Datasheet LTM8026 (Analog Devices) - 12

LTM8026
OPERATION
The LTM8026 is a standalone nonisolated step-down The RUN pin functions as a precision shutdown pin. When switching DC/DC power supply that can deliver up to 5A of the voltage at the RUN pin is lower than 1.55V, switch- output current. This µModule regulator provides a precisely ing is terminated. Below the turn-on threshold, the RUN regulated output voltage programmable via one external pin sinks 5.5µA. This current can be used with a resistor resistor from 1.2V to 24V. The input voltage range is 6V between RUN and VIN to the set a hysteresis. During start- to 36V. Given that the LTM8026 is a step-down converter, up, the SS pin is held low until the part is enabled, after make sure that the input voltage is high enough to support which the capacitor at the soft-start pin is charged with the desired output voltage and load current. an 11µA current source. As shown in the Block Diagram, the LTM8026 contains a The LTM8026 is equipped with a thermal shutdown to current mode controller, power switches, power inductor, protect the device during momentary overload conditions. and a modest amount of input and output capacitance. It is set above the 125°C absolute maximum internal tem- The LTM8026 utilizes fixed frequency, average current perature rating to avoid interfering with normal specified mode control to accurately regulate the inductor current, operation, so internal device temperatures will exceed independently from the output voltage. This is an ideal the absolute maximum rating when the overtemperature solution for applications requiring a regulated current protection is active. So, continuous or repeated activation source. The control loop will regulate the current in the of the thermal shutdown may impair device reliability. internal inductor. Once the output has reached the regula- During thermal shutdown, all switching is terminated and tion voltage determined by the resistor from the ADJ pin the SS pin is driven low. to ground, the inductor current will be reduced by the The switching frequency is determined by a resistor at voltage regulation loop. the RT pin. The LTM8026 may also be synchronized to an The current control loop has two reference inputs, external clock through the use of the SYNC pin. determined by the voltage at the analog control pins, CTL_I and CTL_T . CTL_I is typically used to set the maximum allowable current output of the LTM8026, while CTL_T is typically used with a NTC thermistor to reduce the output current in response to temperature. The lower of the two analog voltages on CTL_I and CTL_T determines the regulated output current. The analog control range of both the CTL_I and CTL_T pin is from 0V to 1.5V. 8026fd 12 For more information www.linear.com/LTM8026 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Package Photo Package Description Revision History Typical Application Design Resources Related Parts