Designed and validated a 3.3 V precision LDO regulator using a TL431 shunt reference and TIP42C PNP pass transistor. Achieved 3.308 V regulated output with 0.24% output voltage error and accurate 2.495 V reference operation. Completed schematic design, PCB layout, manufacturing documentation generation, and design verification through simulation and hardware implementation.
| Parameter | Target | Simulated |
|---|---|---|
| Vout | 3.3V ±1% | 3.308 V ✓ |
| REF pin voltage | 2.495 V | 2.495 V ✓ |
| PSRR @ 1kHz | >60 dB | TBD |
| Load regulation | <1% | TBD |
| Line regulation | <0.5% | TBD |
| Output noise | <50 µV/√Hz | TBD |
| Dropout voltage | <300 mV | ~690 mV |
- TL431 chosen over Zener: 0.5% accuracy vs ~5% for Zener
- PNP pass transistor (TIP42C): lower cost; PMOS gives better PSRR but requires gate drive — PNP simpler for discrete design
- Cc = 100nF across R1 adds phase-compensating zero, reduces transient overshoot
- Low-ESR Cout (100µF): too low ESR causes oscillation, too high degrades transient response
schematic.pdf— KiCad 10 schematicpcb_layout.pdf— PCB layout (2-layer)LDO.asc— LTspice XVII simulation fileTL431.sub— TL431 behavioral SPICE modelgerbers/— Gerber files for PCB fabricationwaveforms/— Simulation result screenshots3D-renders/— KiCad 3D PCB renders
LTspice XVII · KiCad 10 · TI TL431 SPICE model
- TI TL431 Datasheet (SLVS543)
- TI App Note SLVA756 — LDO Basics
- TIP42C Datasheet — ST Microelectronics