QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1129A SYNCHRONOUS STEP-DOWN DC/DC CONVERTER LTC3610EWP DESCRIPTION Demonstration circuit DC1129A is a synchronous step eliminates external sensing resistor and improves sup- down converter featuring the LTC 3610, the high effi- ply efficiency. ciency, high density DC/DC regulator. The input volt- Discontinuous mode operation and continuous mode at age range is from 4.5V to 24V. The output voltage is light load is also jumper selectable. A forced continuous jumper selectable from 1.2V to 2.5V. The rated load control reduces noise and RF interference while discon- current is 12A. The regulator includes the controller tinuous control provides high efficiency at light loads. and power MOSFETs in the 9mm by 9 mm QFN pack- age. Design files for this circuit board are available. The constant on time valley mode current control struc- Call the LTC Factory. ture delivers very low duty cycle with excellent load transient response. The MSFET RDS(on) sensing , LTC and LT are registered trademarks of Linear Technology Corporation. Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Minimum Input Voltage 4.5V Maximum Input Voltage 24V Output Voltage V Jumper selectable (open for 0.6V) 1.2V, 1.5V, 1.8V, 2.5V 2% OUT Maximum Continuous Output Current De-rating is necessary for certain V , V , and thermal IN OUT 12A DC conditions, see datasheet Operating Frequency Programmable 750kHz Efficiency V =12V, V =1.5V, I =12A 83%, See Figure 3 IN OUT OUT Load Transient V =12V, V =1.5V See Figure 5 IN OUT 2. With power off, connect the input power sup- QUICK START PROCEDURE ply, load and meters as shown in Figure 1. Preset the load to 0A and Vin supply to be Demonstration circuit DC1129A is easy to set up to less than 24V. evaluate the performance of the LTC3610. Please re- fer to Figure 1 for proper measurement equipment 3. Turn on the power at the input. The output setup and follow the procedure below: voltage should be 1.5V 2%. 4. Once the proper output voltage is established, 1. Place jumpers in the following positions for a adjust the load within the operating range and typical 1.5V application: OUT observe the output voltage regulation, ripple voltage, efficiency and other parameters. Vout Select RUN FCB Output ripple should be measured across the output bulk capacitor as shown in Figure 2. 1.5V ON CCM 5. For optional load transient test, apply adjust- able pulse signal between IOSTEP CLK and GND pins. Pulse amplitude sets the current Preliminary 1 Load 0 -12A QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1129A SYNCHRONOUS STEP-DOWN DC/DC CONVERTER step. The pulse signal should have very small nector J6 (5mV/A). Output voltage transient duty cycle (<5%) to limit the thermal stress response should be measured at J5 with a on the transient load circuit. The output tran- BNC cable. sient current can be monitored at BNC con- Iout + Iin A + A V Vout Vin V Optional 5V Bias Figure 1. Test Setup of DC1129A (EXTVCC Bias Supply is Optional) ++ IInnppuutt oorr OOuuttppuutt CCaappaacciittoorr Figure 2. Scope Probe Placements for Measuring Input or Output Ripple. Preliminary 2 + + + +