Diodes Incorporated ZLDO500T8TC

Overview

ZLDO500T8TC from Diodes Incorporated (formerly Zetex) is an ultra-low-dropout linear regulator delivering a fixed 5.0 V output at up to 300 mA, with dropout as low as 6 mV at 10 mA and 30 mV at 100 mA. It integrates a low-battery flag (open-collector LBF), active-high shutdown control, and thermal shutdown - enabling precise power management in space-constrained, battery-powered systems such as palmtop computers and portable instrumentation.

For engineers reviewing the ZLDO500T8TC datasheet, ZLDO500T8TC pinout, ZLDO500T8TC application, or ZLDO500T8TC equivalent, key selection criteria include its 300 mA output capability, 1 mA quiescent current under full load, 200 mV low-battery detection threshold, shutdown current of 11 µA, and SM8 surface-mount package compatibility with high-density PCB layouts.

Technical Context

The ZLDO500T8TC employs a precision bandgap reference and error amplifier with external shaping capacitor (10 pF from Pin 8 to Pin 5) to ensure stability across load and temperature. Its dropout behavior is defined by a PNP pass transistor architecture optimized for minimal Vin–Vout differential.

Low-battery detection uses an internal comparator referenced to VOUT + 200 mV, pulling the open-collector LBF pin low when input falls within that margin. Shutdown control (Pin 2) is TTL/CMOS-compatible with ≤10 µA input current and 1.5 V turn-on threshold, disabling regulation and reducing I_Q to 11 µA typical.

Key Specifications

Pinout & Package

Package: SM8 (8-pin small-outline surface-mount), 4.9 mm × 6.0 mm body, 1.27 mm pitch, gull-wing leads. Designed for high thermal dissipation on 2-inch² PCBs (2 W max at Tamb = 25°C).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-low-dropout 5 V regulator applications.

Compared with MCP1700T-5002E/MB and NCP1117ST50T3G, the ZLDO500T8TC uniquely combines sub-30 mV dropout at light loads, integrated LBF signaling, and 11 µA shutdown - making it irreplaceable in battery-aware portable designs requiring both precision regulation and predictive power management.

Availability

ZLDO500T8TC is available at Aetrix Electronics and suitable for portable medical sensors, industrial handheld terminals, and smart meter backup power systems requiring stable component supply with long-term lifecycle visibility.

Supply support for ZLDO500T8TC 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

Diodes Incorporated is a global semiconductor company specializing in discrete, analog, and mixed-signal solutions for power management, signal integrity, and connectivity applications.

The ZLDO series was developed by Zetex (acquired by Diodes Inc. in 2008) specifically for ultra-low-power, battery-critical applications demanding sub-100 mV dropout, integrated fault signaling, and compact SM8 packaging.

FAQ

What is the minimum input voltage required for regulation at 300 mA output?

The ZLDO500T8TC maintains regulation as long as VIN ≥ VOUT + dropout voltage. At 300 mA, typical dropout is 100 mV, so minimum VIN = 5.0 V + 0.1 V = 5.1 V. Absolute minimum per datasheet is VIN ≥ VOUT + 0.2 V to guarantee LBF assertion before dropout.

Can Pin 6 (D/C) be grounded or left unconnected safely?

Pin 6 (D/C) is internally wired to a sensitive circuit node and must remain unconnected - neither grounded nor tied to any other net. Doing so may cause regulation instability, excessive quiescent current, or thermal shutdown due to unintended biasing of internal circuitry.

How does the 10 pF shaping capacitor affect stability and transient response?

The 10 pF capacitor from Pin 8 (SPG) to Pin 5 (VOUT) sets the dominant pole of the error amplifier. Reducing it improves load transient response but risks oscillation under heavy or capacitive loads; increasing it degrades AC performance but enhances phase margin. The 10 pF value is optimized for ≥1 µF output capacitance and all specified load conditions.

Is the ZLDO500T8TC recommended for new designs?

No - the official datasheet states "ZLDO500 IS NOT RECOMMENDED FOR NEW DESIGNS." It remains available for legacy support and existing production, but Diodes Incorporated recommends newer alternatives like the AP2204K-5.0 or AP7361-C for new projects due to improved PSRR, lower I_Q, and extended temperature range.