Date: 28/08/2009

700mA, 36V step-down regulator IC with power-on reset and watchdog timer

Linear has announced the LT3689, a 700mA, 36V input step-down switching regulator with a power-on reset and watchdog timer.

Key features are,

Input range from 3.6V to 36V, overvoltage lockout protects circuits through 60V transients
85µA IQ at 12VIN to 3.3VOUT
Low ripple burst mode operation allows output ripple <15mVP-P
Programmable power-on reset timer (POR)
Externally synchronizable from 350kHz to 2.2MHz switching frequency
Adjustable output voltage
800mV feedback voltage
Programmable input undervoltage lockout with hysteresis
Features power good flag and soft-start capability

The LT3689 burst mode operation provides low quiescent current, and suitable for applications like automotive or telecom systems.

The reset and watchdog timeout periods are indepedently adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable reset operation of a system without false triggering. The open collector RST will pull down if output voltage drops 10% below the programmed value. The watchdog timer is pin-selectable for window or timeout modes. In timeout mode, WDO pulls low if too long a period passes before a watchdog transition is detected. In window mode, the LT3689 monitors for WDI falling edges grouped too close together or too far apart.

Operating temperature range:
LT3689IUD, LT3689IMSE: -40°C to 125°C
LT3689HMSE: -40°C to 150°C

Package: 16-Pin 3mm × 3mm QFN & 16-Pin MSOP Package
Price:
LT3689EUD: starts at each $3.20 for 1k pieces
LT3689EMSE: starts at each $3.25 for 1k pieces
LT3689IUD: starts at each $3.56 for 1k pieces
LT3689IMSE: starts at each $3.61 for 1k pieces
LT3689HMSE: starts at each $3.86 for 1k pieces

For more details visit www.linear.com