onsemi CS5257A-1GDP5

Overview

CS5257A-1GDP5 from onsemi is a 7.0 A adjustable low-dropout linear regulator with dual-supply architecture (VPOWER and VCONTROL), remote voltage sensing (VSENSE), and 1.25 V to 5.0 V output programmability. It delivers <0.35 V dropout at 7.0 A load, features 1.5% trimmed reference, and is optimized for high-current motherboard secondary supplies-e.g., generating stable 2.5 V @ 7.0 A for advanced microprocessors.

For engineers reviewing the CS5257A-1GDP5 datasheet, pinout, applications, or equivalent options, key selection criteria include verified VPOWER/VCONTROL dropout behavior, Kelvin-sense implementation requirements, thermal shutdown hysteresis (25°C), and compatibility with high-transient-load systems requiring <1.0 mV load regulation at the sense point.

Technical Context

The CS5257A-1GDP5 employs a PNP–NPN pass transistor pair with physically separated VPOWER (collector) and VCONTROL (base drive) inputs to minimize power dissipation and enable ultra-low dropout. Its error amplifier uses a dedicated VSENSE pin for true Kelvin feedback, decoupling regulation accuracy from PCB trace resistance.

Control loop stability relies on external capacitor networks: a 0.1 µF bypass on the Adjust pin improves transient response, while ≥300 µF output capacitance (tantalum/aluminum electrolytic) ensures loop stability and load-step performance. Internal protection includes current limiting (7.1–10 A), short-circuit foldback (~5–9 A), and thermal shutdown activation at ~150°C with 25°C hysteresis.

Key Specifications

Pinout & Package

CS5257A-1GDP5 is supplied in the D2PAK-5 surface-mount package (Case 936AC), with exposed tab electrically connected to VOUT for thermal and electrical integration. The package supports high-current PCB layouts with low-inductance power paths and direct heatsink mounting.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable high-current LDO applications.

Compared with LT1580CS8#PBF and TPS75733KTTT, the CS5257A-1GDP5 uniquely combines 7.0 A output, dedicated VSENSE, and dual-supply architecture-enabling both ultra-low dropout and millivolt-level regulation accuracy at the load, which neither alternative achieves simultaneously.

Availability

CS5257A-1GDP5 is available at Aetrix Electronics and suitable for high-current motherboard power delivery, industrial PLC I/O conditioning, and FPGA auxiliary rail generation requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for CS5257A-1GDP5 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

onsemi (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in energy-efficient power management, analog, and sensor solutions for automotive, industrial, and cloud infrastructure markets.

The CS5257A-1GDP5 belongs to onsemi's high-current linear regulator product line, engineered specifically for next-generation microprocessor secondary power rails where remote sensing, fast transient response, and thermal robustness are mandatory.

FAQ

What is the maximum allowable voltage difference between VPOWER and VOUT for the CS5257A-1GDP5?

The absolute maximum VPOWER − VOUT differential is 6.0 V per datasheet specifications. Exceeding this risks destruction of the pass transistor during short-circuit events before protection circuits activate. For fail-safe operation above 6.0 V differential, external clamp circuitry-as shown in Figure 17 of the CS5257A-1 datasheet-is required. The CS5257A-1GDP5 itself does not include internal overvoltage clamping beyond this limit.

Can the CS5257A-1GDP5 operate with only VCONTROL connected and VPOWER disconnected?

Yes-the CS5257A-1GDP5 can source up to 50 mA through VCONTROL alone when VPOWER is unconnected, as confirmed in Electrical Characteristics (page 3). However, this mode delivers negligible output current and is intended only for bias verification or functional testing-not operational use. Full 7.0 A output requires both VCONTROL and VPOWER supplies active and within specified voltage ranges.

How does the Adjust pin current affect output voltage accuracy in the CS5257A-1GDP5?

The Adjust pin draws ~50 µA (typical), which flows through the lower resistor (R2) of the output divider and introduces an offset error: VOUT = 1.253 V × (1 + R1/R2) + (IADJ × R2). For 1% output accuracy, R2 should be ≤1 kΩ; higher values increase error. The CS5257A-1GDP5 datasheet provides curves (Figures 9–11) showing IADJ variation vs. temperature and supply differentials to aid precision design.

Is thermal compound required when mounting the CS5257A-1GDP5 to a heatsink?

Yes-thermal compound is mandatory for reliable thermal performance. The D2PAK-5 package has RJC = 1.4°C/W, but effective heat transfer depends on interfacial contact quality. Without thermal grease or phase-change material, air gaps cause significant thermal resistance increase, risking junction temperatures exceeding 150°C even below rated load. onsemi explicitly states "thermal compound is necessary" in the CS5257A-1 datasheet (page 9).

Does the CS5257A-1GDP5 support power supply sequencing, and what happens if VPOWER rises before VCONTROL?

The CS5257A-1GDP5 incorporates intrinsic sequencing logic: if VPOWER rises before VCONTROL, the output remains fully off-no current flows. If VCONTROL rises first, output current is limited to ~3 mA until VPOWER reaches regulation threshold. This prevents unregulated turn-on and ensures safe startup. These behaviors are documented in the "Theory of Operation" section (page 6) of the CS5257A-1 datasheet.