onsemi FAN1582D12X

Overview

FAN1582D12X from Fairchild Semiconductor is a 3A ultra-low dropout linear regulator in TO-252 DPAK package, delivering adjustable output voltage from 1.3V to 5.7V with 0.4V typical dropout at 3A, 0.5% initial accuracy, and remote sense capability for GTL+ bus termination and embedded processor supplies.

For engineers reviewing the FAN1582D12X datasheet, pinout, applications, or equivalent options, key selection criteria include dropout voltage under full load, thermal resistance (Θ_JC = 3°C/W), remote sensing support, control pin voltage requirements (VCNTL ≥ V_OUT + 1.2V), and stability with low-ESR output capacitors.

Technical Context

The FAN1582D12X uses a dual-supply architecture: VIN powers the output transistor while VCNTL supplies control circuitry, enabling optimized efficiency and eliminating supply-sequencing risks. Its internal NPN pass element and 1.25V reference allow precise output regulation via external resistor divider.

True remote sensing via VSense pin compensates for PCB trace IR drop, and on-chip thermal shutdown activates at 150°C. Frequency compensation relies on output capacitance (≥22µF solid tantalum) with ESR < 0.3Ω to ensure stability across load transients.

Key Specifications

Pinout & Package

5-Lead TO-252 DPAK package with exposed thermal pad (tab connected to V_OUT). Mounting requires soldering the tab to ≥0.5 in² copper area for Θ_JA ≤ 40°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with NCP1582DSADJR2G and TPS75733KTTT, the FAN1582D12X uniquely combines adjustable output, remote sensing, and dual-supply control - making it the only viable option for GTL+ V_TT and split-rail embedded processor designs requiring trace-drop compensation and sequencing control.

Availability

FAN1582D12X is available at Aetrix Electronics and suitable for GTL+ bus termination, embedded microprocessor core supplies, and DDR memory termination requiring stable component supply across industrial, computing, and communications platforms.

Supply support for FAN1582D12X 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

Fairchild Semiconductor (now part of ON Semiconductor) is a fabless semiconductor company specializing in power management, analog, and interface ICs for industrial, computing, and consumer applications.

The FAN1582 series was designed specifically for ultra-low-voltage, high-current termination and logic supply applications - addressing GTL+, DDR, and embedded processor requirements where dropout, transient response, and remote sensing are critical.

FAQ

What is the minimum input voltage required for FAN1582D12X to regulate a 1.3V output?

The FAN1582D12X requires V_IN ≥ V_OUT + 0.5V (typical dropout) to maintain regulation. For a 1.3V output, minimum V_IN is 1.8V. However, VCNTL must also be ≥ V_OUT + 1.2V (i.e., ≥2.5V), so the effective system minimum is dictated by the higher of the two supplies. The FAN1582D12X datasheet specifies 1.75V as absolute minimum V_IN, but stable operation at 1.3V output requires ≥1.85V input under full 3A load.

Does FAN1582D12X support remote sensing, and how is it implemented?

Yes, the FAN1582D12X supports true remote sensing via its dedicated VSense pin (Pin 1). To implement, connect VSense directly to the load's V_OUT point - not to the regulator's V_OUT pin - to compensate for voltage drop across PCB traces. This configuration ensures the feedback loop regulates voltage precisely at the load, maintaining accuracy within ±15mV even with 50mΩ trace resistance at 3A. The FAN1582D12X will not function correctly if VSense is left unconnected or tied to V_OUT.

What output capacitor values and types are required for stable operation of FAN1582D12X?

The FAN1582D12X requires a minimum 22µF solid tantalum or 100µF aluminum electrolytic capacitor on V_OUT for stability. Capacitor ESR must be <0.3Ω; ceramic capacitors alone are insufficient due to near-zero ESR. For optimal transient response, add a 1µF ceramic bypass at the ADJ pin. The FAN1582D12X datasheet confirms stability across 1–10A load steps only when using recommended output capacitance and ESR - undersized or high-ESR capacitors risk oscillation or overshoot.

Can FAN1582D12X be used with VCNTL and VIN tied together?

Yes, the FAN1582D12X can operate with VCNTL and VIN shorted, functioning as a single-supply LDO. In this mode, dropout is determined by the minimum VCNTL requirement (≥V_OUT + 1.2V), effectively increasing the minimum input voltage needed. While functional, this configuration forfeits the primary advantage of the dual-supply architecture - independent sequencing and reduced dropout - and is not recommended for GTL+ or DDR termination where VCNTL headroom optimization is critical. The FAN1582D12X datasheet explicitly validates this configuration but notes degraded thermal performance.

What is the thermal shutdown threshold and recovery behavior of FAN1582D12X?

The FAN1582D12X activates thermal shutdown at approximately 150°C junction temperature, halting output current until junction temperature falls by ~15°C (hysteresis). Recovery is automatic and does not require power cycling. During shutdown, the device draws only control-circuit quiescent current (<6mA), preventing thermal runaway. The FAN1582D12X datasheet specifies Θ_JC = 3°C/W, meaning sustained 3A operation at 1.5V output from 3.3V input requires ≥5°C/W total Θ_JA to stay below 150°C ambient - achievable only with adequate copper area and optional heatsink.