Datasheet LTM8033 (Analog Devices) - 10

LTM8033
OPERATION
The LTM8033 is a standalone nonisolated step-down To further optimize efficiency, the LTM8033 automatically switching DC/DC power supply that can deliver up to 3A of switches to Burst Mode operation in light load situations. output current. It is an EMC product; its radiated emissions Between bursts, all circuitry associated with controlling are so quiet that it can pass the stringent requirements of the output switch is shut down reducing the input supply EN55022 class B as a stand alone product. This µModule current to 50μA in a typical application. provides a precisely regulated output voltage program- The oscillator reduces the LTM8033’s operating frequency mable via one external resistor from 0.8V to 24V. The input when the voltage at the ADJ pin is low. This frequency voltage range is 3.6V to 36V. Given that the LTM8033 is foldback helps to control the output current during start- a step-down converter, make sure that the input voltage up and overload. is high enough to support the desired output voltage and load current. The LTM8033 contains a power good comparator which trips when the ADJ pin is at roughly 90% of its regulated As shown in the Block Diagram, the LTM8033 contains an value. The PGOOD output is an open-collector transistor EMI filter, current mode controller, power switching ele- that is off when the output is in regulation, allowing an ment, power inductor, power Schottky diode and a modest external resistor to pull the PGOOD pin high. Power good amount of input and output capacitance. The LTM8033 is is valid when the LTM8033 is enabled and V a fixed frequency PWM regulator. The switching frequency IN is above 3.6V. is set by simply connecting the appropriate resistor value from the RT pin to GND. The LTM8033 is equipped with a thermal shutdown that will inhibit power switching at high junction temperatures. An internal regulator provides power to the control circuitry. The activation threshold of this function, however, is above The bias regulator normally draws power from the VIN 125°C to avoid interfering with normal operation. Thus, pin, but if the BIAS pin is connected to an external volt- prolonged or repetitive operation under a condition in age higher than 2.8V, bias power will be drawn from the which the thermal shutdown activates may damage or external source (typically the regulated output voltage). impair the reliability of the device. This improves efficiency. The RUN/SS pin is used to place the LTM8033 in shutdown, disconnecting the output and reducing the input current to less than 1μA. 8033fb 10 For more information www.linear.com/LTM8033 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Package Photographs Revision History Typical Application Related Parts