Date: 19/08/2011

42V input with 55V transient protection, 2MHz dual channel step-down regulator

Linear Technology Corporation has announced a dual channel, current mode step-down switching regulator the LT3641, with a power-on reset and watchdog timer. Its 4V to 42V input voltage range with 55V transient capability makes it suitable for load dump and cold crank conditions commonly found in automotive applications which require constant output regulation even with input transients as high as 55V.

Using a nominal 12V input and a 2MHz switching frequency, the LT3641 can deliver a 3.3V output at 600mA with 85% efficiency via its high voltage channel and a 1.8V output at 800mA with 90% secondary conversion efficiency via its lower voltage channel.

The integrated microprocessor supervisor functions support high reliability applications such as automotive electronic control units. LT3641 includes one power-on reset timer for each channel and one common watchdog timer, the reset and watchdog timeout periods are independently adjustable using external capacitors. Tight accuracy specifications and glitch immunity ensure reliable reset operation of a system without false triggering. The LT3641 implements a windowed watchdog timer monitoring for WDI falling edges grouped too close together or too far apart.

Key features of LT3641 include:
High Voltage Buck Regulator: 4V to 42V Operating Range, with Transient Protection to 55V
1.3A Output Current
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: IQ < 290µA
Short-Circuit Robust
Programmable Soft-Start
Low Shutdown Current: IQ < 1µA
Thermal Shutdown
Available in Thermally Enhanced 28-Lead (4mm x 5mm) QFN &
28-Lead TSSOP Packages

At high inputs voltage of 35V, it can deliver 3.3V and 1.1V outputs using a 2MHz switching frequency, allowing it to avoid critical frequency bands such as AM radio. The LT3641 can deliver output voltages down to 1.26V on its high voltage channel and down to 0.6V on its low voltage channel supporting new generation of processor chips.

Availability and Price: The LT3641EUFD and LT3641EFE are priced starting at $3.58 each for 1,000 piece quantities. The LT3641IUFD and LT3641IFE are tested and guaranteed to operate from a -40°C to 125°C operating junction temperature and are priced at $4.02 each in 1,000 piece quantities.

For more information, visit www.linear.com/product/LT3641.