QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1260A-A/1260A-B 2A SYNCHRONOUS STEP-UP DC/DC CONVERTER LTC3539/3539-2 DESCRIPTION Demonstration circuits 1260A-A and 1260A-B are high and jumpers for low quiescent current shutdown and efficiency synchronous boost converters capable of PWM/BURST mode. Terminals on the board allow operating with an input voltage range from 0.7V to easy hookup to an input supply and output load. 5.5V. The 2X3 mm DFN thermally enhanced package When Burst mode is selected, the converters auto- with a 1MHZ switching frequency (2MHz for the -2 matically enter low quiescent current Burst-Mode op- part) and the 2A internal switches provide a very tiny eration at low current levels, and return to fixed fre- overall solution. The LTC3539/LTC3539-2 also feature quency PWM operation at higher current levels. In output disconnect, selectable PWM or BURST mode PWM mode, the converter operates continuously in operation, Shutdown capability and the input voltage fixed frequency. Design files for this circuit board are available. Call the can be greater or less than the output voltage. LTC factory. This demonstration circuit allows the user to quickly LTC and Burst Mode are trademarks of Linear Technology Corpo- evaluate the LTC3528 performance. Jumpers are pro- ration vided for selecting several regulated output voltages, Table 1. Typical Specifications (25C) V , Input Start-up Voltage 650mV IN V Input Voltage Range (after start-up) 0.5V to 5V IN, 1.8V V V = 1V, I = 100mA 1.8V 2.5% OUT IN OUT 3.3V V V = 1.5V, I = 200mA 3.3V 2.5% OUT IN OUT 5V V V = 1.5V, I = 200mA 5.0V 2.5% OUT IN OUT Output Ripple Voltage (burst mode) V = 1.5V, V = 3.3V I = 3mA 8mV p-p IN OUT OUT Output Ripple Voltage (fixed frequency) V = 1.5V, V = 3.3V I = 300mA 15mV p-p IN OUT OUT Efficiency V = 1.8V, V = 3.3V I = 100mA 90% IN OUT OUT Resistive Load - Input V Power V Supply + A 0 to 5V 3A A Figure 1. Demonstration Circuit Test Setup 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1260A-A/1260A-B 2A SYNCHRONOUS STEP-UP DC/DC CONVERTER Demo Part Part Marking Frequency 1260A-A LTC3539EDCB LDCS 1 MHz 1260A-B LTC3539EDCB-2 LDPH 2 MHz Table 1. Demonstration Circuit Board Information QUICK START PROCEDURE There is one demonstration circuit board for both the output voltage ripple will increase as Vin ap- LTC3539 versions. The boards are identified by the proaches Vout. The increase will occur in a narrow handwritten information on the top of the pc board. range when Vin is between 100 and 300mV below The boost converter can be evaluated using the Vout. The ripple voltage in this range can be from setup shown in Figure 1. Select one of the three out- 30mV to 100mV pp. put voltages using the voltage select jumpers. (With When evaluating the circuit at very low input volt- no jumper installed, the output voltage is 5V.) With ages, it is important to monitor the input voltage di- jumper JP2 in the ON position and JP1 in BURST, rectly at the input terminals of the circuit board. At connect voltmeters and ammeters as shown on the these low input voltages, any voltage drop in the power supply wire, connections and Ammeter will test setup. Connect a power supply to the +V and IN result in the input voltage at the input terminals GND terminals and a suitable load resistor between dropping below the minimum voltage required for VOUT and GND. operation. With a light load (1k resistor) at the output, begin Additional pc board pads are provided for an optional increasing the input power supply voltage. At ap- input bypass capacitor (C1). It maybe necessary proximately 650mV, the output will rise to the se- when using long wires between the power supply lected regulated voltage. When the output voltage and circuit board, or for adding a tantalum capacitor exceeds the input voltage by at least 240mV, the to minimize input voltage transients that may occur converter powers itself from the output instead of when the input is hot-switched. Additional pads di- the input. This feature allows the input voltage to rectly above the output capacitor (C4) are provided if drop as low as 500mV (at light loads) and still main- additional output capacitance is needed. tain a regulated output voltage. When verifying output ripple, it is important to use Increase the input voltage to approximately 1.5V and the scope probe connection as shown in figure 3. increase the load current. The maximum load current Typical output voltage ripple with a 1k and 100-Ohm depends on the input and output voltage settings. load are shown in figure 2. The 1k load shows Burst Refer to the data sheet curves for typical output cur- mode ripple, while the 100 Ohm load is fixed fre- rent for various input/output voltages. quency PWM mode. The input voltage can exceed the output voltage and See LTC3539/3539-2 Data Sheet for additional information still maintain regulation, although the load current is less and efficiency is lower. It should be noted that 2