QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 925 TRIPLE OUTPUT TFT LCD BIAS SUPPLY LT3489EMS8E DESCRIPTION Demonstration circuit 925 features the LT3489EMS8E This circuit is designed to demonstrate the capacitor in a circuit specifically designed to drive large programmable Soft-Start feature, advantages of the TFT/LCD displays. The demo circuit demonstrates 2MHz constant switching frequency and the internal small size and low component count in a Boost Cir- 2.5A, 40V switch. This circuit is intended for large cuit. It converts a 3.3V-6V input to 8V at 600mA, 23V TFT-LCD displays and other space-conscious applica- at 10mA and -8V at 20mA. Since the maximum Vin of tions such as Bias Supplies, GPS Receivers, DSL the LT3489 is 16V, this Demo circuit will work well at Modems and Local Power Supplies. higher inputs. The only limitation is that the input has Design files for this circuit board are available. Call to be lower than the Boost converter output (8V) in the LTC factory. order to stay in regulation. LT is a trademark of Linear Technology Corporation Table 1. Performance Summary (T = 25C) A PARAMETERS FOR 15V BOOST CIRCUIT CONDITION VALUE Minimum Input Voltage 3.3V Output Voltage V V = 3.3V, I = 0mA to 600mA 8V 3% OUT IN OUT Maximum Output Current for 8V Output Vin = 3.3V, 23V 10mA and -8V 20mA 600mA Typical Output Ripple V for 8V Output V = 3.3V , I = 600mA 30mV OUT IN OUT PP V = 3.3V, Vout = 8V 400mA, -8V 20mA, IN Typical Efficiency All Outputs Loaded 83% 23V 10mA QUICK START PROCEDURE Demonstration circuit 925 is easy to set up to evalu- 2. With power off, connect the input power supply to ate the performance of the LT3489EMS8E. 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 1 GND VIN QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 925 TRIPLE OUTPUT TFT LCD BIAS SUPPLY Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2