onsemi KA75420ZBU

Overview

KA75420ZBU from Fairchild Semiconductor is a fixed-threshold voltage detector IC designed for microprocessor reset supervision, with a precise 4.2 V detection voltage, ±0.01 %/°C temperature coefficient, 50 mV hysteresis, and operation from −25 °C to +85 °C. It delivers 20 mA output sink current at on-time and consumes only 30–50 µA quiescent current in off-state, used in embedded power-on reset circuits.

For engineers reviewing the KA75420ZBU datasheet, pinout, applications, or equivalent options, key selection criteria include detection threshold accuracy, hysteresis margin, low quiescent current, TO-92/SOT-89 package compatibility, and reset timing delay (0.6–10 µs low-to-high, 15–20 µs high-to-low).

Technical Context

The KA75420ZBU integrates a precision bandgap reference, comparator, and open-drain NMOS output stage. Its internal hysteresis of 50 mV prevents oscillation during slow-rising or noisy supply transitions, and its threshold operating voltage of 0.8–1.0 V enables reliable detection even under brown-out conditions.

It operates without external components-only requiring a pull-up resistor on the output-and supports direct interface to CMOS/TTL reset inputs. The device asserts an active-low reset signal when V_CC falls below 4.2 V and releases it after V_CC rises above 4.25 V (4.2 V + 50 mV hysteresis).

Key Specifications

Pinout & Package

KA75420ZBU is supplied in TO-92 package (3-lead plastic transistor outline), with standardized pinout: Pin 1 = Input (V_CC), Pin 2 = GND, Pin 3 = Output (open-drain). Mechanical dimensions conform to JEDEC TO-92 standard (14.47 mm length, 4.58 mm width, 3.60 mm height).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage detector applications.

Compared with TLV803EB29DBZR and MAX809SEUR+T, the KA75420ZBU provides higher detection voltage (4.2 V), integrated 50 mV hysteresis, and TO-92 compatibility-making it optimal for legacy 5 V designs where board space and thermal dissipation allow larger packages.

Availability

KA75420ZBU is available at Aetrix Electronics and suitable for microcontroller reset, battery supervision, industrial PLC modules, and legacy embedded system brown-out protection requiring stable component supply and long-term obsolescence management.

Supply support for KA75420ZBU 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

Fairchild Semiconductor was a U.S.-based analog and power IC manufacturer, acquired by ON Semiconductor in 2016; its legacy products remain widely deployed in industrial and automotive systems.

The KA75XXX series was developed specifically for cost-sensitive, high-reliability voltage monitoring in microprocessor-based equipment-emphasizing simplicity, low power, and robustness over programmability or multi-threshold flexibility.

FAQ

What is the exact detection voltage of KA75420ZBU and how tightly is it specified?

The KA75420ZBU has a nominal detection voltage of 4.2 V, with a guaranteed range of 4.05 V to 4.35 V at 25 °C. This specification is confirmed in the Electrical Characteristics table of the official Fairchild datasheet Rev. 1.0.3, and applies directly to the KA75420ZBU variant within the KA75XXX family.

Does KA75420ZBU require external components to function?

No, KA75420ZBU operates autonomously with only an external pull-up resistor on its open-drain output pin. No capacitors, resistors, or feedback networks are needed-its internal hysteresis, reference, and comparator are fully integrated, making KA75420ZBU a true 3-pin "set-and-forget" reset supervisor.

What package options are available for KA75420ZBU and how do they differ electrically?

The KA75420ZBU is offered in TO-92 (suffix Z) and SOT-89 (suffix M) packages. Both share identical electrical specifications-including 4.2 V detection, 50 mV hysteresis, and 20 mA sink current-but differ thermally: TO-92 has 200 mW power dissipation, SOT-89 supports 500 mW, enabling higher ambient operation in compact layouts.

Can KA75420ZBU be used in automotive applications?

The KA75420ZBU is rated for −25 °C to +85 °C operation and was historically used in automotive body electronics (e.g., infotainment power sequencing). However, it is not AEC-Q100 qualified, so KA75420ZBU should only be deployed in non-safety-critical automotive subsystems where extended temperature validation is performed by the end designer.

How does the hysteresis of KA75420ZBU prevent false resets?

The KA75420ZBU incorporates 50 mV of built-in hysteresis: it asserts reset at 4.2 V but does not release until V_CC rises to 4.25 V. This 50 mV window rejects noise spikes and slow supply recoveries that could otherwise cause oscillatory reset behavior-ensuring KA75420ZBU delivers a clean, single-pulse reset event per power cycle.