Diodes Incorporated AP7381-33SA-7

Overview

AP7381-33SA-7 from Diodes Incorporated is a fixed-output 3.3V ultra-low dropout (ULDO) linear regulator IC designed for space-constrained portable and USB-powered systems. It delivers up to 150mA output current with 1000mV dropout at 100mA, ±2% output voltage accuracy, and only 2.5µA ground current at zero load - enabling long battery life in e-meters and handheld devices.

For engineers reviewing the AP7381-33SA-7 datasheet, AP7381-33SA-7 pinout, AP7381-33SA-7 application, or AP7381-33SA-7 equivalent, key selection criteria include wide 3.3V–40V input range compatibility, SOT23 package thermal performance, low-ESR ceramic capacitor support, and thermal shutdown/short-circuit protection behavior under transient load conditions.

Technical Context

The AP7381-33SA-7 integrates a precision voltage reference, error amplifier, resistor network for fixed 3.3V output, current-limit circuitry, and chip-enable logic. Its architecture supports stable regulation across -40°C to +125°C junction temperature with ±100ppm/°C output voltage drift.

It operates as a single-stage series pass regulator with internal thermal shutdown triggered at +160°C and hysteresis of +20°C. Line regulation is 0.05%/V and load regulation is 0.5% over 1–150mA, ensuring consistent output under varying source and load conditions.

Key Specifications

Pinout & Package

SOT23-3 package: compact 2.9mm × 1.3mm footprint with 0.95mm lead pitch; optimized for high-density PCB layouts and automated assembly. Moisture sensitivity level 1 per J-STD-020.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ULDO regulator applications.

Compared with MCP1700-3302E/TO and TPS7A2033PDBVR, the AP7381-33SA-7 uniquely balances 40V input capability, SOT23 size, and µA-level quiescent current - making it optimal for direct-battery-fed industrial and metering designs where pre-regulation adds cost and complexity.

Availability

AP7381-33SA-7 is available at Aetrix Electronics and suitable for smart metering, USB peripheral modules, and industrial sensor nodes requiring stable component supply with guaranteed long-term manufacturability and RoHS-compliant sourcing.

Supply support for AP7381-33SA-7 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 manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability power management, signal integrity, and protection solutions for industrial, computing, and consumer markets.

The AP7381 belongs to Diodes' wide-input ULDO regulator product line, engineered specifically for battery-backed and unregulated industrial power rails where input voltage can vary from near-output levels up to 40V.

FAQ

What is the minimum input voltage required for regulation at full 150mA load?

The AP7381-33SA-7 requires VIN ≥ VOUT + VDROP to maintain regulation. With VOUT = 3.3V and VDROP = 1000mV @ 100mA, the minimum VIN is 4.3V at 100mA. At 150mA, dropout increases slightly - datasheet shows ~1.1V typical, so minimum VIN is approximately 4.4V. Below this, output voltage drops linearly with input.

Can AP7381-33SA-7 operate with a 1µF input and 1µF output capacitor?

No. The datasheet specifies minimum 1µF input and 2.2µF output ceramic capacitors for stability and transient response. Using only 1µF on output risks oscillation and degraded load step recovery, especially under 100mA+ load changes. X5R/X7R dielectrics are mandatory; Y5V or Z5U types are not recommended.

Is thermal derating required for continuous 150mA operation in still air?

Yes. In a standard JEDEC 2-layer board, θJA for SOT23 is 167°C/W. At 150mA and 3.3V output with 12V input, power dissipation is (12V − 3.3V) × 0.15A ≈ 1.3W. This yields ΔT = 1.3W × 167°C/W ≈ 217°C rise - exceeding the +125°C max TJ. Derating to ≤50mA or adding copper pour/thermal vias is required for sustained operation.

Does AP7381-33SA-7 include an enable pin or power-good indicator?

No. The AP7381-33SA-7 has no enable (EN) or power-good (PG) pin. It operates continuously when VIN is within specification. For controlled startup sequencing, external circuitry (e.g., MOSFET gate driver tied to system controller) must be used - unlike some Diodes regulators such as AP2204K, which include active-high EN functionality.