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