DC968A-B Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 968A-B ISOLATED DC/DC POWER CONVERTER LT1952 DESCRIPTION Demonstration circuit 968A-B is isolated input to high efficiency. Therefore, narrow input voltage range will current output 1/8th Brick footprint converter featur- be more desirable. ing the LT 1952 switching controller. The DC968 The DC968 circuit features soft-start which prevents converts isolated 18V to 36V input to 5V output and output voltage overshoot on startup or when recover- provides over 20A of output current. The converter ing from overload condition. operates at 300kHz with efficiency greater than 93%. The DC968 has precise over-current protection circuit The DC968 can be easily modified to generate output that allows for continuous operation under short cir- voltages in the range from 0.6V to 28V. The output cuit conditions. The low power dissipation under currents are limited by total output power of up to short circuit conditions insures high reliability even 200W. The other available versions of DC968A are: during short circuits. DC968A-A 36-75Vin to 3.3V 30A The LT1952 can be synchronized to an external clock DC968A-C 36-75Vin to 12V 12A of up to 400kHz. Please refer to LT1952 data sheet for DC968A-D 36-75Vin to 28V 4A design details and applications information. Also, the DC968 can be modified for other input volt- Design files for this circuit board are available. Call ages like 8V-36V, 18V-75V, 44V-52V, and so on. The the LTC factory. wider input voltage range will decrease the converter LT is a trademark of Linear Technology Corporation Table 1. Performance Summary PARAMETER CONDITION VALUE Minimum Input Voltage I = 0A to 20A 18V OUT Maximum Input Voltage I = 0A to 20A 36V OUT V V = 18V to 36V, I = 0A to 20A 5V 3% OUT IN OUT Typical Output Ripple V V = 18V to 36V, I = 0A to 20A 50mV OUT IN OUT PP Nominal Switching Frequency 300kHz QUICK START PROCEDURE Demonstration circuit 968 is easy to set up to evalu- across the Vin or Vout and GND terminals. See Figure ate the performance of LT1952 circuit. Refer to Fig- 2. for proper scope probe technique. ure 1 for proper measurement equipment setup and 1. With power off, connect the input power supply to follow the procedure below: Vin and GND. Make sure that the input power sup- NOTE: When measuring the input or output voltage ply has sufficient current rating at minimum input ripple, care must be taken to avoid a long ground lead voltage for the required output load. on the oscilloscope probe. Measure the input or out- 2. Turn on the power at the input. put voltage ripple by touching the probe tip directly 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 968A-B ISOLATED DC/DC POWER CONVERTER NOTE: Make sure that the input voltage does not serve the output voltage regulation, ripple voltage, exceed 40V. efficiency and other parameters. 3. Check for the proper output voltage. 5. The DC968 is equipped with an output capacitor Vout = 5V. CSYS (470uF) that approximates typical system rail capacitance. If system board already has ca- If there is no output, temporarily disconnect the pacitance of similar value CSYS can be removed. load to make sure that the load is not set too high. 4. Once the proper output voltage is established, ad- just the load within the operating range and ob- Figure 1. Proper Measurement Equipment Setup 2