AFP#DF0R equivalent, key selection criteria include its open-collector output configuration, –30°C to +85°C operating range, 0.55 V typical threshold operating voltage, and compatibility with battery-check, level-detect, and waveform-shaping circuits requiring precise reset assertion.

Technical Context

The M51945AFP#DF0R implements a precision comparator architecture with a stable 1.25 V bandgap reference and 25 µA input bias current, enabling accurate voltage monitoring independent of supply rail fluctuations. Its detection threshold is externally programmable using two resistors (R1, R2), yielding VS ≈ 1.25 × (R1 + R2)/R2 over 2–15 V range.

As an "L" reset type device, it asserts a low-level active output when input voltage falls below the programmed threshold, with 4 µs typical propagation delay on power-down and 2 µs on power-up. The open-collector output requires an external pull-up resistor and supports sink currents up to 4 mA while maintaining ≤0.4 V saturation voltage.

Key Specifications

Pinout & Package

Package: 5-pin SIP (SIP5-P-240-2.54 / 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#DF0R, APX803S-43SA-7 offers lower power and smaller footprint but no adjustability, while TPS3808G12DBVR delivers superior accuracy and hysteresis control at the expense of minimum operating voltage margin and higher cost.

Availability

M51945AFP#DF0R is available at Aetrix Electronics and suitable for battery-check circuits, microcontroller reset generation, and DC/DC converter protection requiring stable component supply across extended temperature ranges and long-lifecycle industrial programs.

Supply support for M51945AFP#DF0R 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 formed in 2010 through merger of NEC Electronics and Renesas Technology, specializing in microcontrollers, analog, and power management ICs.

The M51945AFP#DF0R belongs to Renesas' legacy Voltage Detecting, System Resetting IC Series, designed specifically for robust, low-cost reset supervision in cost-sensitive industrial and consumer electronics where external threshold adjustment and wide supply tolerance are critical.

FAQ

What is the function of the NC pin on the M51945AFP#DF0R?

Pin 5 of the M51945AFP#DF0R is designated NC (No Connection) and must remain unconnected in PCB layout. This terminal has no internal bond wire or circuit connection; routing traces or applying solder to it may cause unpredictable behavior or damage. The datasheet explicitly states NC pins are electrically and physically isolated from all internal functions of the M51945AFP#DF0R.

Can the M51945AFP#DF0R detect voltages below 2 V?

No, the M51945AFP#DF0R cannot reliably detect voltages below 2 V. Its specified supply voltage range is 2 V to 17 V, and the minimum detection voltage is constrained by the 1.25 V internal reference and required headroom for comparator operation. While the device can operate down to 0.55 V supply (threshold operating voltage), input detection remains limited to ≥2 V per the recommended operating conditions and electrical characteristics table in the official Renesas datasheet for M51945AFP#DF0R.

How do I calculate the external resistor values for a 3.3 V reset threshold using M51945AFP#DF0R?

To set a 3.3 V detection threshold with the M51945AFP#DF0R, use the formula VS ≈ 1.25 × (R1 + R2)/R2. Solving for R1/R2 = (3.3/1.25) − 1 ≈ 1.64 yields R1 = 164 kΩ and R2 = 100 kΩ as a standard-value pair. Ensure total resistance stays below 100 kΩ to minimize error from 100 nA input current; verify actual threshold with bench measurement, as the M51945AFP#DF0R's ±5% detecting voltage tolerance and 15 mV hysteresis affect final accuracy.

Is the M51945AFP#DF0R pin-compatible with the M51945AL variant?

No, the M51945AFP#DF0R is not pin-compatible with the M51945AL. The M51945AFP#DF0R uses a 5-pin SIP package (5P5T) with pinout GND–Input–VCC–Output–NC, whereas the M51945AL uses an 8-pin SOP package (PRSP0008DE-C) with different pin assignment and spacing. The datasheet explicitly separates their outline drawings and thermal derating curves, confirming distinct mechanical and electrical integration requirements for each M51945AFP#DF0R and M51945AL variant.

Does the M51945AFP#DF0R support high-temperature operation beyond +85°C?

No, the M51945AFP#DF0R is rated for operation only from –30°C to +85°C. The Absolute Maximum Ratings table specifies +85°C as the upper limit for Topr (operating temperature), and the Typical Characteristics graphs (e.g., detection voltage vs. ambient temperature) are validated only within this range. Using the M51945AFP#DF0R above +85°C violates its qualified operating conditions and may result in parametric shift, increased failure rate, or functional failure without warning.