DEMO MANUAL DC2681A-A LTM4645 25A DC/DC Step-Down Module Regulator DESCRIPTION Demonstration circuit 2681A-A features the LTM 4645EY, pulse-skipping mode for noise sensitive applications or a 25A high efficiency, switch mode step-down power burst mode operation in less noise sensitive applications. Module regulator. The input voltage range is from 6V to The MODE PLLIN pin also allows the LTM4645 to syn- 15V. To use DC2681A-A for input voltage range from 4.7V chronize to an external clock signal (between 400kHz and to 6V, connect INTV to SV (change R22 from OPT to 800kHz). DC2681A-A has the option of choosing both CC IN 0), DRV to V (change R21 from 0 to OPT, R28 from internal and external compensation circuit for LTM4645. CC IN OPT to 0). The output voltage range is 0.6V to 1.8V. Tying the PHASMD pin to different voltage generates cer- Derating is necessary for certain V , V , frequency tain phase difference between MODE PLLIN and CLKOUT. IN OUT and thermal conditions. The DC2681A-A offers the TRK/ The LTM4645 data sheet must be read in conjunction with SS pin allowing the user to program output tracking or this demo manual prior to working on or modifying demo soft-start period. The board operates in continuous con- circuit DC2681A-A. duction mode in heavy load conditions. For high efficiency Design files for this circuit board are available. at low load currents, the MODE PLLIN jumper selects All registered trademarks and trademarks are the property of their respective owners. BOARD PHOTO Rev. 0 1DEMO MANUAL DC2681A-A PERFORMANCE SUMMARY PARAMETER CONDITIONS/NOTES VALUE Input Voltage Range 6V to 15V Output Voltages 1.0V 1.0% Maximum Continuous Output Current Derating is Necessary for Certain Operating 25ADC Conditions. See Data Sheet for Details Operating Frequency 600kHz Efficiency V = 12V, V = 1.0V, I = 25A 84.6% Figure 2 IN OUT OUT Load Transient V V = 12V, V = 1.0V, I = 0A to 12.5A 128mV Figure 3 OUT(P-P) IN OUT STEP QUICK START PROCEDURE Demonstration circuit DC2681A-A is an easy way to evalu- 4. Vary the input voltage from 6V to 15V and adjust the ate the performance of the LTM4645EY. Please refer to load current from 0A-25A. Observe the output voltage Figure 1 for proper measurement equipment setup and regulation, ripple voltage, efficiency, and other param- follow the procedure below: eters. 1. Place jumpers in the following positions for a typical 5. (Optional) For optional load transient test, apply an application: adjustable pulse signal between IOSTEP CLK and GND test points. The pulse amplitude sets the load step cur- MODE RUN rent amplitude. Keep the pulse width short (<1ms) and CCM ON pulse duty cycle low (<5%) to limit the thermal stress on the load transient circuit. 2. With power off, connect the input power supply, load and meters as shown in Figure 1. Preset the load to 0A 6. (Optional) LTM4645 can be synchronized to an external and V supply to 12V. IN clock signal. Place the JP1 jumper on EXT CLK and apply a clock signal (0V to 5V, square wave) on the 3. Turn on the power supply at the input. The output volt- MODE PLLIN test point. age should be 1.0V 1.0% (0.99V to 1.01V). Rev. 0 2