QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-B ACTIVE RESET ISOLATED 18-72V INPUT TO 5V 25A DC/DC POWER CONVERTER LT1952 DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN Demonstration circuit 1317A-B is isolated input to DC1317A-D, 18-72Vin to 24V, 5A high current output 1111////8888tttthhhh BBBBrrrriiiicccckkkk ffffoooooooottttpppprrrriiiinnnntttt converter DC1317A-E, 36-72Vin to 5V, 12A featuring the LT 1952 switching controller with Ac- DC1317A-F, 9-36Vin to 3.3V, 20A tive Reset circuit. The Active Reset circuit can im- prove the efficiency in wide input voltage applica- DC1317A-G, 9-36Vin to 12V, 5A tions. Also, the Active Reset allows the implementa- DC1317A-H, 9-36Vin to 48V, 1.5A tion of self-driven synchronous secondary rectifiers in some applications. The DC1317A-B converts isolated wide 18V to 72V The DC1317 circuit features soft-start which prevents input to 5V output and provides over 30A of output output voltage overshoot on startup or when recover- current depending on cooling. When determining the ing from overload condition. cooling requirements the actual input voltage range The DC1317 has precise over-current protection cir- and continuous maximum output current must be cuit that allows for continuous operation under short taken into account. The converter operates at 200kHz circuit conditions. The low power dissipation under with the peak efficiency greater than 94%. The short circuit conditions insures high reliability even DC1317 can be easily modified to generate output during short circuits. voltages in the range from 0.6V to 48V. The output currents are limited by total output power of up to The LT1952 can be synchronized to an external clock 150W. of up to 400kHz. Please refer to LT1952 data sheet for design details and applications information. The available versions of DC1317A are: DDDDeeeessssiiiiggggnnnn ffffiiiilllleeeessss ffffoooorrrr tttthhhhiiiissss cccciiiirrrrccccuuuuiiiitttt bbbbooooaaaarrrrdddd aaaarrrreeee aaaavvvvaaaaiiiillllaaaabbbblllleeee.... DC1317A-A, 34-75Vin to 3.3V, 35A CCCCaaaallllllll tttthhhheeee LLLLTTTTCCCC ffffaaaaccccttttoooorrrryyyy.... DC1317A-B, 18-72Vin to 5V, 25A LT is a trademark of Linear Technology Corporation DC1317A-C, 18-72Vin to 12V, 10A TTTTaaaabbbblllleeee 1111.... PPPPeeeerrrrffffoooorrrrmmmmaaaannnncccceeee SSSSuuuummmmmmmmaaaarrrryyyy PPPPAAAARRRRAAAAMMMMEEEETTTTEEEERRRR CCCCOOOONNNNDDDDIIIITTTTIIIIOOOONNNN VVVVAAAALLLLUUUUEEEE Minimum Input Voltage I = 0A to 25A 18V OUT Maximum Input Voltage I = 0A to 25A 72V OUT V V = 18V to 72V, I = 0A to 25A 5V 3% OUT IN OUT (30Amax) Typical Output Ripple V V = 18V to 72V, I = 0A to 25A 50mV OUT IN OUT PP Nominal Switching Frequency 200kHz 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-B ACTIVE RESET ISOLATED 18-72V INPUT TO 5V 25A DC/DC POWER CONVERTER QQQQUUUUIIIICCCCKKKK SSSSTTTTAAAARRRRTTTT PPPPRRRROOOOCCCCEEEEDDDDUUUURRRREEEE Demonstration circuit 1317 is easy to set up to evalu- 3333.... Check for the proper output voltage. ate the performance of LT1952 circuit. RRRReeeeffffeeeerrrr ttttoooo FFFFiiiigggg---- Vout = 5V. uuuurrrreeee 1111 ffffoooorrrr pppprrrrooooppppeeeerrrr mmmmeeeeaaaassssuuuurrrreeeemmmmeeeennnntttt eeeeqqqquuuuiiiippppmmmmeeeennnntttt sssseeeettttuuuupppp If there is no output, temporarily disconnect the and follow the procedure below: load to make sure that the load is not set too high. NNNNOOOOTTTTEEEE:::: When measuring the input or output voltage 4444.... Once the proper output voltage is established, ad- ripple, care must be taken to avoid a long ground lead just the load within the operating range and ob- on the oscilloscope probe. Measure the input or out- serve the output voltage regulation, ripple voltage, put voltage ripple by touching the probe tip directly efficiency and other parameters. across the Vin or Vout and GND terminals. See Figure 5555.... The DC1317 is equipped with an output capacitor 2. for proper scope probe technique. CSYS (470uF) that approximates typical system 1111.... With power off, connect the input power supply to rail capacitance. If system board already has ca- Vin and GND. Make sure that the input power sup- pacitance of similar value CSYS can be removed. ply has sufficient current rating at minimum input voltage for the required output load. 2222.... Turn on the power at the input. NNNNOOOOTTTTEEEE:::: Make sure that the input voltage does not exceed 72V. 2