Datasheet LT3640 (Analog Devices)

LT3640 Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer FeaTures DescripTion n
High Voltage Buck Regulator:
The LT®3640 is a dual channel, current mode monolithic
4V to 35V Operating Range
buck switching regulator with a power-on reset and a
1.3A Output Current
watchdog timer. Both regulators are synchronized to a n
OVLO Protects Input to 55V
single oscillator with an adjustable frequency (350kHz to n
Low Voltage Synchronous Buck Regulator:
2.5MHz). At light loads, both regulators operate in low
2.5V to 5.5V Input Voltage Range
ripple Burst Mode® to maintain high efficiency and low
1.1A Output Current
output ripple. n
Synchronizable, Adjustable 350kHz to 2.5MHz
The high voltage channel is a nonsynchronous buck with
Switching Frequency
an internal 2.4A top switch that operates from an input n
Programmable Power-On Reset Timer
of 4V to 35V; a 36.5V OVLO protects the device to 55V. n
Programmable Window Mode Watchdog Timer
The low voltage channel operates from an input of 2.5V to n Typical Quiescent Current: 290µA 5.5V. Internal synchronous power switches provide high n Short-Circuit Robust efficiency without the need of external Schottky diode. n Programmable Soft-Start Both channels have cycle-by-cycle current limit, providing n Low Shutdown Current: IQ < 1µA protection against shorted outputs. n Available in Thermally Enhanced 28-Lead (4mm × 5mm) QFN and 28-Lead TSSOP Packages 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 applicaTions too close together or too far apart. n Industrial Power Supplies The LT3640 is available in a 28-pin 4mm × 5mm QFN n Automotive Electronic Control Units package and 28-pin TSSOP package. Both packages have 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 an exposed pad for low thermal resistance. property of their respective owners. Typical applicaTion
2MHz 3.3V/0.8A and 1.8V/0.8A Step Down Regulators HV Channel Efficiency, LV Channel Efficiency,
0.22µF
2MHz, V 2MHz, V
V
OUT1 = 3.3V OUT2 = 1.8V
IN 5V TO 35V 10µF 3.3µH 90 90 VOUT1 EN/UVLO VIN SW BST SW1 3.3V/0.8A V SYNC IN2 = 3.3V 80.6k WDE DA 22µF 85 85 PGOOD FB1 VIN = 12V VOUT1 49.9k 100k 100k 80 80 RST1 LT3640 VIN2 RST2 EN2 µP EFFICIENCY (%) EFFICIENCY (%) WDO 1µH VOUT2 WDI SW2 1.8V/0.8A 75 75 100k 22µF CWDT FB2 CPOR RT GND SS2 SS1 49.9k 70 70 0 0.2 0.4 0.6 0.8 1.0 1.2 0 0.2 0.4 0.6 0.8 1 1.5nF 1.5nF 1nF V V 32.4k 1nF OUT1 CURRENT (A) OUT2 CURRENT (A) 3640 TA01b 3640 TA01c 3640 TA01a 3640f Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Timing Diagrams Operation Applications Information Typical Applications Package Description Typical Application Related Parts