LT3640

1

3640p

TYPICAL APPLICATION

DESCRIPTION

Dual Monolithic Buck

Regulator with Power-On

Reset and Watchdog Timer

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

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 36V; a 38V 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.

2MHz 3.3V/0.8A and 1.8V/0.8A Step Down Regulators

FEATURES

APPLICATIONS

4V to 36V Operating Range

1.3A Output Current

2.5V to 5.5V Input Voltage Range

1A Output Current

Switching Frequency

(4mm

× 5mm) QFN and 28-Lead TSSOP Packages

3640 TA01a

SYNC

WDE

PGOOD

1nF

1nF

1.5nF

1.5nF

32.4k

1.8V/0.8A

3.3V/0.8A

47μF

10μF

100k

RST2

EN2

WDO

WDI

FB2

CWDT

CPOR

RT GND SS2

SS1

RST1

SW2

SW1

5V TO 34V

SW

LT3640

BST

FB1

1μH

100k

μP

100k

49.9k

80.6k

49.9k

3.3μH

0.22μF

DA

10μF

22μF

HV Channel Efficiency,

L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks

and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the

property of their respective owners.

LV Channel Efficiency,

0

70

80

0.2

0.4

0.8

0.6

1.0

90

75

85

1.2

3640 TA01b

0

70

80

0.2

0.4

0.8

0.6

1

90

75

85

3640 TA01c

Electrical Specifications Subject to Change