QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-F ACTIVE RESET ISOLATED 9-36V INPUT TO 3.3V 20A DC/DC POWER CONVERTER LT1952-1 DESCRIPTION Demonstration circuit 1317A-F is isolated input to DC1317A-D, 18-72Vin to 24V, 5A high current output 1/8th Brick footprint 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-F converts isolated 9V to 36V input to The DC1317 circuit features soft-start which prevents 3.3V output and provides over 22A of output current output voltage overshoot on startup or when recover- depending on cooling. When determining the cooling ing from overload condition. requirements the actual input voltage range and con- The DC1317 has precise over-current protection cir- tinuous maximum output current must be taken into cuit that allows for continuous operation under short account. The converter operates at 200kHz with the circuit conditions. The low power dissipation under peak efficiency greater than 92%. The DC1317 can be short circuit conditions insures high reliability even easily modified to generate output voltages in the during short circuits. range from 0.6V to 48V. The output currents are lim- ited by total output power of up to 150W. The LT1952 can be synchronized to an external clock of up to 400kHz. Please refer to LT1952 data sheet for The available versions of DC1317A are: design details and applications information. DC1317A-A, 34-75Vin to 3.3V, 35A Design files for this circuit board are available. Call DC1317A-B, 18-72Vin to 5V, 25A the LTC factory. DC1317A-C, 18-72Vin to 12V, 8A-12A LT is a trademark of Linear Technology Corporation Table 1. Performance Summary PARAMETER CONDITION VALUE Minimum Input Voltage I = 0A to 22A 9V OUT Maximum Input Voltage I = 0A to 22A 36V OUT V V = 9V to 36V, I = 0A to 22A 3.3V 3% OUT IN OUT (27Amax) Typical Output Ripple V V = 9V to 36V, I = 0A to 22A 50mV OUT IN OUT PP Nominal Switching Frequency 200kHz 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-F ACTIVE RESET ISOLATED 9-36V INPUT TO 3.3V 20A DC/DC POWER CONVERTER QUICK START PROCEDURE Demonstration circuit 1317 is easy to set up to evalu- NOTE: Make sure that the input voltage does not ate the performance of LT1952-1 circuit. Refer to Fig- exceed 36V. ure 1 for proper measurement equipment setup and 3. Check for the proper output voltage. follow the procedure below: Vout = 3.3V. NOTE: When measuring the input or output voltage If there is no output, temporarily disconnect the ripple, care must be taken to avoid a long ground lead load to make sure that the load is not set too high. on the oscilloscope probe. Measure the input or out- 4. Once the proper output voltage is established, ad- put voltage ripple by touching the probe tip directly just the load within the operating range and ob- across the Vin or Vout and GND terminals. See Figure serve the output voltage regulation, ripple voltage, 2. for proper scope probe technique. efficiency and other parameters. 1. With power off, connect the input power supply to 5. The DC1317 is equipped with an output capacitor Vin and GND. Make sure that the input power sup- CSYS (470uF) that approximates typical system ply has sufficient current rating at minimum input rail capacitance. If system board already has ca- voltage for the required output load. pacitance of similar value CSYS can be removed. 2. Turn on the power at the input. Figure 1. Proper Measurement Equipment Setup 2