Texas Instruments LM2940-50CKCSE3

Overview

LM2940-50CKCSE3 from Texas Instruments is a 5 V, 1 A low-dropout linear voltage regulator in TO-220 package, featuring 0.385 V typical dropout at 1 A, reverse-battery protection, and internal short-circuit/thermal protection. It delivers stable output for automotive power rails, engine control units, and industrial sensors where input voltage may dip near regulation threshold.

For engineers reviewing the LM2940-50CKCSE3 datasheet, LM2940-50CKCSE3 pinout, LM2940-50CKCSE3 application, or LM2940-50CKCSE3 equivalent, key selection criteria include dropout voltage under load, quiescent current behavior above 3 V VIN–VOUT differential, thermal resistance (24.8°C/W for KCS), reverse-polarity transient tolerance (–50 V, 100 ms), and output capacitor ESR stability requirements (22 µF minimum, 0.01–1 Ω range).

Technical Context

The LM2940-50CKCSE3 uses a PNP pass transistor architecture enabling ultra-low dropout while maintaining stability with 22 µF output capacitance and controlled ESR. Its quiescent current reduction circuit actively lowers ground current to 30 mA at 5 V differential, rising only during dropout (VIN – VOUT ≤ 3 V).

Designed explicitly for vehicular environments, it integrates mirror-image insertion protection, load-dump shutdown (input transients >45 V), and reverse-battery survival up to –50 V for 100 ms - all without external components. Thermal shutdown and foldback current limiting operate independently of input polarity.

Key Specifications

Pinout & Package

LM2940-50CKCSE3 is housed in a 3-pin TO-220 (KCS) package with tab connected to GND for thermal and electrical grounding. The case serves as the primary heat path; mounting to a heatsink is required for >2.5 W continuous dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2940-50CKCSE3, LM2940-50CKCS offers identical performance with less-defined finish compliance, while TLV1117-50CDCYR trades automotive ruggedness for smaller footprint and lower cost - making LM2940-50CKCSE3 the sole choice for AEC-Q100-aligned power domains requiring reverse-voltage survival and load-dump immunity.

Availability

LM2940-50CKCSE3 is available at Aetrix Electronics and suitable for automotive engine control units, telematics gateways, and industrial sensor nodes requiring stable component supply with guaranteed long-term manufacturability and RoHS-compliant CuSn finish.

Supply support for LM2940-50CKCSE3 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and high-reliability power management solutions, with decades of automotive qualification expertise.

The LM2940 product line was engineered specifically for harsh-automotive environments, delivering integrated reverse-battery, load-dump, and mirror-image protection without external components - targeting ECU, body control, and telematics power rails.

FAQ

What is the maximum input voltage the LM2940-50CKCSE3 can handle continuously?

The LM2940-50CKCSE3 supports a continuous input voltage range of 6.25 V to 26 V. Its absolute maximum rating is 45 V, but operation above 26 V is not recommended for sustained use. During transients like load dump, it automatically shuts down for protection - surviving up to 60 V for ≤1 ms per the datasheet's maximum line transient specification. Always maintain input filtering to limit dV/dt stress on the device.

Does the LM2940-50CKCSE3 require an input capacitor?

The LM2940-50CKCSE3 does not mandate an input capacitor for basic stability, but TI strongly recommends a 0.47 µF ceramic capacitor placed close to the IN pin to suppress high-frequency noise and improve transient response. This capacitor is especially critical when the regulator is located far from the main power supply filter. Without it, the device remains functional but may exhibit increased susceptibility to line noise coupling.

Can the LM2940-50CKCSE3 be used without a heatsink?

LM2940-50CKCSE3 can operate without an external heatsink only if power dissipation stays below ~2.5 W at 75°C ambient - calculated as PD = (VIN – 5 V) × IOUT. At 1 A and VIN = 12 V, PD = 7 W, exceeding the TO-220 package's 24.8°C/W θJA limit. For reliable operation above 2 W, a heatsink or large copper pour (≥2 in²) is required to keep junction temperature ≤125°C.

What output capacitor specifications are mandatory for stable operation of the LM2940-50CKCSE3?

The LM2940-50CKCSE3 requires a minimum 22 µF output capacitor with ESR between 0.01 Ω and 1 Ω across the full operating temperature range. Aluminum electrolytics often fail at low temperatures due to ESR rise; solid tantalum or polymer capacitors are preferred. TI validates stability only with these ESR bounds - violating them risks oscillation, even if capacitance is higher.

Is the LM2940-50CKCSE3 pin-compatible with other TO-220 LDOs like the 7805?

No, the LM2940-50CKCSE3 is not pin-compatible with standard 78xx regulators. Its pinout is IN–GND–OUT (pin 1–2–3), whereas 7805 uses IN–GND–OUT in the same order but lacks reverse-polarity protection, has higher dropout (~2 V), and no quiescent current reduction. Swapping them requires verifying layout clearance for GND-tab thermal connection and validating transient immunity - direct replacement is unsafe.