Renesas RNA51958AFP#H0

Overview

RNA51958AFP#H0 from Renesas Electronics is a voltage-detecting system reset IC with adjustable detection threshold (1.25 V typical), 2–17 V supply range, and external capacitor-controlled delay (e.g., ~100 ms at 0.33 µF). It features open-collector output, 15 mV hysteresis, and operates in CPU/microcontroller reset circuits for embedded power management.

For engineers reviewing the RNA51958AFP#H0 datasheet, RNA51958AFP#H0 pinout, RNA51958AFP#H0 application, or RNA51958AFP#H0 equivalent, key selection factors include externally programmable reset voltage via resistor divider, temperature-stable 0.01 %/°C detection coefficient, low 360 µA typical supply current, and SOP-8 package compatibility with industrial-grade –40 to +85 °C operation.

Technical Context

The RNA51958AFP#H0 implements a precision bandgap-based voltage comparator with 1.25 V reference and 15 mV hysteresis to prevent chatter during threshold crossing. Its delay timing is generated by charging an external capacitor through a constant-current source (–5 µA typical), enabling predictable, resistor-free time control.

It supports two primary configurations: supply-voltage monitoring (via resistor divider on Input pin) and independent signal reset (e.g., logic pulse or transistor-driven input), with design constraints on input voltage range (0.8 V to VCC–0.3 V) and absolute max ratings (18 V supply, –0.3 V to +7 V input).

Key Specifications

Pinout & Package

RNA51958AFP#H0 is housed in an 8-pin SOP package (JEITA PRSP0008DE-C, 4.4 mm × 4.85 mm, 1.27 mm pitch) with Ni/Pd/Au plating and 2,500 pcs/reel taping.

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, RNA51958AFP#H0 provides unique adjustability of both detection voltage and delay time via passive components - enabling one-footprint support for multiple supply rails and timing requirements while maintaining industrial temperature rating and open-collector flexibility.

Availability

RNA51958AFP#H0 is available at Aetrix Electronics and suitable for microcontroller reset, battery monitoring, DC/DC sequencing, and waveform shaping applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for RNA51958AFP#H0 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 is a Japanese semiconductor manufacturer specializing in microcontrollers, analog, and power management ICs for industrial, automotive, and infrastructure markets.

The RNA51958 series belongs to Renesas' voltage supervisor and system reset product line, designed specifically for reliable, low-cost, and field-configurable power-on reset and brownout detection in resource-constrained embedded systems.

FAQ

What is the detection voltage accuracy and temperature stability of RNA51958AFP#H0?

The RNA51958AFP#H0 has a typical detection voltage of 1.25 V with ±0.05 V (1.20–1.30 V) tolerance at 25 °C and a temperature coefficient of 0.01 %/°C. This ensures detection voltage drift remains within ±0.6% over the full –40 to +85 °C operating range, making RNA51958AFP#H0 suitable for environments with significant thermal variation without calibration.

How do I calculate the external resistor values for a custom detection voltage with RNA51958AFP#H0?

To set a target detection voltage V_DET, use R1 and R2 in a divider from VCC to GND, with RNA51958AFP#H0 Input (Pin 2) connected to the midpoint. The formula is V_DET ≈ 1.25 V × (R1 + R2)/R2. For example, for V_DET = 4.5 V, choose R2 = 100 kΩ and R1 ≈ 260 kΩ. Keep total resistance ≤1 MΩ to limit error from 100 nA input current, as specified in the RNA51958AFP#H0 datasheet.

What is the maximum allowable delay capacitor value for RNA51958AFP#H0, and why is there a limit?

The RNA51958AFP#H0 datasheet specifies a maximum delay capacitor (Cd) of 10 µF. Larger values cause three issues: (1) increased delay time variation (e.g., 100 µF yields 16–70 s instead of nominal 34 s), (2) degraded response to momentary voltage dips (t_PHL rises to ~200 µs), and (3) failure to fully discharge between events, corrupting timing accuracy. Staying within 10 µF ensures predictable, repeatable behavior per RNA51958AFP#H0 specifications.

Can RNA51958AFP#H0 monitor a voltage rail higher than its own VCC supply?

No - RNA51958AFP#H0 Input (Pin 2) voltage must stay within –0.3 V to VCC–0.3 V when VCC ≤ 7 V, or –0.3 V to +7.0 V when VCC > 7 V. To monitor a higher rail (e.g., 12 V), use a resistor divider that scales it into this range. Direct connection risks exceeding absolute maximum input ratings and damaging the RNA51958AFP#H0 device.

Does RNA51958AFP#H0 require a bypass capacitor on its VCC pin, and what value is recommended?

Yes - the RNA51958AFP#H0 datasheet recommends installing both low-frequency (C1, e.g., 10 µF tantalum) and high-frequency (C2, e.g., 0.1 µF ceramic) bypass capacitors between VCC (Pin 8) and GND (Pin 3). This suppresses ripple and noise that could cause false resets. Layout best practice is to place C2 within 5 mm of the pins and route GND with low inductance, as outlined in the RNA51958AFP#H0 application notes.