LR745N3-G

Power Management - Specialized Overview

The LR745N3-G is a specialized power management IC designed as a high-input voltage start-up circuit for Switch-Mode Power Supplies (SMPS). It operates with an input voltage range of 35 V to 450 V and provides a regulated output voltage between 18 V and 24 V. The device delivers an output current of 3 mA with an input current consumption of 500 uA. It is housed in a TO-92 (SOT-57) through-hole package and functions within a temperature range of -55°C to +125°C.

Power Management - Specialized Feature Summary

• High input voltage tolerance suitable for direct connection to rectified mains or high-voltage DC buses
• Integrated regulation providing stable start-up voltage for downstream PWM controllers
• Low quiescent current operation to minimize standby power loss during initial charging phases

Power Management - Specialized Applications

• Start-up circuits for flyback converters in offline power supplies
• Bias supply generation for high-voltage SMPS topologies
• Gate drive power initialization in industrial motor drives

Power Management - Specialized Procurement Notes

Verify the specific suffix 'N3' confirms the TO-92 package variant, as other suffixes may indicate different packages like SOT-89. Confirm RoHS compliance status directly with Microchip Technology documentation, as historical batches may vary. Ensure the application voltage does not exceed the 450 V maximum rating under all transient conditions.

Power Management - Specialized Selection Notes

Select this component when a simple, cost-effective solution is required to provide a regulated bias voltage from a high-voltage rail. It is appropriate for designs where low start-up current is critical and the load requirements fit within the 3 mA output capability. Consider thermal dissipation if operating near the upper limits of the input voltage range.

Power Management - Specialized Part Context

The LR745 series belongs to Microchip's specialized PMIC portfolio, focusing on high-voltage start-up applications. This family allows designers to replace discrete resistor-capacitor networks with a single integrated regulator, simplifying PCB layout and improving reliability in offline power conversion systems.

Power Management - Specialized Replacement Considerations

Check for LR745N8-G for surface-mount SOT-89 packaging compatibility. Verify functional equivalence with other high-voltage start-up regulators from manufacturers like ON Semiconductor or STMicroelectronics, ensuring pinout and electrical specifications match the existing design constraints.