DEMO CIRCUIT 950A LT3825 AND LT3837 QUICK START GUIDE LT3825 and LT3837 Non-opto Synchronous Fly- back Controller DESCRIPTION Demonstration circuit 950A uses a transformer design Demonstration circuit 950A is a 30W multi-output syn- with tapped secondary winding, to achieve higher effi- chronous flyback converter in 1/8 brick format featuring ciency and better cross regulation than is possible with a the LT3825 and LT3837. Output voltage sensing is im- transformer that uses a separate winding for each out- plemented without the use of opto-coupler, by sensing put. the voltage across a primary side auxiliary winding. A load compensation circuit is used to compensate for Design files for this circuit board are available. Call voltage drops caused by load currents. the LTC factory. L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered DC950A-A has input voltage range 36V-72V and features trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy the LT3825. Drive, FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode Dimming, No Latency , No Latency Delta-Sigma, No R , Operational Filter, PanelProtect, SENSE DC950A-B has input voltage range 9V-36V and features PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names the LT3837. may be trademarks of the companies that manufacture the products. PERFORMANCE SUMMARY Specifications are at TA = 25C SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Input Supply Range DC950A-A 36 72 V IN DC950A-B 9 36 V V Output Voltage V 4.85 5V 5.15 V OUT OUT1 V 3.20 3.3V 3.40 V OUT2 V 2.42 2.5V 2.58 V OUT3 I Output Current (Note: Total output power not to I (5V output) 0 2 4 A OUT OUT1 exceed 30W) I (3.3V output) 0 3 4 A OUT2 I (2.5V output) 0 3 4 A OUT3 Efficiency Efficiency DC950A-A,V =48V,I =2A,I =3A,I =3A 90 % IN OUT1 OUT1 OUT3 DC950A-B,V =24V,I =2A,I =3A,I =3A 89 % IN OUT1 OUT1 OUT3 EQUIPMENT 8 DMMs 1 DC Supply 0-72V 1A for DC950A-A test 1 DC Supply 0-36V 5A for DC950A-B test 3 Adjustable loads 0-3A 1 LT3825 AND LT3837 GETTING STARTED Demonstration circuit 950A is easy to set up to evaluate 3. Check for the proper output voltages. Vout1 = 5V, the performance of the LT3825 and LT3837. Refer to Vout2 = 3.3V, Vout3 = 2.5V. Figure 1 for proper measurement equipment setup and 4. Adjust the loads and study the performance of the follow the procedure below: circuit. Note that the load current should not exceed 4A, and the total load on the three outputs should not exceed 30W continuous power. 1. With power off, connect the input power supply to Vin and GND. 2. With no loads, adjust input voltage to be within the input voltage range (36V-72V for DC950A-A, 9V-36V for DC950A-B) and turn on the power at the input. Figure 1. Proper Measurement Equipment Setup 2