Diodes Incorporated AP3591FNTR-G1

Overview

AP3591FNTR-G1 from Diodes Incorporated is a single-phase synchronous buck controller implementing adaptive constant-on-time (COT) PWM control for notebook and low-voltage distributed power applications. It delivers 0.75V–5.5V output with ±1% feedback reference accuracy (0.742–0.758V), supports 4.5V–26V input, and features integrated DEM/CCM mode selection via EN/DEM pin voltage, internal soft-start (1.2ms typical), and power-good monitoring with ±5% threshold hysteresis.

For engineers reviewing the AP3591FNTR-G1 datasheet, AP3591FNTR-G1 pinout, AP3591FNTR-G1 application, or AP3591FNTR-G1 equivalent, key selection criteria include its resistor-programmable switching frequency (100–700kHz), R_DS(ON)-based current sensing with 4500ppm/°C temperature compensation, integrated bootstrap diode, safe pre-biased start-up, and dual over-current protection (positive/negative) with programmable trip point.

Technical Context

The AP3591FNTR-G1 uses adaptive COT control without an external clock, deriving on-time from V_OUT/V_IN ratio and R_TON, enabling stable operation across wide input-output voltage ratios. Its error amplifier compares FB to a 0.75V reference, and internal soft-start ramps V_SS to 95% of reference in 1.2ms to limit inrush current.

Mode selection is voltage-defined: EN/DEM ≥2.9V enables Diode Emulation Mode (light-load efficiency), floating EN/DEM forces Continuous Conduction Mode (constant-frequency noise control), and EN/DEM ≤1.6V disables operation. Protection includes UVLO (3.9V V_DD threshold), OTP (160°C shutdown), OVP/UVP (125%/70% V_FB thresholds), and cycle-by-cycle NOCP with 400ns recovery delay.

Key Specifications

Pinout & Package

AP3591FNTR-G1 is housed in a thermally enhanced U-QFN3535-14 package (3.5mm × 3.5mm, 0.5mm pitch) with exposed thermal pad soldered to PCB ground for optimal power dissipation (θ_JA = 60°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck controller applications.

Compared with RT8205AZSP and ISL95836IRZ, the AP3591FNTR-G1 uniquely combines adaptive COT control, DEM/CCM mode flexibility, integrated soft-stop, and pre-biased start-up in a 3.5×3.5mm package-making it optimal for space-constrained, battery-aware single-phase applications where transient response and startup safety are critical.

Availability

AP3591FNTR-G1 is available at Aetrix Electronics and suitable for notebook computer power rails, AIO PC core voltage regulation, and low-voltage distributed power systems requiring stable component supply despite its obsolete status through legacy channel sourcing.

Supply support for AP3591FNTR-G1 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 integrated circuits, specializing in high-performance power management, signal integrity, and protection solutions for computing, industrial, and consumer markets.

The AP3591 product line delivers synchronous buck controllers optimized for high-efficiency, low-noise, and robust transient performance in portable computing and compact embedded power systems.

FAQ

What is the recommended minimum output capacitance for stable AP3591FNTR-G1 operation?

The AP3591FNTR-G1 does not require minimum ESR for stability due to its adaptive COT architecture. Minimum capacitance is determined by ripple and transient requirements: 10µF ceramic (e.g., Murata GRM31CR61E106KA12) is specified in the typical application circuit for 1.05V/10A operation, with bulk capacitance (e.g., 220µF Sanyo 6SVPE220M) added for hold-up time.

How does the AP3591FNTR-G1 handle startup into a pre-biased output voltage?

During pre-biased startup, the AP3591FNTR-G1 monitors V_OUT via the VOUT pin and inhibits both UGATE and LGATE until the internal soft-start ramp exceeds the sensed output voltage. This prevents reverse current flow through the low-side MOSFET body diode and ensures monotonic, glitch-free ramp-up from any initial V_OUT level.

Can the AP3591FNTR-G1 operate with only the VDD supply, or is VDDP required?

VDDP is mandatory: it supplies the high- and low-side gate drivers. The datasheet specifies VDDP = 4.5–5.5V, identical to VDD. Both must be present and bypassed with 1µF ceramic capacitors to PGND (VDDP) and GND (VDD). Omitting VDDP disables UGATE and LGATE outputs, halting converter operation.

What is the maximum allowable voltage on the PHASE pin relative to GND?

The absolute maximum rating for V_PHASE (voltage from PHASE to GND) is −0.3V to +36V. This accommodates typical buck topologies where PHASE swings from near-GND (during LGATE conduction) to up to VIN + boot voltage (during UGATE conduction), supporting 26V input with margin for ringing and overshoot.