Microchip Technology LR645N3-G-P003

Overview

LR645N3-G-P003 from Microchip Technology is a high-input voltage, fixed-output linear regulator in TO-92 package, delivering 10V ±0.7V output at up to 3.0mA continuous current with 50µA typical quiescent supply current and 15–450V input range. It serves as an off-line SMPS startup supply, eliminating high-wattage start-up resistors in AC/DC power converters.

For engineers reviewing the LR645N3-G-P003 datasheet, LR645N3-G-P003 pinout, LR645N3-G-P003 application, or LR645N3-G-P003 equivalent, key selection criteria include its 450V absolute maximum input rating, -55°C to +150°C operating temperature range, 0.1µA off-state leakage, 50dB minimum ripple rejection, and fixed 10V output without external trim components.

Technical Context

The LR645N3-G-P003 implements a monolithic high-voltage linear regulation architecture with internal pass transistor and bandgap reference, enabling direct connection to rectified AC mains without external step-down. Its thermal design supports 0.74W dissipation at 25°C ambient in TO-92, with derating per θ_JA = 132°C/W.

It operates exclusively in fixed-output mode (no TRIM or GATE pins), requiring no external feedback network. Input-to-output differential voltage directly determines power dissipation-e.g., 400V_IN–10V_OUT at 3mA yields 1.23W-making thermal management critical in sustained-load applications.

Key Specifications

Pinout & Package

LR645N3-G-P003 uses a 3-lead TO-92 package (Microchip package code N3) with leads arranged in straight-line configuration: Pin 1 = VIN, Pin 2 = GND, Pin 3 = VOUT. The package is Pb-free/ROHS-compliant (G suffix) and supplied in 2000/reel (P003).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LR645N3-G-P003, LR645N5-G offers superior thermal performance in high-ambient environments while maintaining identical regulation behavior, whereas LR645N8-G provides SMT manufacturability at slightly reduced thermal margin-both retain the same 10V fixed output, 450V max input, and 3mA load capability.

Availability

LR645N3-G-P003 is available at Aetrix Electronics and suitable for off-line SMPS startup circuits, low-power AC/DC regulators, and noisy-input industrial controls requiring stable component supply with lead-free compliance and reel packaging.

Supply support for LR645N3-G-P003 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

Microchip Technology is a U.S.-based semiconductor manufacturer specializing in microcontrollers, analog devices, and power management ICs, with ISO/TS-16949 certified wafer fabrication and assembly facilities.

The LR645 product line delivers high-input voltage linear regulation for switch-mode power supply startup and auxiliary power generation, targeting cost-sensitive, space-constrained AC/DC systems where galvanic isolation is handled externally.

FAQ

What is the maximum input voltage rating for LR645N3-G-P003?

The LR645N3-G-P003 has an absolute maximum input voltage rating of 450V DC, verified per Microchip DS20005384A-page 3. This allows direct connection to rectified 277VAC mains (≈390V peak) with 60V design margin. Operation above 450V risks permanent damage; transient spikes must be clamped externally using TVS diodes rated ≤450V.

Does LR645N3-G-P003 provide galvanic isolation between input and output?

No, LR645N3-G-P003 does not provide galvanic isolation. As explicitly stated in the datasheet warning on page 2, lethal voltages may appear on all pins when operated from AC line. System-level isolation must be implemented externally via transformer-based topologies or optocoupled feedback - the LR645N3-G-P003 itself is a single-die linear regulator with common GND reference.

Can LR645N3-G-P003 be used for continuous 3mA load applications?

Yes, LR645N3-G-P003 is rated for 3.0mA continuous output current at 10V, but power dissipation must be validated. At 400V_IN, dissipation reaches 1.23W (calculated per page 6), exceeding the TO-92 package's 0.74W limit at 25°C. For continuous 3mA use, input voltage must be limited to ≤270V or ambient temperature reduced; otherwise, thermal shutdown or reliability degradation will occur.

What output capacitor value is required for stable operation of LR645N3-G-P003?

LR645N3-G-P003 requires a minimum output capacitance of 0.01µF (10nF) ceramic capacitor for stability, as specified in Section 3.1 and Figure 3-1. Larger values (e.g., 1µF X7R) improve transient response and ripple suppression but are not mandatory. Electrolytic capacitors are discouraged due to ESR-related instability risks noted in the functional description.

Is LR645N3-G-P003 compatible with external MOSFETs for higher output current?

No, LR645N3-G-P003 is the fixed-output 3-terminal version and lacks TRIM and GATE pins required to drive external depletion-mode MOSFETs. Only the 8-lead SOIC variant (e.g., LR645LG-G) supports external FET augmentation up to 150mA. Attempting to connect an external FET to LR645N3-G-P003 will not function and may damage the device due to missing control circuitry.