Features

• Wide Input Range:
  Operation from 3.8V to 36V
• Low Ripple (<25mV_P-P ) Burst Mode Operation:
  I_Q = 115μA at 12V_IN to 3.3V and 5V
• Programmable, Defeatable Window Watchdog Timer
• Two Independently Programmable Power-On-Reset Timers
• Synchronizable, Adjustable 350kHz-2.2MHz Switching Frequency
• Two 800mA Output Switching Regulators with Internal Power Switches
• Programmable Input Undervoltage Lockout with Hysteresis
• Thermally Enhanced 24-Pin TSSOP and 4mm × 4mm QFN Packages

Typical Application

Description

The LT3688 is an adjustable frequency (350kHz to 2.2MHz) dual monolithic step-down switching regulator with two power-on reset timers and a watchdog timer. The regulator operates off inputs up to 36V. Low ripple Burst Mode® operation maintains high efficiency at low output current while keeping output ripple below 25mV in a typical application, with input quiescent current of just 115μA. Shutdown circuitry reduces input supply current to less than 1μA while EN/UVLO is pulled low.

The reset and watchdog timeout periods are both adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable reset operation without false triggering. The open collector RST pins will pull down if the monitored output voltage drops 10% below the programmed value. The LT3688 watchdog timer monitors for watchdog falling edges grouped too close together or too far apart.

The LT3688 is available in 24-Pin TSSOP and 4mm × 4mm QFN packages, each with an exposed pad for low thermal resistance.