Diodes Incorporated AP7315D-18FS4-7B

Overview

AP7315D-18FS4-7B from Diodes Incorporated is a 150mA, 1.8V fixed-output low-dropout linear regulator with integrated auto-discharge function, ±1% output voltage accuracy, 75dB PSRR at 1kHz, and 60µV_rms output noise (10Hz–100kHz). It operates from 1.7V to 5.25V input and delivers stable power to RF supply rails in space-constrained portable devices.

For engineers reviewing the AP7315D-18FS4-7B datasheet, AP7315D-18FS4-7B pinout, AP7315D-18FS4-7B application, or AP7315D-18FS4-7B equivalent, this LDO is selected for ultra-low-noise biasing of RF transceivers, camera sensor analog blocks, and low-power microcontroller core supplies where fast load transient response and shutdown discharge are critical.

Technical Context

The AP7315D-18FS4-7B implements a CMOS-based LDO architecture with internal voltage reference, error amplifier, current-limit circuit, and active NMOS pass transistor. Its enable-controlled operation supports precise power sequencing in multi-rail systems.

Unlike standard AP7315 variants, the "D" suffix denotes integrated auto-discharge functionality: when EN is pulled low, an internal 30Ω NMOS switch connects VOUT to GND, actively discharging output capacitance to prevent residual voltage hold-up-critical for safe system reset and I/O isolation.

Key Specifications

Pinout & Package

AP7315D-18FS4-7B is housed in a 1.0mm × 1.0mm, 0.4mm pitch X2-DFN1010-4 package with wettable flank leads and thermal pad. The package enables high-density PCB layouts and efficient thermal dissipation via exposed pad soldered to GND plane.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1700T-1802E/TT and XC6210B182MR-G, AP7315D-18FS4-7B uniquely balances low noise (60µV_rms), high PSRR (75dB), and integrated discharge (30Ω) - making it optimal for RF and imaging subsystems requiring both cleanliness and deterministic power-down behavior.

Availability

AP7315D-18FS4-7B is available at Aetrix Electronics and suitable for RF power amplifier biasing, CMOS image sensor core supplies, Bluetooth LE SoC core rails, and wearable MCU real-time clock supplies requiring stable component supply, consistent parametric performance, and long-term production continuity.

Supply support for AP7315D-18FS4-7B 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 ICs for power management, signal integrity, and connectivity applications.

The AP7315 series belongs to Diodes' high-performance LDO portfolio, designed specifically for noise-sensitive portable electronics requiring ultra-low noise, high PSRR, and compact packaging in consumer, computing, and wireless infrastructure markets.

FAQ

What is the purpose of the thermal pad on the AP7315D-18FS4-7B package?

The thermal pad is an exposed copper area on the bottom of the X2-DFN1010-4 package, not electrically connected. It must be soldered to a large GND copper pour to enhance heat dissipation-critical for maintaining junction temperature below 125°C at 150mA output under worst-case ambient conditions. It should never be used as a functional GND electrode.

Does AP7315D-18FS4-7B require external capacitors, and what values are recommended?

Yes: a minimum 0.47µF ceramic capacitor is required between VIN and GND, and another 0.47µF ceramic capacitor between VOUT and GND. Both must be placed within 2mm of their respective pins. For high-transient loads, add a 10µF low-ESR tantalum or polymer capacitor in parallel with the VOUT ceramic cap to improve dynamic response.

How does the auto-discharge feature operate, and when is it active?

The auto-discharge FET activates only when the EN pin is driven below 0.5V (logic low), connecting VOUT to GND through a 30Ω channel. It remains inactive during normal operation (EN ≥ 1.3V) and does not affect regulation. Discharge time depends on C_OUT; e.g., 10µF discharges to <0.1V in ~300µs.

Can AP7315D-18FS4-7B be used with input voltages below 1.8V?

No. Although the absolute minimum input is 1.7V, the device cannot regulate 1.8V output with VIN < 2.08V due to its 280mV typical dropout at 150mA. For reliable 1.8V regulation, VIN must be ≥ 2.08V (1.8V + 280mV); operation below this causes output droop and loss of regulation.