| Pin # | Name | Function | Connection in Schematic | | :--- | :--- | :--- | :--- | | 1 | VIN | Main power input (3.3V-5V) | Connect to 5V USB or battery (+) via 10µF ceramic cap. | | 2 | EN | Global enable (active high) | Pull to VIN for always-on; or connect to MCU GPIO. | | 3 | SW | Switching node (Buck converter) | Connect to power inductor (2.2µH to 4.7µH). | | 4 | BST | Bootstrap capacitor pin | Connect 100nF cap between BST and SW. | | 5 | FB | Feedback for buck output | Connect voltage divider to set Vout (e.g., 3.3V). | | 6 | COMP | Compensation pin | RC network to ground (stability). | | 7 | AGND | Analog ground | Connect to main ground plane (star point). | | 8 | PGND | Power ground | Wide trace to input capacitor ground. | | 9 | LDO_IN | Input for LDOs | Usually tied to buck output (3.3V) or separate VIN. | | 10 | LDO1_OUT | Output LDO1 (e.g., 1.8V) | 2.2µF ceramic cap to ground. | | 11 | LDO2_OUT | Output LDO2 (e.g., 1.2V) | 1µF ceramic cap to ground. | | 12 | LDO_EN | LDO enable | If separate from main EN, tie to VIN. | | 13-16 | NC | No connect | Leave floating. |
Download a generic buck converter calculator to fine-tune your feedback resistors, or use an oscilloscope to verify the SW node waveform (should be a clean 1.5MHz square wave). Have a correction or an original Lac503P datasheet? Share it in the comments below. Our community of hardware engineers is actively working to document this obscure but essential PMIC. lac503p schematic
Meta Description: Need the lac503p schematic ? This article provides a detailed breakdown of the Lac503P power management IC, including pin configuration, internal block diagram, typical application circuit, and troubleshooting tips for engineers and hobbyists. Introduction: What is the Lac503P? The Lac503P is a widely used, highly integrated Power Management Integrated Circuit (PMIC), commonly found in portable consumer electronics, single-board computers, and battery-operated devices. While the exact manufacturer specifications can vary (with "Lac" often being a shorthand or rebranding for specific OEM batches), the core topology of the IC revolves around a high-efficiency step-down (buck) converter combined with low-dropout (LDO) regulators. | Pin # | Name | Function |
LDO_IN(Pin9)---------+----> From VOUT (3.3V) | LDO1_OUT(Pin10)------+---- C5 ---> 1.8V out LDO2_OUT(Pin11)------+---- C6 ---> 1.2V out | | 4 | BST | Bootstrap capacitor
For repair technicians and hardware designers, finding a clear is critical. Without it, diagnosing a dead device, reverse-engineering a board, or building a custom power supply becomes a guessing game. This article reconstructs the standard application circuit based on common PMIC architectures and available datasheet fragments.