Datasheet LTM8028 (Analog Devices) - 10

LTM8028
applicaTions inForMaTion
For most applications, the design process is straight verify proper operation over the intended system’s line, forward, summarized as follows: load and environmental conditions. Bear in mind that the 1. Look at Table 1 and find the row that has the desired maximum output current is limited by junction tempera- input range and output voltage. ture, the relationship between the input and output voltage magnitude and polarity and other factors. Please refer to 2. Apply 10μF to VIN and the recommended RT value the graphs in the Typical Performance Characteristics (RT(OPTIMAL) in Table 1). Lower RT values (resulting in section for guidance. a higher operating frequency) may be used to reduce the output ripple. Do not use values below R The maximum frequency (and attendant RT value) at T(MIN). which the LTM8028 should be allowed to switch is given 3. Apply a parallel combination of a 100μF ceramic and in Table 1 in the fMAX column, while the recommended a 470μF electrolytic to BKV. The Sanyo OS-CON 6SEP- frequency (and RT value) for optimal efficiency over the C470M or United Chemi-Con APXF6R3ARA471MH80G given input condition is given in the fOPTIMAL column. work well for the electrolytic capacitor, but other devices There are additional conditions that must be satisfied if with an ESR about 10mΩ may be used. the synchronization function is used. Please refer to the 4. Apply a minimum of 37μF to V Synchronization section for details. OUT. As shown in Table 1, this is usually a parallel combination of 4.7μF, 10μF and 22μF capacitors.
Programming Output Voltage
5. Apply an additional 100µF capacitor to V Three tri-level input pins, VO2, VO1 and VO0, select the value OUT if very small (2%) transient response is required. of output voltage. Table 2 illustrates the 3-bit digital word- to-output voltage resulting from setting these pins high, While these component combinations have been tested low or allowing them to float. These pins may be tied high for proper operation, it is incumbent upon the user to or low by either pin-strapping them to VOB or driving them
Table 1: Recommended Component Values and Configuration (TA = 25°C) VIN VOUT fOPTIMAL RT(OPTIMAL) fMAX RT(MIN)
6V to 36V 0.8V 200kHz 200k 250kHz 165k 6V to 36V 1.0V 250kHz 165k 280kHz 150k 6V to 36V 1.2V 250kHz 165k 315kHz 133k 6V to 36V 1.5V 250kHz 165k 333kHz 127k 6V to 36V 1.8V 315kHz 133k 385kHz 107k 9V to 15V 0.8V 250kHz 165k 650kHz 61.9k 9V to 15V 1.0V 280kHz 150k 750kHz 53.6k 9V to 15V 1.2V 300kHz 143k 800kHz 49.9k 9V to 15V 1.5V 315kHz 133k 1MHz 40.2k 9V to 15V 1.8V 350kHz 118k 1MHz 40.2k 18V to 36V 0.8V 200kHz 200k 250kHz 165k 18V to 36V 1.0V 250kHz 165k 280kHz 150k 18V to 36V 1.2V 250kHz 165k 315kHz 133k 18V to 36V 1.5V 250kHz 165k 333kHz 127k 18V to 36V 1.8V 315kHz 133k 385kHz 107k CIN: 10µF, 50V, 1210 CBKV: 100µF, 6.3V, 1210 + 470µF, 6.3V Low ESR Electrolytic COUT: 4.7µF, 4V, 0603 + 10µF, 10V, 0805 + 22µF, 10V, 0805 COUT (Optional): 100µF, 6.3V, 1210 Note: An input bulk capacitor is required. 8028fb 10 For more information www.linear.com/LTM8028 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 Photo Revision History Typical Application Related Parts