Diodes Incorporated AP3585BMPTR-G1

Overview

AP3585BMPTR-G1 from Diodes Incorporated is a single-phase synchronous buck PWM controller in SO-8EP package, designed for 4.5V–13.2V input and 0.6V output (±1.5% reference accuracy), operating at fixed 300kHz frequency with integrated 12V bootstrap drivers and built-in boot diode. It delivers fast transient response via 10MHz GBW error amplifier and supports lossless over-current protection using low-side MOSFET R_DS(ON). Used in DDR/SDRAM bus termination and graphics card subsystem supplies.

For engineers reviewing the AP3585BMPTR-G1 datasheet, AP3585BMPTR-G1 pinout, AP3585BMPTR-G1 application, or AP3585BMPTR-G1 equivalent, key selection criteria include its 0.6V internal reference, 300kHz fixed-frequency operation, SO-8EP thermal performance (θ_JA = 70°C/W), voltage-mode control architecture, and programmable OCP via LGATE/OCSET pin.

Technical Context

This controller implements voltage-mode PWM control with a single feedback loop, using an internal 0.6V reference and COMP/EN pin for both loop compensation and enable/disable functionality. Its adaptive shoot-through protection monitors UGATE and PHASE to prevent cross-conduction during high-side and low-side MOSFET switching transitions.

The error amplifier provides 10MHz gain-bandwidth and 6V/µs slew rate, enabling high-loop bandwidth for sub-100µs load transient recovery. Over-current protection is implemented via current-sensing across the low-side MOSFET's R_DS(ON), with threshold set by external resistor on LGATE/OCSET pin and internal 10µA current source.

Key Specifications

Pinout & Package

AP3585BMPTR-G1 is housed in a thermally enhanced SO-8EP (exposed pad) package, with the exposed pad soldered directly to PCB ground plane for optimal thermal dissipation (θ_JA = 70°C/W, θ_JC = 22°C/W). The 8-pin layout supports compact 2-layer board designs with minimal external components.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2307DN-LF-Z and TPS54331DR, AP3585BMPTR-G1 offers superior thermal performance in SO-8EP, built-in boot diode for simplified layout, and dedicated 0.6V reference optimized for DDR VTT - making it the most direct fit for memory subsystems requiring precision, reliability, and minimal BOM.

Availability

AP3585BMPTR-G1 is available at Aetrix Electronics and suitable for DDR3/DDR4 bus termination, graphics card subsystems, and industrial FPGA core supplies requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.

Supply support for AP3585BMPTR-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 analog ICs, specializing in high-efficiency power management, signal integrity, and protection solutions for computing, industrial, and consumer markets.

The AP3585 series belongs to Diodes' synchronous buck controller product line, engineered specifically for high-density, cost-sensitive subsystem power supplies in memory interfaces and graphics platforms where precision regulation and thermal robustness are critical.

FAQ

What is the purpose of the LGATE/OCSET pin on AP3585BMPTR-G1?

The LGATE/OCSET pin serves dual functions: it drives the low-side MOSFET gate and sets the over-current protection threshold. An external resistor from this pin to GND, combined with the internal 10µA current source, determines the OCP trip point using V_OCSET = I_OCSET × R_OCSET. This enables lossless current sensing without a dedicated sense resistor, preserving efficiency and reducing thermal stress.

Does AP3585BMPTR-G1 support start-up into a pre-biased output?

Yes, AP3585BMPTR-G1 supports start-up into a pre-biased output. During soft-start initiation, the controller monitors the FB pin voltage and disables UGATE/LGATE switching if the output voltage exceeds the internal reference before regulation begins. This prevents reverse current flow and ensures safe ramp-up even when downstream circuitry holds residual voltage on the output rail.

How does the built-in bootstrap diode improve design simplicity?

The integrated bootstrap diode eliminates the need for an external Schottky diode between BOOT and PHASE pins. This reduces component count by one, saves PCB area, removes a potential failure point, and ensures consistent boot capacitor charging behavior across temperature and process variations - simplifying layout and improving long-term reliability in high-volume manufacturing.

What thermal advantages does the SO-8EP package provide over standard SO-8?

The SO-8EP package features an exposed thermal pad that must be soldered to a large PCB ground plane, reducing junction-to-ambient thermal resistance to 70°C/W (vs. 115°C/W for standard SO-8). This 39% improvement allows sustained operation at higher ambient temperatures or higher output currents without thermal derating - critical for dense graphics or server board layouts where airflow is limited.