Features

• High Voltage Buck Regulator:
  4V to 35V Operating Range
  1.3A Output Current
• OVLO Protects Input to 55V
• Low Voltage Synchronous Buck Regulator:
  2.5V to 5.5V Input Voltage Range
  1.1A Output Current
• Synchronizable, Adjustable 350kHz to 2.5MHz Switching Frequency
• Programmable Power-On Reset Timer
• Programmable Window Mode Watchdog Timer
• Typical Quiescent Current: 290μA
• Short-Circuit Robust
• Programmable Soft-Start
• Low Shutdown Current: I_Q < 1μA
• Available in Thermally Enhanced 28-Lead
  (4mm × 5mm) QFN and 28-Lead TSSOP Packages

Typical Application

Description

The LT3640 is a dual channel, current mode monolithic buck switching regulator with a power-on reset and a watchdog timer. Both regulators are synchronized to a single oscillator with an adjustable frequency (350kHz to 2.5MHz). At light loads, both regulators operate in low ripple Burst Mode® to maintain high efficiency and low output ripple.

The high voltage channel is a nonsynchronous buck with an internal 2.4A top switch that operates from an input of 4V to 35V; a 36.5V OVLO protects the device to 55V. The low voltage channel operates from an input of 2.5V to 5.5V. Internal synchronous power switches provide high efficiency without the need of external Schottky diode. Both channels have cycle-by-cycle current limit, providing protection against shorted outputs.

The power-on reset and watchdog timeout periods are both adjustable using external capacitors. The window mode watchdog timer flags when the μP pulses group too close together or too far apart.

The LT3640 is available in a 28-pin 4mm × 5mm QFN package and 28-pin TSSOP package. Both packages have an exposed pad for low thermal resistance.