onsemi CS5205A-1GT3

Overview

CS5205A-1GT3 from onsemi is a 5.0 A adjustable linear regulator with ±1% output voltage accuracy, 1.15 V dropout at full load, and thermal/overcurrent/SOA protection. It operates from 1.25 V to 13 V output range using two external resistors and is designed for microprocessor post-regulation and low-voltage, high-transient-response power supplies.

For engineers reviewing the CS5205A-1GT3 datasheet, pinout, applications, or equivalent options, key selection factors include dropout voltage at 5 A, reference voltage stability over temperature, thermal shutdown threshold, SOA-limited current vs. input–output differential, and TO-220-3 package thermal resistance (R_ΘJC = 1.6 °C/W).

Technical Context

The CS5205A-1GT3 uses a composite PNP–NPN pass transistor architecture enabling low dropout and fast transient response. Its internal bandgap reference (1.254 V typical) feeds an error amplifier that controls output via the adjust pin, with 50 µA typical adjust pin current introducing a calculable error term in voltage-setting resistor networks.

Protection is implemented through three independent circuits: thermal shutdown activating at 150 °C (25 °C hysteresis), foldback current limiting (5.5–8.5 A depending on VIN–VOUT), and Safe Operating Area circuitry that dynamically reduces maximum output current as input–output differential increases - preventing device destruction under high-power stress conditions.

Key Specifications

Pinout & Package

The CS5205A-1GT3 is supplied in the TO-220-3 package (Case 221A), with the metal tab electrically connected to VOUT and serving as the primary heat transfer surface. Mounting requires thermal compound and mechanical isolation if VOUT is not ground-referenced.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT1084CT-5#PBF and LM396T/NOPB, the CS5205A-1GT3 offers superior dropout performance and integrated SOA protection in a standard TO-220-3 outline - making it optimal for space-constrained, thermally demanding 5 A applications where input–output differentials vary dynamically.

Availability

CS5205A-1GT3 is available at Aetrix Electronics and suitable for microprocessor core supplies, FPGA I/O regulation, industrial PLC power modules, and precision test equipment reference rails requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for CS5205A-1GT3 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 supplier focused on energy-efficient innovation for automotive, industrial, cloud, and IoT applications.

The CS5205A-1GT3 belongs to onsemi's high-current linear regulator product line, engineered specifically for post-regulation in mixed-signal systems where low noise, fast transient response, and robust fault protection are mandatory.

FAQ

What is the minimum input–output differential voltage required for the CS5205A-1GT3 to maintain regulation at 5.0 A?

The CS5205A-1GT3 requires a minimum input–output differential voltage of 1.15 V at 5.0 A and TJ ≥ 25°C to maintain regulation. This dropout voltage increases slightly with junction temperature and decreases marginally at lower load currents. The datasheet specifies 1.25 V maximum dropout under worst-case conditions, so design margins should assume ≥1.3 V for reliable operation across temperature and tolerance extremes. The CS5205A-1GT3 achieves this with its composite PNP–NPN pass transistor structure.

Can the CS5205A-1GT3 be used without an output capacitor, and what type is recommended?

No, the CS5205A-1GT3 requires an output capacitor for loop stability, start-up behavior, and transient response. A minimum 22 µF tantalum capacitor is specified; aluminum electrolytic is acceptable but exhibits greater ESR variation at low temperature. Ceramic capacitors alone are not recommended due to near-zero ESR causing potential instability. For best results in microprocessor applications, use a parallel network of tantalum and ceramic capacitors placed close to the load. The CS5205A-1GT3's stability is explicitly characterized with these types.

How does the Safe Operating Area (SOA) protection function in the CS5205A-1GT3?

The CS5205A-1GT3's SOA protection dynamically limits output current based on the instantaneous VIN–VOUT differential voltage - reducing maximum allowable current as the differential increases to prevent second breakdown in the pass transistor. Unlike fixed current limiting, this circuit adapts to operating conditions, allowing higher current at low differentials (e.g., 5 A at 1.2 V) and progressively restricting current at higher differentials (e.g., ~2 A at 6 V). This behavior is inherent to the CS5205A-1GT3's internal protection architecture and requires no external components.

Is the CS5205A-1GT3 pin-compatible with other regulators, and what are the implications?

Yes, the CS5205A-1GT3 is pin-compatible with the LT1084 family in TO-220-3 and D2PAK-3 packages. This allows direct PCB replacement where layout supports the same footprint. However, the CS5205A-1GT3 delivers 1.15 V dropout versus ~1.3 V for LT1084, improving efficiency, and includes SOA protection not present in LT1084. No changes to external components are needed, but designers should verify thermal performance given the tighter dropout margin. The CS5205A-1GT3 maintains identical pin 1 (Adj), pin 2 (VOUT), pin 3 (VIN) assignment.

What is the role of the adjust pin current in output voltage accuracy of the CS5205A-1GT3?

The CS5205A-1GT3's adjust pin draws 50 µA typical (up to 100 µA) current, which flows through the lower resistor (R2) in the voltage-setting divider and introduces an error term: V_OUT = V_REF(1 + R1/R2) + I_ADJ×R2. For 1% output accuracy, this error must be ≤12.5 mV at 1.25 V reference. Using R2 ≤ 250 Ω keeps I_ADJ×R2 ≤ 25 mV - but precision designs require trimming R1 or selecting R2 to cancel the effect. This behavior is explicitly modeled in the CS5205A-1GT3's application equations.