42V, 3A Synchronous Step-Down Regulator with 2.5µA Quiescent Current

The LT8609/LT8609A/LT8609B is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 1.7µA of nonswitching quiescent current. The LT8609/LT8609A/LT8609B can deliver 3A of continuous current. Burst Mode operation enables high efficiency down to very low output currents while keeping the output ripple below 10mVP-P. A SYNC pin allows synchronization to an external clock, or spread spectrum modulation for low EMI operation. Internal compensation with peak current mode topology allows the use of small inductors and results in fast transient response and good loop stability. The EN/UV pin has an accurate 1V threshold and can be used to program VIN UVLO or to shut down the part. A capacitor on the TR/SS pin programs the output voltage ramp rate during start-up while the PG flag signals when VOUT is within ±8.5% on the adjustable output parts or ±7.5% on the fixed output parts of the programmed output voltage as well as fault conditions. The LT8609A has slower switch edges for lower EMI emissions. The LT8609B operates in pulse-skipping mode only.

Pulse-Skipping Mode, Burst Mode Operation

Switch Edge Speed

LT8609

Both

Fast

LT8609A

Both

Medium

LT8609B

Pulse-Skipping

Fast

Applications

* GSM Transceivers

* General Purpose Step-Down

* Low EMI Step-Down

* Wide Input Voltage Range: 3.0V to 42V

* Ultralow Quiescent Current Burst Mode® Operation:

* <2.5µA IQ Regulating 12VIN to 3.3VOUT

* Output Ripple <10mVP-P

* High Efficiency 2MHz Synchronous Operation:

* >93% Efficiency at 1A, 5VOUT from 12VIN

* 3A Maximum Continuous Output

* Fast Minimum Switch-On Time: 45ns

* LT8609A Available in Fixed 3.3V and 5V Output

* Adjustable and Synchronizable: 200kHz to 2.2MHz