Date: 25/01/2010

Dual channel step-down regulator with power-on reset and watchdog timer

Linear has introduced the LT3640, a new dual channel, current mode step-down switching regulator with a power-on reset and 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 LT3640 regulator is suitable for the industrial power supplies,
Automotive Electronic control unit applications.

The key features of the LT3640 regulator are,

High voltage buck regulator
4V to 35V operating, OVLO protects input to 55V
1.3A of output current
Low voltage synchronous buck regulator
Operating input voltage ranges from 2.5V to 5.5V
1A of output current
Synchronizable, adjustable 350kHz to 2.5MHz switching frequency
16VIN to 3.3VOUT Conversion at 2MHz
Programmable power-on reset timer
Programmable window mode watchdog timer
Low ripple (15mVPK-PK) burst mode operation, quiescent current= 350uA
275µA of quiescent current
Short-circuit robust
Programmable soft-start
Low shutdown current: IQ < 1µA

The LT3640 uses a unique dual channel design with a high input voltage (4VIN to 35VIN, 55VIN transient) nonsynchronous channel that delivers 1.1A of output current, combined with a low input voltage (2.5VIN to 5.5VIN) synchronous channel that provides up to 0.9A of continuous output current.

The LT3640 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 LT3640 implements a windowed watchdog timer monitoring falling edges at its watchdog input pin that are grouped too close together or too far apart.

Operating temperature range: -40°C to 125°C

Package: 4mm x 5mm QFN-28 (or TSSOP-28) package
Price:
LT3640EUFD: Starts at each $3.50 for 1k pieces
LT3640EFE: Starts at each $3.65 for 1k pieces
LT3640IUFD: Each $3.89 for 1k pieces
LT3640IFE: Each $4.06 for 1k pieces

Availability: All versions are available from stock

For more details visit www.linear.com