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