onsemi KA75420ZTA

Overview

KA75420ZTA from Fairchild Semiconductor is a fixed-threshold voltage detector IC designed for microprocessor reset supervision, with 4.2 V detection threshold, 50 mV hysteresis, ±0.01 %/°C temperature coefficient, and TO-92 package. It monitors supply rails in embedded controllers to prevent erroneous operation during power-up/down and low-battery conditions.

For engineers reviewing the KA75420ZTA datasheet, pinout, applications, or equivalent options, key selection criteria include detection accuracy over temperature, output drive capability (20 mA sink), ultra-low quiescent current in off-state (30–50 µA), and compatibility with standard 5 V or 3.3 V logic reset inputs.

Technical Context

The KA75420ZTA implements a precision bandgap-based voltage reference and comparator with internal hysteresis to reject noise-induced false triggers. Its output is an open-drain N-channel MOSFET that pulls low when V_IN falls below 4.2 V (typ), enabling direct interface to µP RESET pins without external pull-up resistors in many configurations.

It operates across -25°C to +85°C with <±0.01 %/°C V_DET drift and maintains valid reset assertion down to V_CC = 0.8 V (threshold operating voltage), ensuring reliable behavior even during brown-out recovery.

Key Specifications

Pinout & Package

KA75420ZTA is supplied in TO-92 package (3-pin plastic transistor outline), with lead spacing 1.27 mm, body height 3.60 mm, and standardized pin assignment per Fairchild mechanical drawing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV803EB29DBZR and APX803S-42SA-7, the KA75420ZTA offers higher output drive (20 mA vs ≤5 mA), TO-92 through-hole compatibility for legacy manufacturing, and proven thermal stability in industrial ambient ranges-making it preferred for cost-sensitive, non-ultra-low-power 5 V reset applications.

Availability

KA75420ZTA is available at Aetrix Electronics and suitable for microcontroller reset supervision, battery voltage monitoring, brown-out protection, and industrial PLC I/O module design requiring stable component supply and long-term obsolescence management.

Supply support for KA75420ZTA 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-effective, high-reliability power-supply monitoring in embedded control applications where precision, simplicity, and through-hole manufacturability were prioritized.

FAQ

What is the detection voltage tolerance for KA75420ZTA?

The KA75420ZTA has a detection voltage of 4.2 V (typical), with a guaranteed range of 4.05 V to 4.35 V at TA = 25°C. This ±0.15 V tolerance ensures robust reset activation across process variation while maintaining compatibility with standard 5 V logic thresholds. The KA75420ZTA's tight specification supports reliable operation in industrial environments where supply rails may exhibit minor deviations.

Does KA75420ZTA require an external pull-up resistor on its output?

Yes, KA75420ZTA features an open-drain output and requires an external pull-up resistor to define the high-level voltage and provide current path during reset assertion. Typical values range from 4.7 kΩ to 10 kΩ to 3.3 V or 5 V. The KA75420ZTA's 20 mA sink capability ensures compatibility with common logic families without additional buffering.

What is the minimum supply voltage at which KA75420ZTA remains functional?

The KA75420ZTA maintains valid reset assertion down to a supply voltage of 0.8 V (V_TH(OPR)), enabling reliable brown-out detection even as the main rail collapses. This behavior is specified under RL = 200 Ω with VOL ≤ 0.4 V. The KA75420ZTA leverages this low-voltage operation to ensure system safety during deep undervoltage events.

How does hysteresis improve performance in KA75420ZTA?

The KA75420ZTA integrates 50 mV (typical) hysteresis to prevent output chatter during slow or noisy supply transitions near the 4.2 V threshold. This eliminates need for external RC filtering and guarantees monotonic reset deassertion. In real-world applications like motor-driven systems, the KA75420ZTA's hysteresis prevents spurious resets caused by supply ripple or inrush transients.

Is KA75420ZTA compatible with SOT-89 footprint?

No, KA75420ZTA is packaged exclusively in TO-92 (ZTA suffix denotes TO-92). The SOT-89 variant of the same detection voltage is KA75420M. While both share identical electrical specifications, their footprints, thermal performance (PD = 200 mW vs 500 mW), and mounting methods differ. KA75420ZTA must be placed in TO-92 land patterns and cannot be substituted with KA75420M without PCB revision.