QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 912 BOOST AND INVERTING DC/DC CONVERTERS LT3487EDD DESCRIPTION Demonstration circuit 912 features the LT®3487EDD. The demo circuit demonstrates small size and low component count in a Boost Circuit and an Inverting Circuit. The Boost Converter is designed to convert a 3V-5V input to 15V output at 45mA-90mA maximum load. The Inverting Circuit generates a -8V output at 90mA-150mA maximum load from the same input. Since the maximum Vin of the LT3487EDD is 16V, this Demo circuit will work well at higher inputs. The only limitation is that the input has to be lower than the Boost converter output (15V) in order to stay in regulation. If Vin and VBAT will be powered separately, cut trace as indicated on farside of board and use “VBAT” pad on top. The LT3487EDD features integrated Schottky diodes for both outputs and requires only one resistor (per output) to set the output voltage. Internal sequencing disables switching on the negative supply until the positive has reached 87% of its final value. Both circuits are designed to demonstrate the capacitor programmable Soft-Start feature with a single capacitor, advantages of the 2MHz constant switching frequency and the internal 32V switches. Both outputs on this demo circuit can be modified for higher voltages. These circuits are intended for space-conscious applications such as CCD Bias, TFT LCD Bias, OLED Bias and +/- Rail Generation for Op Amps. Design files for this circuit board are available. Call the LTC factory. LT is a trademark of Linear Technology Corporation Table 1. Performance Summary (TA = 25°C) PARAMETERS FOR 15V BOOST CIRCUIT CONDITION VALUE Minimum Input Voltage 3V Maximum Input Voltage 5V Output Voltage VOUT VIN = 3V, IOUT = 0mA to 45mA 15V ±5% Output Voltage VOUT VIN = 5V, IOUT = 0mA to 90mA 15V ±5% Maximum Output Current Vin = 3V 45mA Maximum Output Current Vin = 5V 90mA Typical Output Ripple VOUT VIN = 3.3V, IOUT = 45mA 20mVP–P Typical Efficiency VIN = 3.6V, Vout = 15V@45mA 77% PARAMETERS FOR -8V INVERTING CIRCUIT VALUE Output Voltage VOUT VIN = 3V, IOUT = 0mA to 90mA -8V ±5% Output Voltage VOUT VIN = 5V, IOUT = 0mA to 150mA -8V ±5% Maximum Output Current Vin = 3V 90mA Maximum Output Current Vin = 5V 150mA Typical Output Ripple VOUT VIN = 3.6V, IOUT = 100mA 10mVP–P Typical Efficiency VIN = 3.6V, Vout = -8V@100mA 70% 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 912 BOOST AND INVERTING DC/DC CONVERTERS QUICK START PROCEDURE Demonstration circuit 912 is easy to set up to evaluate the performance of the LT3487EDD. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the Vin or Vout and GND terminals. See Figure 2 for proper scope probe technique. 1. Place jumpers in the following positions: JP1 On 2. With power off, connect the input power supply to Vin and GND. 3. Turn on the power at the input. 4. Check for the proper output voltages. NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high. 5. Once the proper output voltages are established, adjust the loads within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 912 BOOST AND INVERTING DC/DC CONVERTERS Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 912 BOOST AND INVERTING DC/DC CONVERTERS 4