DC1537A

DEMO MANUAL DC1537A LT3992A Monolithic Dual Tracking 3A Step-Down Switching Regulator DESCRIPTION Both converters are synchronized to either a common external clock input or a resistor programmable 250kHz to 2MHz internal oscillator. At all frequencies, a 180° phase shift between channels is maintained, reducing voltage ripple. Programmable frequency allows optimization between efficiency and external component size. Each output can be independently disabled using its own SHDN pin and be placed in a low quiescent current shutdown mode. The LT3992 data sheet gives complete description of the device, operation and application information. The data PERFORMANCE SUMMARY PARAMETER sheet must be read in conjunction with this quick start guide for demo circuit 1537A. Design files for this circuit board are available at http://www.linear.com/demo 100 95 90 EFFICIENCY (%) The demo circuit 1537A is a dual current mode PWM step-down DC/DC converter featuring LT®3992. The demo circuit is designed for 5V and 3.3V outputs from a 7V to 60V input. The current capability of each channel is up to 3A when running individually and 2A when both are sourcing the same current without special heat sinking. Individual soft-start, current limit, comparator, input voltage for each output as well as frequency division and synchronous and clock output functions simplify the complex design of dual-output power converters 85 80 75 70 65 VOUT1 = 5V VOUT2 = 3.3V 60 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 LOAD CURRENT FOR SIGNAL CHANNEL (A) DC1537a F01 Figure 1. Single Channel Efficiency at VIN = 24V, f = 300kHz L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Specifications are at TA = 25°C. CONDITIONS VALUE Minimum Input Voltage 7V Maximum Input Voltage 60V (For Transient. Continuous Operation if D3 and D4 Are Replaced with Higher Voltage Rated Schottky Diodes) Output Voltage VOUT1 VIN = 7~ 60V Output Voltage VOUT2 VIN = 7~ 60V Switching Frequency 5.0V ±3% 3.3V ±3% 300kHz ±10% Maximum Output Current IOUT1 VIN = 7~ 60V 3A Individually, 2A Both Running Maximum Output Current IOUT2 VIN = 7~ 60V 3A Individually, 2A Both Running Voltage Ripple VOUT1 VIN = 12V, IOUT1 = 3A