The LTC3809 is a synchronous step-down switching regulator controller that drives external complementary power MOSFETs using few external components. It features selectable spread spectrum frequency modulation for low noise operation, constant frequency current mode operation for excellent line and load transient response, and true PLL for frequency locking or adjustment. It has a wide input voltage range and output voltage range, and is suitable for one or two lithium-ion powered devices, portable instruments, and distributed DC power systems.
The LTC3809 is a synchronous step‑down switching regulator controller that drives external complementary MOSFETs with minimal external components. It features a constant‑frequency current‑mode architecture, internal soft‑start, and optional spread‑spectrum modulation for low‑noise operation. The device supports a wide input voltage range and can be synchronized to an external clock between 250 kHz and 750 kHz.
The datasheet provides detailed pin descriptions, electrical characteristics, typical performance graphs, and PCB layout recommendations. It also explains the operation modes (Burst, Pulse‑Skipping, Forced Continuous) and protection features such as over‑voltage, short‑circuit, and undervoltage lockout.
| Input voltage range | 2.75 V – 9.8 V |
|---|---|
| Output voltage range | 0.6 V – VIN |
| Reference voltage | 0.6 V ±1.5 % |
| Switching frequency range | 250 kHz – 750 kHz |
| Quiescent current (normal operation) | 350 µA – 500 µA |
| Sleep mode current | 105 µA – 150 µA |
The LTC3809 operates with an input voltage from 2.75 V up to 9.8 V.
Burst Mode is selected by tying the SYNC/MODE pin to V IN.
The controller can be programmed for frequencies between 250 kHz and 750 kHz.
Normal‑operation quiescent current is between 350 µA and 500 µA.