QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1483 DUAL 550MA SYNCHRONOUS BOOST CONVERTER LTC3535 DESCRIPTION Demonstration circuit 1483 is a dual high efficiency when shutdown and provides soft start and current synchronous boost converter capable of operating limiting. with an input voltage range from 0.8V to 5V. The 12 This demonstration circuit allows the user to quickly lead 3X3 mm thermally enhanced DFN package with a evaluate the LTC3535 performance. Individual jump- 1MHz switching frequency and the 550mA internal ers are provided for selecting a variety of output volt- switches provide a very tiny step-up solution. The ages from 1.8V to 5V. Jumpers also allow separate LTC3535 can be powered from separate input sup- low quiescent current shutdown and the ability to plies that can be greater or less than the output volt- parallel the inputs. Terminals on the board allow easy age although the efficiency and maximum output cur- hookup to input supplies and output loads. rent is reduced when V is greater than V . Also fea- IN OUT Design files for this circuit board are available. Call tured is burst mode operation for high efficiency at the LTC factory. low current levels and a true input-to-output discon- LTC and Burst Mode are trademarks of Linear Technology Corporation nect which allows the output to drop to zero volts Table 1. Each Converter Typical Specifications (25C) V Input Voltage Range after startup Minimum voltage is load current dependant 0.5V to 5V IN V 3V V = 1.5V, I = 100mA 3V 3% OUT1 IN OUT V 3.3V V = 1.5V, I = 100mA 3.3V 3% OUT1 IN OUT V 5V V = 1.5V, I = 100mA 5.0V 3% OUT1 IN OUT V 1.8V V = 1.5V, I = 100mA 1.8V 3% OUT2 IN OUT V 2.85V V = 1.5V, I = 100mA 2.85V 3% OUT2 IN OUT V 3.3V V = 1.5V, I = 100mA 3.3V 3% OUT2 IN OUT Output Ripple Voltage (burst mode) V = 1.2V, V = 3.3V I = 10mA 45mV p-p IN OUT OUT Output Ripple Voltage (fixed frequency) V = 1.2V, V = 3.3V I = 100mA 15mV p-p IN OUT OUT Efficiency V = 1.2V, V = 1.8V I = 10mA 84% IN OUT OUT Efficiency V = 1.8V, V = 3.3V I = 100mA 88% IN OUT OUT 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1483 DUAL 550MA SYNCHRONOUS BOOST CONVERTER QUICK START PROCEDURE The boost converters can be evaluated using the connections and Ammeter will result in the input setup shown in Figure 1. Set jumper JP1 to the voltage at the input terminals dropping below the PARALLEL position and JP2 and JP3 to ON. Select minimum voltage required for operation. the desired output voltages using jumpers JP4 and Additional pc board pads are provided for optional JP5. (With no jumpers installed, the output voltage input bypass capacitors (C1, C3). These may be is set for the maximum). Connect voltmeters and necessary when using long wires between the ammeters as shown on the test setup. Connect a power supply and circuit board, or for adding tanta- power supply to the V and GND terminals and suit- IN lum capacitors to minimize input voltage transients able load resistors between VOUT and GND. that may occur when the input is hot-switched. With a light load (1k resistor) at one of the outputs, Also, pads on the board backside are provided for begin increasing the input power supply voltage. At adding small Schottky diodes, which can increase approximately 800mV, the output will rise to the efficiency slightly under some conditions. But add- selected regulated voltage. Increase the input volt- ing a diode defeats the output disconnect and short age to approximately 1.5V and increase the load circuit protection features. current. When verifying output ripple use the scope probe Note the excellent load regulation when going from connection as shown in figure 2. a light load current to a heavier load, but it is impor- In Burst mode with light load current, the output tant to monitor the input voltage directly at the in- ripple voltage is higher than in non-burst mode. put terminals of the circuit board. At very low input See the LTC3535 Data Sheet for additional data. voltages, voltage drops in the power supply wire, VOUT2 ON/OFF Select VOUT2 Resistive Voltage Loads VOUT2 ON OFF A Input + A V Power V Supply - Seperate or Parallel Inputs V Converter 1 Input A VOUT1 ON OFF Select VOUT1 VOUT1 Package marking LDWV Voltage ON/OFF Figure 1. Demonstration Circuit Test Setup V OUT GND Figure 2. Scope Probe Placement for Measuring Output Ripple Voltage. 2